Mendeleev organized the periodic table based on atomic mass and chemical properties, deviating from mass order to group chemically similar elements, which allowed him to predict undiscovered elements.
Dmitri Mendeleev did not order the periodic table by equal rows and columns because, during his arrangement of the elements based on their atomic mass, he discovered that placing elements strictly by mass did not result in a table where elements with similar chemical properties were grouped together. Instead, he noticed a pattern of periodicity, where elements showed repeating properties at certain intervals. To maintain this periodicity and to properly organize elements into groups of similar chemical behaviors, he deviated from strict mass order.
For example, he placed iodine after tellurium despite it being lighter, to align it with chemically similar elements. This arrangement also allowed Mendeleev to predict the existence and properties of elements that were undiscovered at the time, based on the gaps and trends in his table. The columns of Mendeleev's periodic table represent groups and the rows represent periods, each row being more massive than the one above it.
Organic Chemistry, 7e by L. G. Wade, Jr. Reactions of Alkenes Christine Hermann Radford University Radford VA Copyright © 2010 Pearson Education
Answer: Christine Herman & L.G Wade Jr., "2010". Organic Chemistry: Reaction of Alkane, 7e, Pearson Education, Radford University, Radford, VA.
Explanation:
This is an edited book. The Harvard reference style was used in the following order:
Authors name
Year of publication
Title
Edition
Publisher
Place of publication.
Note that the title of book should be italicized with capitalization of first word.
10.0 mL of a Cu2+ solution of unknown concentration was placed in a 250 mL Erlenmeyer flask. An excess of KI solution was added. Indicator was added and the solution was diluted with H2O to a total volume of 75 mL. For rxn 2, the solution from rxn 1 was titrated with 0.15 M Na2S2O3. The equivalence point of the titration was reached when 13.05 mL of Na2S2O3 had been added. What is the molar concentration of Cu2+ in the original 10.0 mL solution?
Answer:
Molar concentration: 0,0489M
Explanation:
In this titration of Cu²⁺ you add an excess of I⁻ that reacts with Cu²⁺ producing I₂, this I₂ reacts with Na₂S₂O₃. If you know the I₂ that reacts with Na₂S₂O₃ you can know the I⁻ that reacts with Cu²⁺ and, thus, the quantity of Cu²⁺. The reactions are:
2Cu²⁺ + 4I⁻ → 2CuI + I₂
I₂ + 2S₂O₃⁻ → S₄O₆ + 2I⁻
Moles of S₂O₃⁻ are:
0,01305L×0,15M = 1,96x10⁻³ moles of S₂O₃⁻.
Moles of I₂ are:
1,96x10⁻³ moles of S₂O₃⁻× ( 1 mole of I₂ / 2 moles of S₂O₃⁻) = 9,79x10⁻⁴ moles of I₂
Moles of Cu²⁺ are:
9,79x10⁻⁴ moles of I₂×( 2 moles of Cu²⁺ / 4 moles of I₂) = 4,89x10⁻⁴ moles of Cu²⁺
As volume of the solution was 10,0mL = 0,0100L, the molar concentration of the original solution is:
4,89x10⁻⁴ moles of Cu²⁺ / 0,0100L = 0,0489M
The unknown concentration of the Cu2+ solution can be found by determining the moles of Na2S2O3 at the equivalence point, using this to calculate the moles of Cu2+ from stoichiometry, and then dividing by the volume of the Cu2+ solution in liters.
Explanation:In this question, a Cu2+ solution, of unknown concentration, is titrated with 0.15 M Na2S2O3. The Cu2+ solution's concentration can be calculated using the data provided. The titration of this Cu2+ solution is complete, or the equivalence point is reached, when 13.05 mL of Na2S2O3 is added. The reaction that occurs is 2Na2S2O3 + Cu2+ -> CuS2O3 + 2Na+, and from the stoichiometry of the reaction, we know that two moles of Na2S2O3 react with one mole of Cu2+ ion.
Using the moles of Na2S2O3 that reacted (moles = Molarity x Volume (in liters), so moles = 0.15 M x 13.05 mL/1000), we can find out the moles of Cu2+ that were present in the 10 mL sample. We can then calculate the molarity of the Cu2+ solution by dividing the moles of Cu2+ by the volume of the solution in liters (0.01 L).
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if all of the carbon atoms are linked by single covalent bonds and there are no branches, the compounds are called_____________.
Answer: If all of the carbon atoms are linked by single covalent bonds and there are no branches, the compounds are called homologous series.
Explanation:
A series of carbon atoms which include different number of carbon atoms but have same functional group are known as homologous series.
