Answer:
A chemical reaction that has a positive δG is best described as non-spontaneous.Explanation:
G is the symbol used for the Gibss energy, also known as free energy.
G measures the useful energy, i.e. the energy that can be used to perform a work.
G = H - TS and the change in G is given by δG = δH - TδS.
The sign of δG tells if a chemical reaction is spontaneous or not.
If δG is positive the reaction is non-spontaneous, if δG is negative the reaction is spontaneous, and if δG = 0 the reaction is at equilibrium. This can be written as:
δG < 0 spontaneous reactionδG = 0 equilibriumδG > 0 non spontaneous reactionThen, as to the given statement, it is completed with the term non-spontaneous, which corresponds to the description of a chemical reaction that has a positive δG.
Which type of substance ionizes completely and creates hydronium ions when dissolved in water?
Answer:
Strong acids.
Explanation:
Acid is a substance that produces hydronium ions (H₃O⁺) when dissolved in water. Acids have a pH less than 7.The degree of hydronium ions (H₃O⁺) depends on the strength of the acid.Strong acids are completely ionized and produce hydronium ions (H₃O⁺).HA + H₂O → H₃O⁺ + A⁻.
Weak acids are partially ionized and produce hydronium ions (H₃O⁺).
HA + H₂O ⇄ H₃O⁺ + A⁻.
Answer: strong acids
Explanation: for one the substance dissolves completely and acids only produce hydronium ions just like acids produce hydroxide ions.
Which volume of 2.0 M NaOH(aq) is needed to completely neutralize 24 milliliters of 1.0 M HCl(aq)?
Answer:
12mLd
Explanation:
Given parameters:
Concentration of base, NaOH = 2.0M
Volume of acid, HCl = 24mL = 24 x 10⁻³L = 0.024L
Concentration of HCl = 1.0M
Unknown parameter
Volume of NaOH = ?
The equation of the reaction is NaOH + HCl → NaCl + H₂O
Method
1. Starting the known values, we find the number of moles of acid used. From the reaction equation , we know that:
1 mole of NaOH reacts with 1 mole of HCl
We use the above to find the number of moles of base used
2. From the number of moles of base, we plug it into the equation below:
Volume of NaOH = [tex]\frac{number of moles of NaOH}{concentration of NaOH}[/tex]
Solution
Number of moles of acid = concentration of acid x volume of acid
Number of moles = 1M x 0.024L = 0.024mol
From the balanced equation we know that:
1 mole of NaOH reacts with 1 mole of HCl
Therefore, the number of moles of NaOH is 0.024mol
Using the equation below, we have:
Volume of NaOH = [tex]\frac{number of moles of NaOH}{concentration of NaOH}[/tex]
Volume of NaoH = [tex]\frac{0.024mol}{2.0M}[/tex]
Volume of NaOH = 0.012L = 12mL
Which one goes where? Thanks!
It's in a file. ⬇
1 -> theory
2-> law
3-> hypothesis
Hydrogen gas has a density of , and at normal pressure and one mole of it takes up . how would you calculate the moles in of hydrogen gas? set the math up. but don't do any of it. just leave your answer as a math expression. also, be sure your answer includes all the correct unit symbols.
To calculate the moles in 5L of hydrogen gas at STP, divide the volume in liters by the volume occupied by one mole of any gas at STP, which is 22.4 L/mol.
To calculate the number of moles in 5L of hydrogen gas at standard temperature and pressure (STP), you can apply the ideal gas law. To set up the calculation, use that at STP, 1 mole of a gas occupies 22.4 L. Use the following mathematical expression for your conversion:
Number of moles = Volume of gas (L) / Volume of 1 mole at STP (L/mol)
For your specific question:
Number of moles of H2 = 5 L / 22.4 L/mol
Make sure to leave your answer as a math expression with the correct units of L for liters and mol for moles.
What is the term for the direction and angle of a handwriting sample?
A) fluidity
B) lift
C) slant
D) spacing
Answer:
slant
Explanation:
The unit meter per second per second (m/s²) would be used to measure
A) acceleration
B) rate of change
C) speed
D) velocity
Answer:
[tex]\boxed{\text{A) Acceleration}}[/tex]
Explanation:
m/s is the unit for speed, so (m/s)/s is the rate of change of speed.
The rate of change of speed is acceleration.
B), C), and D) are wrong. They all have the units of m/s.
How is the equilibrium constant of a reaction determined?
Answer:
The molarity of products is divided by the molarity of reactants.
Explanation:
Carbohydrates are nutrients that supply the main energy source for the body. True or False
Answer:
false
Explanation:
C3H8 + 5O2 → 3CO2 + 4 H2O
How many moles of C3H8 must be reacted to form exactly 10.0 g of H2O?
0.139 mol
0.250 mol
40.0 mol
0.400 mol
Answer:
0.139
Explanation:
First find how many moles of h2o give you 10g then use the mole ratio to find what mole of c3h8 is required to get you that number of moles
Answer:
0.139 moles of C3H8 must be reacted to form exactly 10.0 g of H2O
Explanation:
The rule of three or is a way of solving problems of proportionality between three known values and an unknown value, establishing a relationship of proportionality between all of them. That is, what is intended with it is to find the fourth term of a proportion knowing the other three. Remember that proportionality is a constant relationship or ratio between different magnitudes.