Generally, these type of series have a chemical formula as [tex]C_{n}H_{2n+2}[/tex].
No branches are present in this type of series.
For example, [tex]CH_{4}[/tex], [tex]C_{2}H_{6}[/tex], [tex]C_{3}H_{8}[/tex] etc are all homologous series.
Thus, we can conclude that if all of the carbon atoms are linked by single covalent bonds and there are no branches, the compounds are called homologous series.
Analyze feasibility of given reactions based on electrode potentials at standard conditions and nonstandard conditions.
Answer and Explanation:
In order to predict the feasibility of redox processes, standard electrode potentials are majorly employed. Generally, if the electrode potential for the reaction is positive, it is considered to be feasible. However, some conditions affect this statement
The value of E° talks about the feasibility of the reaction under standard conditions only and says nothing about the reaction rate.
A positive value of E° means, the equilibrium constant K is greater than 1; while a negative value of E° means, that it is less than 1.
The attachment below shows the simple analysis of the feasibility of two different reactions A and B, at standard and non standard conditions respectively.
NOTE: Standard conditions for Redox reaction: 298.15K(Temperature), 1 atm(Pressure), 1.0M(Concentration) for both anode and cathode.
Non standard conditions for Redox reaction: Any of the 3 conditions above are changed, especially the concentration.
Over 200 items are scored on the driving test. You may only make ______ or fewer errors to pass the test.
Answer:
The correct answer is 15.
Explanation:
The driving test must be passed with more than 200 points. This means that you can only make a maximum of 15 mistakes to pass the test. This is possible as long as no critical mistakes are made, which are enough to fail the test. These critical mistakes are for example driving faster than allowed, too slow, driving distracted, etc.
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capable of bonding to surfaces with the application of light pressure is a chemical or physical reaction?
Answer:
Capable of bonding to surfaces with the application of light pressure is a chemical reaction.
Explanation:
Here, bonding occurs . Bonding results in destruction of old bond and formation of new bonds.Hence new substance with completely different properties is formed. These changes occur only in a chemical reaction .
In physical processes no new substance is formed (no bonding).So,no change in properties of a substance . ]
This process (capability of bonding to surfaces with the application of light pressure) results in chemical reaction.
This type of substances are called Pressure-sensitive Adhesives.(PSA)
Given the chemical formula, KNO3, what is the percent nitrogen in the compound?
A) 13.86%
B) 14.01%
C) 38.36%
D) 47.48%
please help
Answer:
The answer to your question is letter A
Explanation:
Process
1.- Calculate the molar mass of KNO₃
KNO₃ molecular mass = 39.1 + 14.01 + (3 x 16)
= 39.1 + 14.01 + 48
= 101.11 g
2.- Use a rule of three to find the percent of nitrogen
101.11 g of KNO₃ --------------- 100%
14.01 g of N --------------- x
x = (14.01 x 100) / 101.11
x = 13.86%
If an equal quantity of heat is transferred to 10.0 g samples of liquid water (C = 4.184 J/g°C), concrete (C = 0.88 J/g°C), asphalt (C = 0.920 J/g°C), glass (C = 0.84 J/g°C), and iron (C = 0.448 J/g°C), rank the final temperatures of the samples from least to greatest.
Answer:
The ranking is given as; Water > Asphalt > Concrete > glass > Iron
Explanation:
The trick in solving this question is to assume a constant heat value; in this case i'll be choosing 100 J. Use this value to solve for the temperature difference. from that we can be able to rank the samples in order of their temperatures.
The formular to be used here is the;
H = MCΔT
Where;
H = Heat
M = Mass
C = Heat Capacity
ΔT = Temperature difference
ΔT = H/MC
In water;
ΔT = 100 / (10 * 4.184) = 2.39K
In Concrete;
ΔT = 100 / (10 * 0.88) = 11.36K
In asphalt;
ΔT = 100 / (10 * 0.920) = 10.87K
In glass;
ΔT = 100 / (10 * 0.84) = 11.9K
In iron;
ΔT = 100 / (10 * 0.448) = 22.3K
The samples with least temperature difference would have final temperatures and vice versa.
Our ranking is the given as; Water > Asphalt > Concrete > glass > Iron
The ranking from the least final temperature to the greatest is liquid water, asphalt, concrete, glass, iron.
The question involves understanding the concept of specific heat capacity in relation to the final temperature of different materials after the same quantity of heat is transferred. The specific heat capacity (C) is a property that defines how much heat energy is required to raise the temperature of a unit mass of a substance by one degree Celsius. The materials listed are liquid water, concrete, asphalt, glass, and iron, with specific heat capacities of 4.184 J/g°C, 0.88 J/g°C, 0.920 J/g°C, 0.84 J/g°C, and 0.448 J/g°C, respectively.
Given the relationship that the amount of heat (Q) added or removed is directly proportional to the mass (m), specific heat capacity (C), and change in temperature (ΔT), we have Q = mCΔT. With an equal amount of heat transferred and the same mass for each sample, substances with a higher specific heat capacity will experience a smaller change in temperature. Thus, to rank the final temperatures from least to greatest after the equal heat transfer, we should look at the specific heat capacities in reverse order, as a lower specific heat capacity means more temperature change for the same amount of heat.
Iron (C = 0.448 J/g°C), Glass (C = 0.84 J/g°C), Concrete (C = 0.88 J/g°C), Asphalt (C = 0.920 J/g°C), Liquid Water (C = 4.184 J/g°C)
Therefore, the final temperatures of the samples, from least to greatest, will be as follows: iron will have the highest final temperature, followed by glass, concrete, asphalt, and liquid water will have the lowest final temperature.
Chromium may help lower the risk of __________ by increasing the effectiveness of _____.
Answer:
type 2 diabetes
insulin
Explanation:
type 2 diabetes is a chronic condition that affects the way the body processes blood sugar. A patient with type 2 diabetes in the body either doesn't produce enough insulin, or it resists insulin.
As Chromium levels can be below normal in people with type 2 diabetes. Research studies shows that taking drugs that contains chromium such as chromium picolinate can help increase the effectiveness of insulin levels and help insulin work in people with type 2 diabetes.
Apply the Law of Conservation of Mass to the following problem: During a combustion reaction, 12.2 grams of methane reacts with 14 g of oxygen. The reaction produces carbon dioxide and water. If 20 grams of water are produced, how many grams of carbon dioxide are produced?
Answer:
5.8 g of carbon dioxide are produced
Explanation:
The Law of Conservation of Mass states that the mass of the reactants must equal the mass of the products in all chemical reactions.
This is the chemical reaction (combustion)
CH₄ + 2O₂ → CO₂ + 2H₂O
12.2 g 14 g x 20g
Mass in reactants = 12.2 g + 14 g = 26.2 g
Mass in products = x + 20 g
26.2 g = x + 20g
26.2 g - 20g = x
5.8 g = x
Why did J.J. Thomson reason that electrons must be a part of the atoms of all element
Answer:
Same particles (electrons) were emitted even after changing the cathode material.
Explanation:
In his famous experiment, Thompson tested the properties of atomic particles. He used a cathode ray tube to apply voltage on the cathode. This generated beam of electrons, also called cathode rays. He bombarded the rays on phosphorus on the other end of the tube, to observe the pathway it took.
When he noticed the deflection of cathode rays when it passes through the electric and magnetic field, he repeated the experiment by changing the cathode material. To his surprise, rays emitted from all the materials exhibited the same behavior.
He concluded that these rays comprising of electrons, are a fundamental part of atoms of every element.
Draw the product of the following reaction between a ketone and an alcohol.
Answer:
The product of the reaction between a ketone and an alcohol is initially a hemiketal which yields a ketal on further reaction with another alcohol molecule.
The structure is found in the attachment.
Explanation:
This reaction is a nucleophilic addition to the carbonyl group. In organic chemistry, a nucleophilic addition reaction is an addition reaction where a chemical compound with an electron-deficient or electrophilic double or triple bond, a pi (π) bond, reacts with electron-rich reactant, termed a nucleophile, with the elimination of the double bond and creation of two new single, or sigma (σ), bonds.
In the reaction between a ketone and an alcohol, the carbonyl group of the ketone serves as the electrophile while the hydroxyl group of the alcohol is the nucleophile. The first product is known as a hemiketal because a single alcohol group has been aded to the carbonyl group of the ketone. Further nucleophilic additon of an alcohol group initiated by the presence of an acid e.g hydrochloric acid, results in the formation of a ketal which has two alcohol group added to the original ketone.
Final answer:
The reaction between a ketone and an alcohol can produce a hemiketal or ketal, depending on the reaction conditions and the excess of alcohol. A hemiketal is formed when the alcohol reacts with the ketone to form a new carbon-oxygen bond, while a ketal is formed when a second molecule of alcohol reacts to convert the hemiketal into a stable compound.
Explanation:
In the reaction between a ketone and an alcohol, the product formed is called a hemiketal or ketal, depending on the reaction conditions and the presence of excess alcohol. A hemiketal is formed when the alcohol reacts with the ketone to form a new carbon-oxygen bond, while a ketal is formed when a second molecule of alcohol reacts to convert the hemiketal into a stable compound.