If the relationship between the magnitudes is direct, that is, when one magnitude increases, so does the other (or when one magnitude decreases, so does the other) , the direct rule of three must be applied. To solve a direct rule of three, the following formula must be followed:
a ⇒ b
c ⇒ x
[tex]x=\frac{c*b}{a}[/tex]
It is possible to use the reaction stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) and the rule of three to determinate the moles of C₃H₈ that must be reacted to form exactly 10.0 g of H₂O. But first you must know the amount of moles that represent the 10 g of H₂O.
You know that:
O= 16 g/molH=1 g/molThen, the mass of H₂O is 2*1 g/mol + 16 g/mol= 18 g/mol
Then it is possible to apply a rule of three: if 1 mole of H₂O contains 18 grams, how many moles will contain 10 grams?
[tex]moles of H2O=\frac{10 grams*1 mole}{18 grams}[/tex]
moles of H₂O=0.556
Then, to determine the moles of C₃H₈ that must react to form exactly 10.0 g of H₂O it is possible to use a rule of three, as previously mentioned: if by stoichiometry 4 moles of H₂O are formed from 1 moles of C₃H₈, when are formed 0.55 moles of H₂O How many moles of C₃H₈ will be needed?
[tex]moles of C3H8=\frac{0.556molesofH2O*1molesofC3H8}{4molesofH2O}[/tex]
moles of C₃H₈= 0.139
Finally, 0.139 moles of C3H8 must be reacted to form exactly 10.0 g of H2O
Chemistry help??
A student increases the temperature of a 100 cm3 balloon from 60°C to 120°C. What will the new volume of the balloon be? (Be careful with units.)
(a) 118 cm3
(b) 200 cm3
(c) 236 cm3
(d) 400 cm3
Final answer:
OPTION A.
Using Charles's Law, the temperature of the balloon is converted to Kelvin and the law is applied to find the new volume when the temperature is increased from 60°C to 120°C. The new volume is approximately 118 cm³.
Explanation:
The question involves applying Charles's Law, which states that the volume of a gas is directly proportional to its temperature when pressure is constant. To find the new volume after an increase in temperature, we convert the temperatures from Celsius to Kelvin by adding 273. The initial temperature (T1) is thus 60°C + 273 = 333K and the final temperature (T2) is 120°C + 273 = 393K. The initial volume (V1) is 100 cm³.
Charles's Law is given by the formula V1/T1 = V2/T2, where V2 is the final volume. Applying this formula, we get:
V1/T1 = V2/T2
(100 cm³) / (333K) = V2 / (393K)
Multiplying both sides by 393K, we find the final volume V2:
V2 = (100 cm³) * (393K) / (333K)
This results in:
V2 ≈ 118 cm³
Therefore, the new volume of the balloon, after increasing the temperature from 60°C to 120°C, will be approximately 118 cm³.
What change will be caused by addition of a small amount of hcl to a solution containing fluoride ions and hydrogen fluoride?
Answer:
The addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride will cause the equilibrium shift to the production of more hydrogen fluoride.Explanation:
The solution containing fluoride ions and hydrogen fluoride (a weak acid) may be chemically represented by this equilibrium equation:
F⁻ (aq) + H⁺ (aq) ⇄ HF (aq)The HCl, a strong acid, added will ionize in water according to this chemical equation:
HCl (aq) → H⁺ (aq) + Cl⁻ (aq)Then, following Le Chatelir's principle, the addtion of H⁺ ions coming from the HCl dissociation, will increase the concentration of H⁺ in the solution, driving to the consumption of some F⁻ ions, and the production of more HF acid. This is a shift of the equilbrium toward the HF side.
Adding hydrochloric acid to a solution of fluoride ions and hydrogen fluoride will decrease the pH and increase the concentration of hydrofluoric acid while decreasing the concentration of fluoride ions.
When hydrochloric acid (HCl) is added to a solution containing fluoride ions and hydrogen fluoride, it will cause a decrease in the pH of the solution. This is because HCl is a strong acid and it will dissociate completely in water to release hydronium ions (H3O+), resulting in an increase in the solution's acidity. Furthermore, according to Le Chatelier's principle, the addition of HCl will push the equilibrium of the reaction:
HF(aq) + H2O(l) ⇌ H3O+(aq) + F¯(aq)
to the left, meaning that the concentration of hydrofluoric acid (HF) will increase, while the concentration of fluoride ions (F−) will decrease, due to the additional supply of common ions from HCl.
What is the Ka of 0.168M solution of Hydrocyanic acid (HCN) with pH of 3.15?
The answer is in the photo, but a 0,168 M HCN doesn’t have a pH of 3,15, but 5. HCN real Ka is 6,17*10^(-10).
Answer:
The real answer is 3.00x10^-6
Explanation:
Fill in 3.00 and then -6
A sample of which radioisotope emits particles havingthe greatest mass? A) 137Cs B) 53Fe C) 220Fr D) 3H
Answer:
c) 220 Fr
Explanation:
castle learning
The radioisotope which emits particles having the greatest mass will be 220Fr.