For example, if we take the ketone acetone (CH3C=O) and react it with ethanol (CH3CH2OH), we can form a hemiketal:
CH3C(OC2H5)(OH)
If we add excess ethanol, the hemiketal can react with a second molecule of ethanol to form a ketal:
CH3C(OC2H5)2
The reaction can also occur between other ketones and alcohols, resulting in the formation of different hemiketals or ketals.
An element is in Group 15. The last electron added to an atom of this element will be in a(n) __ sublevel
a. p
b. d
c. f
d. s
Answer:
a
Explanation:
Group 15 form trihydrides with the non metal atoms like phosphine, ammonia
According to the VSEPR model, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the:_________
Answer:
Presence of lone pairs of electrons
Explanation:
According to VSEPR theory, the presence of lone pairs caused increased repulsion of electron pairs on the valence shell of the centeral atom of the molecule. This decreases or distorts the bond angle. The decrease in bond ange depends on the number of lone pairs present on the valence shell of the central atom of the molecule. Ammonia has only one lone pair hence the bond angle is 107°, water has two lone pairs and the bond angle is 104°. Compare this this with the bond angle of 109° in methane which has only bond pairs and no lone pairs.
The decrease in bond angles from CH4 to NH3 to H2O is due to increasing number of lone pairs on the central atom which cause greater repulsion and smaller bond angles, as per the VSEPR theory.
Explanation:According to the Valence shell electron-pair repulsion (VSEPR) theory, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the presence and arrangement of lone electron pairs on the central atom. CH4 has no lone pairs on the central carbon atom and has a tetrahedral shape with bond angles of 109.5°. In NH3, the nitrogen atom has one lone pair, which decreases the bond angle to less than 109.5°. In H2O, the oxygen atom has two lone pairs, leading to an even smaller bond angle of 104.5°. The VSEPR theory predicts that the electron pairs will arrange themselves to minimize repulsion, and the lone pair-lone pair repulsion is greatest, followed by lone pair-bonding pair, and finally, bonding pair-bonding pair repulsion is the least.
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In order to get lots of helium into tanks to fill kiddy balloons, they put force or pressure onto it. If i have 595 liters of helium at 1.00 atmosphere of pressure (that’s normal air pressure, or the pressure of the air), then what volume would it have if i applied 55.0 atmospheres of force or pressure to it?
Answer:
1.90 L
Explanation:
Using Boyle's law
[tex]{P_1}\times {V_1}={P_2}\times {V_2}[/tex]
Given ,
V₁ = 595 L
V₂ = ?
P₁ = 1.00 atm
P₂ = 55.0 atm
Using above equation as:
[tex]{P_1}\times {V_1}={P_2}\times {V_2}[/tex]
[tex]{1.00}\times {595}={55.0}\times {V_2}[/tex]
[tex]{V_2}=\frac{{1.00}\times {595}}{55.0}\ L[/tex]
[tex]{V_2}=1.90\ L[/tex]
The volume would be 1.90 L.
Problem 2: 1. Represent a molecule of 1-butene [1] 2. 1-Butene reacts with a molecule of bromine,Br2. (reaction 1) a. Is bromine polar or apolar? Explain [1] b. Write the equation for the reaction. Identify nucleophile and electrophile in the reaction. Show the mechanism of the reaction stepwise using curved arrows. Specify the type of reaction. [4] c. Why does the reaction take place with bromine? [2] d. What is the name of the main product? [1]
Answer:
See explanation below
Explanation:
The drawing of the molecule and mechanism, you can see it in the attached pictures.
Now, answering the theorical questions:
The 1-butene is like this:
CH2 = CH - CH2 - CH3
If this molecule reacts with bromine (Br2) the reaction and product formed is:
CH2 = CH - CH2 - CH3 + Br2 -----------> Br-CH2 - CH(Br) - CH2 - CH3
The product formed is called 1,2 - dibromo - butane, and the reaction with halides like bromine is called halogenation. In this case, alkenes halogenation, so, we become a alkene like the 1-butene with a halide like bromine to form an alkane with halides. This reaction is taking place in conditions of Sn1, although this is an addition (Two steps, see picture below for mechanism).
The bromine, has a high electronegativity (2.9) this is even bigger than the iodine (2.7), so, when the bromine acts as a nucleophile in a SN2 or SN1 reaction (like this one), bromine atom becomes slightly more negative, and iodine atom becomes slightly more positive, so strictly speaking, the molecule is slightly polar. When the difference of the electronegativities is below of 0.4, we can say that the molecule is non-polar.
Because of the explanation above, the reaction is taking place with bromine, because it has a higher electronegativity, even more than the chlorine, so the molecule is more polar and can have a better reaction with the 1-butene than the chlorine. Has a better nucleophyle attack and also, is a great leaving group.
The picture below will show the mechanism:
Cindy predicts that plastic foam insulates cold drinks better than metal or ceramic materials do. To test the hypothesis, she fills cups made from these materials with equal amounts of cold water. She records the temperature of the water in each cup, using scientific thermometers, every 10 minutes until the water reaches room temperature. Which of these conditions must be the same for this experiment to be valid?
A. the thermometer that is in each cup
B. the starting temperature of the water in each cup
C. the ending temperature of the water in each cup
D. the material that makes up each cup
Answer:
B. The starting temperature of the water in each cup
Explanation:
Cindy is trying to see if foam or ceramic is a better insulator. Those are her independent variables.
The other variables , like the starting temperature of the water in each cup, must be controlled variables. If she uses different starting temperatures in each cup, she won't know if it was the temperature or the materials that caused her results.
A. is wrong. The thermometers should be identical but, if they aren't, it will make little difference in the results.
C. is wrong. The ending temperature is room temperature, so it is automatically the same for each cup.
D. is wrong. She is trying to measure the effect of different materials.
Answer:the answer is B(the starting temperature of the water in each cup)
Explanation:
. If 84 grams of sodium chloride reacts with an excess amount of magnesium oxide, how many grams of sodium oxide will be produced? Question 2 options: 23.2 g Na20 45g MgCl2 107g MgO 44.5g Na20
Answer:
44.5 g of Na₂O
Explanation:
The reaction is this one:
2NaCl + MgO → Na₂O + MgCl₂
Moles of NaCl = Mass / Molar mass
84 g / 58.45 g/m = 1.43 moles
Ratio is 2:1, so if we produce 1 mol of Na₂O, from 2 moles of NaCl; If we have 1.43 moles, we 'll produce the half of moles
1.43 / 2 = 0.72 moles
Molar mass Na₂O = 62 g/m
Mol . molar mass = 0.72 m . 62 g/m = 44.5 g
Answer:
There will be 44.5 grams of sodium oxide (Na2O) produced
Explanation:
Step 1: Data given
Mass of Sodium chloride (NaCl) = 84.00 grams
Magnesium oxide = in excess
Molar mass of NaCl = 58.44 g/mol
Molar mass of sod)ium oxide (Na2O = 61.98 g/mol
Step 2: The balanced equation
2NaCl + MgO → Na2O + MgCl2
Step 3: Calculate moles of NaCl
Moles NaCl = Mass / Molar mass
Moles NaCl = 84.00 grams / 58.44 g/mol
Moles NaCl = 1.437 moles
Step 4: Calculate moles of Na2O
The limiting reactant is NaCl.
For 2 moles NaCl consumed, we need 1 mol MgO to produce 1 mol Na2O and 1 mol of MgCl2
For 1.437 moles of NaCl we'll have 1.437/2 = 0.7185 moles of Na2O
Step 5: Calculate mass of Na2O
Mass Na2O = Moles Na2O * Molar mass Na2O
Mass Na2O = 0.7185 moles * 61.98 g/mol
Mass Na2O = 44.53 grams of Na2O
There will be 44.5 grams of sodium oxide (Na2O) produced
What mass of gold is produced when 17.6^A of current are passed through a gold solution for 37.0 min ?
Answer:
There is 26.58 grams of gold formed
Explanation:
Step 1: Data given
17.6 A of current are passed through a gold solution for 37.0 min
Molar mass of Au = 196.967 g/mol
Step 2: The equation
Au^3+ + 3e- → Au
Step 3: Calculate coulombs
17.6 Coulomb/s * 37.0 min * 60 sec/min = 39072 Coulombs
1 Faraday = 96500 Coulombs
Step 4: Calculate faraday
39072 Coulombs / 96500 Coulombs / Faraday = 0.40489 Faraday
Step 5: Calculate mass of gold formed
For every 3 Faraday of electricity used up , 1 mole Au is formed
0.40489 Faraday * 1 mole Au/ 3 Faraday = 0.13496 mole Au
196.967 g/mol * 0.13496 mol = 26.58 g Au
There is 26.58 grams of gold formed
The mass of gold that is produced is 26.59 g
Using the formula
[tex]m = \frac{Atomic\ mass}{nF}\times It[/tex]
Where m is the mass
n is the number of equivalents
F is the Faraday constant ( F = 96485 C)
I is the current
and t is the time
From the given information
I = 17.6 A
t = 37.0 min = 37.0 × 60
t = 2220 secs
For gold
Atomic mass = 196.97 g/mol
and n = 3
Putting these parameters into the formula, we get
[tex]m = \frac{196.97}{3 \times 96485} \times 17.6 \times 2220[/tex]
[tex]m = \frac{7696011.84}{289455}[/tex]
m = 26.59 g
Hence, the mass of gold that is produced is 26.59 g
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Some insects can glide across the surface of water due to water's: hydrogen bonds. viscosity. capillarity. polarity. surface tension
Answer: surface tension
Explanation: the tiny weight of insect is not strong enough to break the surface tension of water. So when insects stands or move on water, their feets creates something like dimples on the surface of water which then spring back to propel the insect forward thereby preventing them from sinking.