What is radioisotope?The radioactive isotopes of just an element are known as radioisotopes. Atoms with an unbalanced mixture of neutrons as well as protons, with extra energy in their nucleus, are also known as neutron-proton atoms.
What is massThe quantity of matter in a thing is measured by its mass.
When only the 3 most prevalent forms of ionizing radiation are considered, alpha particles get the most mass. The mass of an alpha particle is four times that of a proton as well a neutron, as well as the weight of a beta particle, is roughly 8,000 times that of a proton or neutron.
Therefore, 220 Fr will be having the greatest mass.
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Hydrazine (N2H4), a rocket fuel , reacts with oxygen to form nitrogen gas and water vapor. The reaction is represented with the equation:
N2H4(l) + O2(g) → N2(g) + 2H2O(g)
At STP, if 4.20L of O2 reacts with N2H4, how many liters of water vapor will be produced?
A)
2.10L H2O(g)
B)
2.67L H2O(g)
C)
5.33L H2O(g)
D)
8.40L H2O(g)
Answer:
D) 8.40 L H₂O(g).
Explanation:
The balanced equation for the mentioned reaction is:2N₂H₄(l) + O₂(g) → N₂(g) + 2H₂O(g),
It is clear that 2.0 moles of N₂H₄ react with 1.0 mole of O₂ to produce 2.0 moles of N₂ and 2.0 moles of H₂O.
At STP, 4.20L of O₂ reacts with N₂H₄:
It is known that at STP: every 1.0 mol of any gas occupies 22.4 L.
using cross multiplication:
1.0 mol of O₂ represents → 22.4 L.
??? mol of O₂ represents → 4.2 L.
∴ 4.2 L of O₂ represents = (1.0 mol)(4.2 L)/(22.4 L) = 0.1875 mol.
To find the no. of moles of H₂O produced:Using cross multiplication:
1.0 mol of O₂ produce → 2.0 mol of H₂O, from stichiometry.
0.1875 mol of O₂ produce → ??? mol of H₂O.
∴ The no. of moles of H₂O = (2.0 mol)(0.1875 mol)/(1.0 mol) = 3.75 mol.
Again, using cross multiplication:1.0 mol of H₂O represents → 22.4 L, at STP.
3.75 mol of H₂O represents → ??? L.
∴ The no. of liters of water vapor will be produced = (3.75 mol)(22.4 L)/(1.0 mol) = 8.4 L.
So, the right choice is: D) 8.40 L H₂O(g).
Final answer:
Using the balanced chemical equation, stoichiometry, and Avogadro's law, we determine that if 4.20 liters of O₂ reacts, it will produce 8.40 liters of H₂O vapor. The correct answer is 8.40L of H₂O vapor.
Explanation:
The question involves a stoichiometric calculation based on the balanced chemical equation for the reaction between hydrazine (N₂H₄) and oxygen (O₂) to produce nitrogen gas (N₂) and water vapor (H₂O). At STP (standard temperature and pressure), one mole of any gas occupies 22.4 liters. According to the balanced chemical equation:
N₂H₄(l) + O₂(g) ⇒N₂(g) + 2H₂O(g)
We can see that 1 mole of O₂ reacts with 1 mole of N₂H₄ to produce 2 moles of H₂O. If 4.20 liters of O₂ are reacted, we can use Avogadro's law to determine the volume of H₂O produced, which will be twice the volume of O₂ reacted because of the 1:2 molar ratio. Therefore, the volume of water vapor produced will be:
4.20 L O₂(g) x (2 moles H₂O / 1 mole O₂) = 8.40 L H₂O(g)
The correct answer is 8.40 L H₂O(g), which corresponds to option D.
What is the oxidation number of Mn in MnO2?
2
3
4
1
Mn’s oxidation number is +4 because the overall compound is neutral/has a 0 charge. So since O always has a -2 oxidation number except in special cases (ex: H2O2) and since oxidation numbers add up to the compound’s charge, x + -2(2) = 0 which means x = 4. thus the oxidation number is 4.
Final answer:
The oxidation number of Mn in MnO2 is +4. This is determined by balancing the total negative charge of -4 from the two oxygen atoms with the positive charge from manganese which must balance to zero in a neutral compound.
Explanation:
The oxidation number of Mn in MnO2 is +4. When determining oxidation numbers, remember that the sum of oxidation numbers in a neutral compound must equal zero. Since each oxygen atom has an oxidation number of -2, and there are two oxygen atoms totaling -4, manganese must have an oxidation number of +4 to balance the charge.
MnO2 is manganese(IV) oxide, indicating that manganese is in the +4 oxidation state. The formula reflects that there are four total electrons that have been transferred to oxygen atoms in this compound, making it less paramagnetic than when manganese is in the +3 state, as seen in manganese(III) oxide, Mn2O3.
Which equation shows how to calculate how many grams (g) of Mg(OH)2 would be produced from 4mol KOH? The balanced reaction is:
MgCl2(small 2) + 2KOH -----> Mg(OH)2(small2) + 2KCL
Answer:
4 mol of KOH would produce 116.6 g of Mg(OH)₂
Explanation:
According to the following balanced equation:
MgCl₂+ 2 KOH -----> Mg(OH)₂ + 2 KCLOne can note that 2 mol of KOH react with MgCl₂ to produce 1 mol of Mg(OH)₂.
using cross multiplication
2 mol of KOH → 1 mol of Mg(OH)₂.