Consider atoms of the following elements. Assume that the atoms are in the ground state.
(A) S(B) Ca(C) Ga(D) Sb(E) Br2. The atom that contains only one electron in the highest occupied energy sublevel
Answer:
C
Explanation:
Gallium is in group thirteen with outermost electron configuration ns2 np1. The highest occupied sub-level is np1 having only one electron which is the situation required in the question.
Answer:
C. Ga
Explanation:
According to the equation above, how many moles of potassium chlorate, KClO3, must be decomposed to generate 1.0 L of O2 gas at standard temperature and pressure?
Answer:
Moles of potassium chlorate = 0.02976 moles
Explanation:
At standard pressure and temperature,
22.4 L of a gas consists of 1 mole
Thus, given, volume of [tex]O_2[/tex] = 1.0 L
So,
1 L of a gas consists of [tex]\frac{1}{22.4}[/tex] mole
Moles of oxygen gas = 0.04464 moles
The reaction is shown below as:-
[tex]2KClO_3\rightarrow 2KCl+3O_2[/tex]
3 moles of oxygen gas are produced when 2 moles of potassium chlorate undergoes reaction.
So,
1 mole of oxygen gas are produced when [tex]\frac{2}{3}[/tex] moles of potassium chlorate undergoes reaction.
Thus,
0.04464 mole of oxygen gas are produced when [tex]\frac{2}{3}\times 0.04464[/tex] moles of potassium chlorate undergoes reaction.
Moles of potassium chlorate = 0.02976 moles
From the decomposition reaction 2KClO₃(s) → 2KCl(s) + 3O₂(g), the number of moles of KClO₃ to be decomposed to generate 1.0 L of O₂ gas at standard temperature and pressure (STP) is 0.030.
The balanced chemical reaction for the decomposition of potassium chlorate (KClO₃) is the following:
2KClO₃(s) → 2KCl(s) + 3O₂(g) (1)
We can find the number of moles of O₂ gas with the Ideal gas equation:
[tex] PV = nRT [/tex]
Where:
P: is the pressure = 1.0 atm (at STP conditions)
V: is the volume = 1.0 L
R: is the gas constant = 0.082 L*atm/(K*mol)
T: is the temperature = 273 K (at STP conditions)
n: is the number of moles =?
The number of moles of O₂ gas is:
[tex] n_{O_{2}} = \frac{PV}{RT} = \frac{1.0 atm*1.0 L}{0.082 L*atm/(K*mol)*273 K} = 0.045 \:moles [/tex]
From reaction (1), we have that 2 moles of KClO₃ produce 3 moles of O₂, so the number of moles of KClO₃ resulting from the decomposition is:
[tex] n_{KClO_{3}} = \frac{2\:moles\:KClO_{3}}{3\:moles\:O_{2}}*0.045\:moles\:O_{2} = 0.030 \:moles [/tex]
Therefore, the number of KClO₃ moles to be decomposed is 0.030.
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When scientists use one of their five senses to gather information, they are A. making an observation. B. making an inference. C. predicting a relationship D. drawing a conclusion.
The scientists use one of their five senses to gather information, they are making an observation.
What is an observation ?The active gathering of data from a primary source is observation. Observation of living things makes use of the senses. Using scientific tools to perceive and record data is another way that observation may be used in science.
A technique for gathering information through observation of individuals, situations, or physical qualities as they are occurring naturally.
Using one or more senses, our observational abilities provide us with knowledge about things, occasions, attitudes, and occurrences. Being able to see and learn about the outside world is crucial because it forms the basis of effective communication.
Thus, option A is correct.