4 mol of KOH → ?? mol of Mg(OH)₂.
no of moles of Mg(OH)₂ = (1 mol* 4 mol) / 2 mol =2 mol
Now we can convert moles of Mg(OH)₂ to grams using the formula
mass of Mg(OH)₂= (no. of moles * molar mass) = (2 mol * 58.3g/mol) = 116.6 g
So, 4 mol of KOH would produce 116.6 g of Mg(OH)₂.What volume of a 2.0M NaOH solution would be lethal for a 60kg person?
(LD50 NaOH = 0.0010 mol/kg)
Answer:
[tex]\boxed{\text{30 mL}}[/tex]
Explanation:
Step 1. Calculate the moles of NaOH
[tex]n = \text{60.0 kg} \times \dfrac{\text{0.0010 mol}}{\text{1 kg}} = \text{0.0600 mol}[/tex]
Step 2. Calculate the volume of NaOH
[tex]V = \text{0.0600 mol} \times \dfrac{\text{1 L}}{\text{2.0 mol}} = \text{0.030 L} = \text{30 mL}\\\\\text{The lethal volume of NaOH is } \boxed{\textbf{30 mL}}[/tex]
Final answer:
To find the lethal volume of a 2.0M NaOH solution for a 60kg person, calculate the total lethal dose (0.060 mol) and then divide by the concentration (2.0M), resulting in 30 mL.
Explanation:
The question involves calculating the lethal volume of a 2.0M NaOH solution for a 60kg person based on the lethal dose (LD50) of NaOH, which is 0.0010 mol/kg. First, we need to determine the total lethal dose of NaOH for the person:
Total lethal dose = LD50 * Body weight = 0.0010 mol/kg * 60 kg = 0.060 mol.To find the volume of the 2.0M NaOH solution needed to reach this lethal dose, we use the formula: Volume = moles of solute/concentration of solution.Volume = 0.060 mol / 2.0 M = 0.030 L or 30 mL.Therefore, the lethal volume of a 2.0M NaOH solution for a 60kg person is 30 mL.
Why is water considered the universal solvent
Because of its high solubility, water is considered to be a universal solvent.
What is a universal solvent?
A substance that displaces most compounds is known as a universal solvent. Because it dissolves more chemicals than any other solvent, water is known as the universal solvent. But no solvent, not even water, can dissolve all chemicals. According to the principle of "like dissolves like," polar solvents typically dissolve polar compounds, such as salts.
Nonpolar solvents may dissolve organic molecules like lipids and other nonpolar substances. Because of its polar nature, which gives each molecule a hydrophobic (water-fearing) and hydrophilic (water-loving) side, water dissolves more compounds than any other solvent.
The oxygen atom has a tiny negative electrical charge, whereas the side of the molecules with two hydrogen atoms carries a slight positive electrical charge. Water's polarisation makes it possible for it to draw in a wide variety of molecules. Water is able to split the substance into its ions due to the strong attraction to ionic molecules like sodium chloride or salt.
Therefore, water is considered a universal solvent.
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Ammonium carbonate and iron(iii) nitrate are combined, solid iron(iii) carbonate and a solution of ammonium nitrate are formed. the net ionic equation for this reaction is:
Answer:
The net ionic equation is: 3CO₃²⁻(aq) + 2Fe³⁺(aq) → Fe₂(CO₃)₃(s).
Explanation:
For the mentioned reaction:We have the Molecular reaction:3(NH₄)₂CO₃(aq) + 2Fe(NO₃)₃(aq) → Fe₂(CO₃)₃(s) + 6NH₄NO₃(aq)
We have the total ionic reaction:
6NH₄⁺(aq) + 3CO₃²⁻(aq) + 2Fe³⁺(aq) + 6NO₃⁻ → Fe₂(CO₃)₃(s) + 6NH₄⁺(aq) + 6NO₃⁻(aq).
NH₄⁺(aq) and NO₃⁻(aq) are spectator ions that are not changed through the reaction and still dissolved in the medium, so they can be omitted to get the net ionic equation.
So, the net ionic equation is:
3CO₃²⁻(aq) + 2Fe³⁺(aq) → Fe₂(CO₃)₃(s).
Final answer:
The reaction between ammonium carbonate and iron(III) nitrate forms solid iron(III) carbonate and a solution of ammonium nitrate. The net ionic equation for this precipitation reaction is CO3^2-(aq) + Fe^3+(aq) → Fe2(CO3)3(s), which indicates the formation of the insoluble iron(III) carbonate.
Explanation:
When ammonium carbonate is combined with iron(III) nitrate, a reaction occurs where a solid precipitate and a solution of another compound are formed. According to the solubility rules, certain combinations of reactants will lead to the formation of an insoluble product, known as a precipitate. In this case, iron(III) carbonate is the precipitate, and ammonium nitrate remains in the solution.
To write the net ionic equation for this reaction, we must first write the balanced molecular equation and then the complete ionic equation. We can then identify and remove the spectator ions, which are ions that appear on both sides of the equation without undergoing a chemical change, to finally derive the net ionic equation.
The molecular equation is:
(NH4)2CO3(aq) + Fe(NO3)3(aq) → Fe2(CO3)3(s) + 3NH4NO3(aq)
The complete ionic equation is:
2NH4+(aq) + CO32-(aq) + Fe3+(aq) + 3NO3-(aq) → Fe2(CO3)3(s) + 3NH4+(aq) + 3NO3-(aq)
After identifying that the ammonium (NH4+) and nitrate (NO3-) ions are spectator ions, they can be eliminated from the equation, resulting in the net ionic equation:
CO32-(aq) + Fe3+(aq) → Fe2(CO3)3(s)
This net ionic equation represents the formation of the insoluble iron(III) carbonate precipitate from the aqueous reactants.
What is the balanced equation for the combustion of sulfur
Answer:
There are three possible chemical equations for the combustion of sulfur:
2S (s) + O₂ (g) → 2SO (g)S (s) + O₂ (g) → SO₂ (g)2S (s) + 3O₂ (g) → 2SO₃ (g)Explanation:
Combustion is a reaction with oxygen. The products of the reaction are oxides, and energy is released in the form of heat and light.
Sulfur iis a nonmetal, so the oxide formed is a nonmetal oxide.
The most common oxidation numbers of sulfur are -2, + 2, + 4, and + 6.
The combination of sulfur with oxygen may be only with the positive oxidation numbers (+2, + 4, and +6).
Then you have three different equations for sulfur combustion:
1) Oxidation number +2:
S(s) + O₂(g) → SO(g)Which when balanced is: 2S(g) + O₂(g) → 2SO(g)
2) Oxitation number +4:
S(s) + O₂(g) → SO₂(g)That equation is already balanced.
3) Oxidation number +6:
S(s) + O₂(g) → SO₃(g)Which when balanced is: 2S(s) + 3O₂(g) → 2SO₃(g)
The balanced equation for the combustion of sulfur is [tex]\[ \text{S}(s) + \text{O}_2(g) \rightarrow \text{SO}_2(g) \][/tex]
To balance this equation, we need to ensure that the number of atoms of each element is the same on both sides of the equation. Sulfur (S) is present as a diatomic molecule [tex](S_2)[/tex] when it reacts with oxygen [tex](O_2)[/tex] to form sulfur dioxide [tex](SO_2)[/tex]. The balanced equation considering the diatomic nature of sulfur is:
[tex]\[ \text{S}_2(s) + \text{O}_2(g) \rightarrow 2\text{SO}_2(g) \][/tex]
Here's the step-by-step process to balance the equation:
1. Start by writing the unbalanced equation with the correct formulas for the reactants and products:
[tex]\[ \text{S}_2 + \text{O}_2 \rightarrow \text{SO}_2 \][/tex]
2. Count the number of atoms of each element on both sides of the equation:
On the left side, there are 2 sulfur (S) atoms and 2 oxygen (O) atoms.
On the right side, there is 1 sulfur (S) atom and 2 oxygen (O) atoms.
3. To balance the sulfur atoms, we need to have the same number of sulfur atoms on both sides. Since there are 2 sulfur atoms on the left, we need to multiply the sulfur dioxide [tex](SO_2)[/tex] by 2 on the right side:
[tex]\[ \text{S}_2 + \text{O}_2 \rightarrow 2\text{SO}_2 \][/tex]
4. Now, count the number of oxygen atoms again. There are 2 oxygen atoms on the left and 4 on the right (2 molecules of [tex]SO_2[/tex], each with 2 oxygen atoms).
5. To balance the oxygen atoms, we need to have 4 oxygen atoms on the left side as well. Since we already have 2 oxygen atoms in one [tex]O_2[/tex] molecule, we need to add another [tex]O_2[/tex] molecule:
[tex]\[ \text{S}_2 + 2\text{O}_2 \rightarrow 2\text{SO}_2 \][/tex]
6. Finally, count the atoms on both sides to confirm that the equation is balanced:
Left side: 2 S atoms and 4 O atoms.
Right side: 2 S atoms (2 molecules of [tex]SO_2[/tex], each with 1 S atom) and 4 O atoms (2 molecules of [tex]SO_2[/tex], each with 2 O atoms).
The equation is now balanced with 2 sulfur atoms and 4 oxygen atoms on both sides."
A container holds a pure sample of a radioactive substance with a half-life of 2 hours. Which of the following statements are true?
a) After 1 hour, less than 50 % of the original atoms in the container will have decayed.
b) After 1 hour, more than 50 % of the original atoms in the container will have decayed.
c) After 2 hours, 50 % of the original atoms in the container will have decayed.
d) After 4 hours, 25 % of the original atoms will have decayed.
e) After 4 hours, the total number of atoms in the container will be reduced by 75 %.
A container holds a pure sample of a radioactive substance with a half-life of 2 hours. The true statements are a, c and d.
a) After 1 hour, less than 50 % of the original atoms in the container will have decayed.
True. The half-life of the radioactive substance is 2 hours, which means that after 1 hour, only half of the original atoms would have decayed. Therefore, less than 50% of the original atoms will have decayed.
b) After 1 hour, more than 50 % of the original atoms in the container will have decayed.