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In scientific endeavors, when one of the five senses is used to gather information, it constitutes making an observation. Observations can involve both qualitative and quantitative data, and they provide evidence that scientists use to form conclusions.
Explanation:When scientists use one of their five senses to gather information, they are A. making an observation. Scientists usually perform observations by using one or more of their five senses to gain an understanding of the properties or behaviors of a substance or a system. These data can be qualitative (descriptive) or quantitative (consisting of numbers). For instance, seeing a plant growing (observation) and measuring its growth over weeks (data collection). From these observations, the scientist can infer conclusions based on the evidence collected. In brain studies, the activity in the brain during specific tasks is observed, which could be the basis for conclusions about brain functionality.
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Calculate the standard entropy of vaporization of ethanol at its boiling point
The question is incomplete, here is a complete question.
Calculate the standard entropy of vaporization of ethanol at its boiling point 352 K. The standard molar enthalpy of vaporization of ethanol at its boiling point is 40.5 kJ/mol.
Answer : The standard entropy of vaporization of ethanol is, 115 J/mol.K
Explanation :
Formula used :
[tex]\Delta S=\frac{\Delta H_{vap}}{T_b}[/tex]
where,
[tex]\Delta S[/tex] = change in entropy
[tex]\Delta H_{vap}[/tex] = change in enthalpy of vaporization = 40.5 kJ/mol
[tex]T_b[/tex] = boiling point temperature = 352 K
Now put all the given values in the above formula, we get:
[tex]\Delta S=\frac{\Delta H_{vap}}{T_b}[/tex]
[tex]\Delta S=\frac{40.5kJ/mol}{352K}[/tex]
[tex]\Delta S=\frac{40.5\times 10^3J/mol}{352K}[/tex]
[tex]\Delta S=115J/mol.K[/tex]
Therefore, the standard entropy of vaporization of ethanol is, 115 J/mol.K
Calcium has a cubic closest packed structure as a solid. Assuming that calcium has an atomic radius of 197 pm, calculate the density of solid calcium.
Answer:
[tex]\rho=1.54\ g/cm^3[/tex]
Explanation:
The expression for density is:
[tex]\rho=\frac {Z\times M}{N_a\times {{(Edge\ length)}^3}}[/tex]
[tex]N_a=6.023\times 10^{23}\ {mol}^{-1}[/tex]
M is molar mass of Calcium = 40.078 g/mol
For cubic closest packed structure , Z= 4
[tex]\rho[/tex] is the density
Radius = 197 pm = [tex]1.97\times 10^{-8}\ cm[/tex]
Also, for fcc, [tex]Edge\ length=2\sqrt{2}\times radius=2\sqrt{2}\times 1.97\times 10^{-8}\ cm=5.572\times 10^{-8}\ cm[/tex]
Thus,
[tex]\rho=\frac{4\times \:40.078}{6.023\times \:10^{23}\times \left(5.572\times 10^{-8}\right)^3}\ g/cm^3[/tex]
[tex]\rho=\frac{160.312}{10^{23}\times \:6.023\left(10^{-8}\times \:5.572\right)^3}\ g/cm^3[/tex]
[tex]\rho=\frac{160.312}{10^{23}\times \:1.04195E-21}\ g/cm^3[/tex]
[tex]\rho=\frac{160.312}{104.19483}\ g/cm^3[/tex]
[tex]\rho=1.54\ g/cm^3[/tex]
The density of solid calcium can be calculated by determining the density of its unit cell using the face-centered cubic (FCC) structure. The mass and volume of the unit cell can be calculated using the atomic radius and atomic mass of calcium. Dividing the mass by the volume gives the density of solid calcium.
Explanation:The density of solid calcium can be calculated by determining the density of its unit cell, which is a face-centered cubic (FCC) structure. In an FCC structure, each unit cell contains 4 atoms. The mass of 4 calcium atoms can be calculated using the atomic mass of calcium, and the volume of the unit cell can be calculated using the atomic radius of calcium. Dividing the mass by the volume gives the density of solid calcium.
The atomic radius of calcium is given as 197 pm, which can be converted to cm by multiplying by 10^-10. The volume of the unit cell can be calculated using the formula V = (edge length)^3. The edge length can be calculated using the diagonal of the face, which is 4 times the atomic radius. The mass of 4 calcium atoms can be calculated using the atomic mass of calcium, which is 40.08 g/mol. Dividing the mass by the volume gives the density of solid calcium.
Density of solid calcium = mass of 4 Ca atoms / volume of unit cell
Keywords: density, solid calcium, unit cell, face-centered cubic (FCC) structure, atomic radius, atomic mass
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Why can the positive ions be considered to be fixed during the electrons’ oscillations?