False. As explained in statement (a), after 1 hour, less than 50% of the original atoms will have decayed, not more than 50%.
c) After 2 hours, 50 % of the original atoms in the container will have decayed.
True. The half-life of the radioactive substance is 2 hours, so after 2 hours, exactly 50% of the original atoms will have decayed.
d) After 4 hours, 25 % of the original atoms will have decayed.
True. Since the half-life is 2 hours, after 4 hours (2 half-lives), 50% of the original atoms will have decayed. Therefore, 25% of the original atoms will remain after 4 hours.
e) After 4 hours, the total number of atoms in the container will be reduced by 75 %.
False. After 4 hours, as explained in statement (d), 25% of the original atoms will remain, not 75%. So, the total number of atoms will be reduced by 100% - 25% = 75%, not 75%.
Correct statements: a), c), and d).
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A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper; the aluminum and the copper are in thermal contact. The specific heat of aluminum is more than double that of copper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium?
Answer:
Copper is the object that experiences the greater temperature change.Explanation:
Thermally isolated system means that the system does not exchange thermal energy with the surroundings.
Hence, any thermal exchange, in virtue of the temperature difference of the aluminum and copper pieces, is between them.
In consequence, the law of conservation of energy states that the heat lost by the hot substance will be gained by the cold matter.
In equations, that is:
Heat lost by aluminum = heat gained by copper.Now, the gain or loss or heat of a substance, Q, is related with the mass (m), the specific heat (Cs), and the cahnge of temperature (ΔT), per the equation:
Q = m × Cs × ΔT∴ Q lost by aluminum = Q gained copper ⇒
[m × Cs × ΔT ] aluminum = [m × Cs × ΔT ] copper.Under the reasoning assumption that the masses of aluminum and copper are equal, the equations is simplified to:
[Cs × ΔT ] aluminum = [Cs × ΔT ] copper.Cs aluminum / Cs copper = ΔT copper / ΔT aluminumCs aluminum > 2 × Cs copper ⇒ Cs Cs aluminum / Cs copper > 2 ΔT copper / ΔT aluminumΔT copper / ΔT aluminum > 2 ΔT copper > 2 × ΔT aluminumIn words, since it is stated that the specific heat of aluminum is more than double that of copper, in order to keep the equality, ΔT of copper shall be more than double ΔT of aluminum.
Hence, the conclusion is that the object that experiences the greater temperature change is copper (the one with the lower specific heat), under the assumption that both objects have the same amount of matter (mass).
In the thermally isolated system, the copper experiences a greater temperature change than the aluminum because copper has a lower specific heat. It means that copper requires less energy to change its temperature compared to aluminum.
Explanation:In a thermally isolated system like the one you've asked about, energy isn't gained or lost, but it does transfer among parts of the system until all parts are at the same temperature, which we call thermal equilibrium. Given that copper has a lower specific heat than aluminum, the same amount of heat transfer will cause a larger temperature change in the copper. This is due to the way specific heat works: substances with higher specific heat require more energy to change their temperature, while those with lower specific heat require less.
It's like running a race: if the specific heat is the distance of the race, the runner (or heat energy) with a shorter race (lower specific heat) will finish (change temperature) more quickly than a runner with a longer race (higher specific heat).
How Specific Heat Affects Temperature ChangeSpecific heat is the amount of heat per unit mass required to raise the temperature of a substance by one degree Celsius. In this case, the aluminum, with a higher specific heat, would need more energy (heat) to alter its temperature. Since the energy is transferred from the aluminum (hot) to the copper (cold), the copper, with a lower specific heat, experiences more temperature change until thermal equilibrium is reached.
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Plastic is made from ____. a leachates produced by bioenzymes b melted silica sand grains c byproducts of coal mining d extraction of inorganic solids oil and natural gas e organic molecules derived from oil and natural gas
Answer:
plastic is made from polymers.
Why does increasing temperature increase the rate of reaction?
Answer:
Explanation:
Reaction rate measures the speed of chemical reaction and how they proceed with time.
The theories that have been propounded about reactions rates shows that increasing temperature is very important in chemical reactions.
From observation, chemical reaction rates are controlled by:
Nature of the reactantsConcentration of the reactants or pressure for gasesTemperaturePresence of catalystSunlightIncreasing temperature temperature releases heat energy to drive reactions into completing faster. Collisions between reacting particles becomes more as a result of increase in energy. This energy when greater than the activation energy of the reaction would further influence the effectiveness of collisions between reacting particles. This would therefore make reactions proceed faster with more increase in temperature.
Use the changes in oxidation numbers to identify which atom is oxidized, reduced, the oxidizing agent, and the reducing agent. 5
A
2H2(g) + O2(g) → 2H2O(l)
B
2KNO3(s) → 2KNO2(s) + O2(g)
Answer:
Reaction A:
Hydrogen atoms in H₂ are oxidized.Oxygen atoms in O₂ are reduced.Hydrogen gas H₂ is the reducing agent.Oxygen gas O₂ is the oxidizing agent.Reaction B:
Oxygen atoms in KNO₃ are oxidized.Nitrogen atoms in KNO₃ are reduced.Potassium nitrate (V) KNO₃ is both the oxidizing agent and the reducing agent.Explanation:
When an atom is oxidized, its oxidation number increases.When an atom is reduced, its oxidation number decreases.The oxidizing agent contains atoms that are reduced.The reducing agent contains atoms that are oxidized.Here are some common rules for assigning oxidation states.
Oxidation states on all atoms in a neutral compound shall add up to 0.The average oxidation state on an atom is zero if the compound contains only atoms of that element. (E.g., the oxidation state on O in O₂ is zero.)The oxidation state on oxygen atoms in compounds is typically -2. (Exceptions: oxygen bonded to fluorine, and peroxides.)The oxidation state on group one metals (Li, Na, K) in compounds is typically +1. The oxidation state on group two metals (Mg, Ca, Ba) in compounds is typically +2.The oxidation state on H in compounds is typically +1. (Exceptions: metal hydrides where the oxidation state on H can be -1.)For this question, only the rule about neutral compounds, oxygen, and group one metals (K in this case) are needed.
Reaction BOxidation states in KNO₃:
K is a group one metal. The oxidation state on K in the compound KNO₃ shall be +1.The oxidation state on N tend to vary a lot, from -3 all the way to +5. Leave that as [tex]x[/tex] for now.There's no fluorine in KNO₃. The ion NO₃⁻ stands for nitrate. There's no peroxide in that ion. The oxidation state on O in this compound shall be -2.Let the oxidation state on N be [tex]x[/tex]. The oxidation state of all five atoms in the formula KNO₃ shall add up to zero. [tex]1\times (+1) + 1 \times (x) + {\bf 3} \times (-2) = 0\\x = +5[/tex]. As a result, the oxidation state on N in KNO₃ will be +5.Similarly, for KNO₂:
The oxidation state on the group one metal K in KNO₂ will still be +1.Let the oxidation state on N be [tex]y[/tex].There's no peroxide in the nitrite ion, NO₂⁻, either. The oxidation state on O in KNO₂ will still be -2.The oxidation state on all atoms in this formula shall add up to 0. Solve for the oxidation state on N: [tex]1\times (+1) + 1 \times (y) + {\bf 2}\times (-2) = 0\\y = +3[/tex]. The oxidation state on N in KNO₂ will be +3.Oxygen is the only element in O₂. As a result,
The oxidation state on O in O₂ will be 0.[tex]\rm\stackrel{+1}{K}\stackrel{\bf +5}{N}\stackrel{\bf -2}{O}_3 \to \stackrel{+1}{K}\stackrel{\bf+3}{N}\stackrel{\bf -2}{O}_2 + \stackrel{\bf 0}{O}_2[/tex].
The oxidation state on two oxygen atoms in KNO₃ increases from -2 to 0. These oxygen atoms are oxidized. KNO₃ is also the reducing agent.
The oxidation state on the nitrogen atom in KNO₃ decreases from +5 to +3. That nitrogen atom is reduced. As a result, KNO₃ is also the oxidizing agent.
Reaction A
Apply these steps to reaction A.
H₂:
Oxidation state on H: 0.O₂:
Oxidation state on O: 0.H₂O:
Oxidation state on H: +1.Oxidation state on O: -2.Double check: [tex]{\bf 2} \times (+1) + (-2) = 0[/tex].[tex]\rm \stackrel{}{2}\; \stackrel{\bf 0}{H}_2 + \stackrel{\bf 0}{O}_2\stackrel{}{\to} \stackrel{}{2}\;\stackrel{\bf +1}{H}_2\stackrel{\bf -2}{O}[/tex].
The oxidation state on oxygen atoms decreases from 0 to -2. Those oxygen atoms are reduced. O₂ is thus the oxidizing agent.
The oxidation state on hydrogen atoms increases from 0 to +1. Those hydrogen atoms are oxidized. H₂ is thus the reducing agent.
In the reaction 2H₂(g) + O₂(g) → 2H₂O(l), hydrogen is oxidized and acts as the reducing agent, while oxygen is reduced and acts as the oxidizing agent. Option A is correct.
To identify which species is oxidized and which is reduced in the given reaction 2H₂(g) + O₂(g) → 2H₂O(l), we start by assigning oxidation numbers. Hydrogen is usually +1 (except in metal hydrides, where it is -1), and oxygen is usually -2 (except in peroxides, where it is -1, and in compounds with fluorine, where it is positive). In molecular hydrogen (H₂) and molecular oxygen (O₂), the oxidation numbers are 0 since they are elemental forms.
In water (H₂O), hydrogen has an oxidation number of +1 and oxygen has an oxidation number of -2. Going from 0 in H₂ to +1 in H₂O, hydrogen is oxidized (loses electrons), and going from 0 in O₂ to -2 in H₂O, oxygen is reduced (gains electrons).
Therefore, hydrogen is the reducing agent (it itself gets oxidized), and oxygen is the oxidizing agent (it itself gets reduced).
Hence, A. is the correct option.
What is the process that changes one set of chemicals into another set of chemicals
Answer:
A chemical reaction is a process that changes one set of chemicals into another set of chemicals. The elements or compounds that enter into the reaction are the ► reactants. The elements or compounds produced by the reaction are the ► products.
What is meant by the half-life of a radioactive substance
Answer:
Explanation:
The half life of a radioactive atom is the time taken for half of the radioactive nuclei to disintegrate. The shorter the half life, the faster a radioactive nuclei decays.
Half life is often expressed as:
Half life = [tex]\frac{0.693}{λ}[/tex]
Where λ is the decay constant.
In the lab, a chemist adds 3.6 grams of sodium chloride to 100.0 g of water. what is the molality of the solution?
Answer:
0.616 m.
Explanation:
Molality (m) is defined as the no. of moles of solute dissolved in a 1.0 kg of the solvent.m = (no. of moles of solute)/(mass of the solvent (kg))
m = (mass/molar mass) NaCl / (mass of the solvent (kg))
mass of NaCl = 3.6 g, molar mass of NaCl = 58.44 g/mol, mass of water = 100.0 g = 0.1 kg.
m = (mass/molar mass) NaCl / (mass of the solvent (kg)) = (3.6 g / 58.44 g/mol) / (0.1 kg) = 0.616 m.
The molality of a solution if a chemist adds 3.6 grams of sodium chloride to 100.0 g of water is 0.615m.
What is molality?Molality is defined as the no. of moles of solute dissolved in a 1.0 kg of the solvent.
m = no. of moles of solute ÷ mass of the solvent (kg)
no of moles of NaCl = 3.6g ÷ 58.5g/mol = 0.0615mol
Molality = 0.0615mol ÷ 0.1kg
Molality = 0.615m
Therefore, the molality of a solution if a chemist adds 3.6 grams of sodium chloride to 100.0 g of water is 0.615m.
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How many moles of aluminum are needed to react completely with 1.2 mol of feo
Answer:
0.8 mol.
Explanation:
The balanced equation for the reaction between Al and FeO is represented as:2Al + 3FeO → 3Fe + Al₂O₃,
It is clear that 2 mol of Al react with 3 mol of FeO to produce 3 mol of Fe and 1 mol of Al₂O₃.
Using cross multiplication:
2 mol of Al needs → 3 mol of FeO, from stichiometry.
??? mol of Al needs → 1.2 mol of FeO.
∴ The no. of moles of Al are needed to react completely with 1.2 mol of FeO = (2 mol)(1.2 mol)/(3 mol) = 0.8 mol.
Considering the reaction stoichiometry, 0.8 moles of aluminum are needed to react completely with 1.2 moles of FeO.
The balanced reaction is:
2 Al + 3 FeO → 3 Fe + Al₂O₃
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
Al: 2 moles FeO: 3 moles Fe: 3 moles Al₂O₃: 1 moleThen you can apply the following rule of three: if by stoichiometry 3 moles of FeO react with 2 moles of Al, 1.2 moles of FeO react with how many moles of Al?
[tex]amount of moles of Al= \frac{1.2 moles of FeOx2 moles of Al}{3 moles of FeO}[/tex]
amount of moles of Al= 0.8 moles
Finally, 0.8 moles of aluminum are needed to react completely with 1.2 moles of FeO.
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Assuming equal concentrations and complete dissociation, rank these aqueous solutions by their freezing points.
Li_2SO_4 NH_4l CoCl_3
Highest freezing point Lowest freezing point
Answer:
CoCl₃ > Li₂SO₄ > NH₄I.
Explanation:
Adding solute to water causes depression of the boiling point.The depression in freezing point (ΔTf) can be calculated using the relation:ΔTf = i.Kf.m,
where, ΔTf is the depression in freezing point.
i is the van 't Hoff factor.
van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.Kf is the molal depression constant of water.
m is the molality of the solution.
(1) Li₂SO₄:
i for Li₂SO₄ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.
∴ ΔTb for (Li₂SO₄) = i.Kb.m = (3)(Kf)(m) = 3(Kf)(m).
(2) NH₄I:
i for NH₄I = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.
∴ ΔTb for (NH₄I) = i.Kb.m = (2)(Kf)(m) = 2(Kf)(m).
(3) CoCl₃:
i for CoCl₃ = no. of particles produced when the substance is dissolved/no. of original particle = 4/1 = 4.
∴ ΔTb for (CoCl₃) = i.Kb.m = (4)(Kf)(m) = 4(Kf)(m).
So, the ranking of the freezing point from the highest to the lowest is:CoCl₃ > Li₂SO₄ > NH₄I.
Final answer:
The aqueous solutions ranked from highest to lowest freezing point, based on the number of ions they produce upon dissociation, is NH4I (highest freezing point), followed by Li2SO4, and then CoCl3 (lowest freezing point).
Explanation:
To rank aqueous solutions by their freezing points when they have equal concentrations and are completely dissociated, we look at the number of ions each compound dissociates into when dissolved. The more ions produced, the lower the freezing point of the solution due to a greater freezing point depression effect. The given solutions are Li2SO4, NH4I, and CoCl3. Li2SO4 dissociates into 3 ions (2 Li+ + SO42-), NH4I dissociates into 2 ions (NH4+ + I-), and CoCl3 dissociates into 4 ions (Co3+ + 3 Cl-). Therefore, the order from highest to lowest freezing point is: NH4I > Li2SO4 > CoCl3.