Final answer:
Positive ions, which form the nucleus, are considered fixed during the electrons’ oscillations due to their significantly larger mass, which makes them relatively stationary compared to the lightweight and mobile electrons. In atomic models, this assumption simplifies the study of electronic behavior.
Explanation:
Positive ions can be considered to be fixed during the electrons’ oscillations because of their relatively large mass compared to electrons. In the context of atomic physics and the Bohr model, positive ions are essentially the nucleus of an atom, which is comprised of protons and neutrons. These particles are much heavier than the electrons and thus remain relatively stationary when the electrons oscillate or move in their orbits.
Within the atom, cations, which are positive ions, are created when elements lose one or more electrons. For example, group 1 elements in the periodic table lose one electron easily due to their electronic configuration, leading to a positive charge. The difference in mass means that while the electrons, which are lightweight and mobile, can oscillate or change their energy states quickly, the heavier protons in the nucleus (the cations) do not move significantly during these processes. Consequently, in many atomic models and explanations of electronic behavior, the positive ions are often treated as if they are fixed in place.
A 360mg sample of aspirin, C9H8O4, (molar mass 180g), is dissolved in enough water to produce 200mL of solution. What is the molarity of aspirin in a 50mL sample of this solution?
The molarity of the 360mg aspirin sample dissolved in 200mL solution is found to be 0.01 M. As molarity is a measure of concentration, it remains the same in a 50mL sample of the solution. Therefore, the molarity of the aspirin in the 50mL solution is also 0.01 M.
Explanation:To calculate the molarity of the aspirin in a 50mL sample, first the molarity of the original 200mL solution is calculated. The molarity (M) is defined as moles of solute (in this case aspirin) per liters of solution. The moles of aspirin in the 360mg sample can be calculated by dividing by the molar mass of aspirin, which is 180g/mol. Thus, there are 0.002 mol (360mg * 1g/1000mg * 1 mol/180g) of aspirin in the 200mL solution. Converting mL to L (200mL * 1L/1000mL), the molarity of the 200mL solution is 0.002 mol / 0.2 L = 0.01 M.
Since molarity is a concentration, it remains the same regardless of the volume of the solution: thus, the molarity of the 50mL sample of the solution is also 0.01 M. So, the molarity of aspirin in a 50mL sample of the solution is 0.01 M.
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Describe light with respect to its speed and its dual nature as both a wave and a particle.
Answer:
Scientists have been debating over light being a wave or particle since its recognition.
Sir Issac Newton discovered that light had frequency and other properties. Newton described light to be a particle because it created shadows which were sharp and very clear.
Francesco Maria Grimaldi, claimed that light was a wave. This was because this scientist observed the diffraction of light and hence, claimed light to be a type of wave.
The speed of light is 299 792 458 m / s. Nothing can travel faster than light.
Element Z has 2 natural isotopes. One isotope has a mass of 15.0amu and has a relative abundance of 30%. The other isotope has a mass of 16.0amu and has a relative abundance of 70%. Estimate the average atomic mass for this element to one decimal place.
Answer:
The answer to your question is 15.7 amu
Explanation:
Abundance Mass
Isotope 1 30% 15
Isotope 2 70% 16
Average atomic mass = (Abundance isotope 1 x abundance) +
(Abundance isotope 2 x abundance)
Substitution
Average atomic mass = (0.30 x 15) + (0.70 x 16)
Simplify
Average atomic mass = 4.5 + 11.2
Result
Average atomic mass = 15.7 amu
A 4.00 g sample of a metal (specific heat = 0.600 J g-1°C-1 is heated to 75 degrees Celcius and then dropped into 165 g of water in a calorimeter. What is the final temperature of the water if the initial temperature is 28 degrees Celcius? The specific heat capacity of water is 4.184 J/g.°C.
Answer:
28.16 °C
Explanation:
Considering that:-
Heat gain by water = Heat lost by metal
Thus,
[tex]m_{water}\times C_{water}\times (T_f-T_i)=-m_{metal}\times C_{metal}\times (T_f-T_i)[/tex]
Where, negative sign signifies heat loss
Or,
[tex]m_{water}\times C_{water}\times (T_f-T_i)=m_{metal}\times C_{metal}\times (T_i-T_f)[/tex]
For water:
Mass = 165 g
Initial temperature = 28 °C
Specific heat of water = 4.184 J/g°C
For metal:
Mass = 4.00 g
Initial temperature = 75 °C
Specific heat of water = 0.600 J/g°C
So,
[tex]165\times 4.184\times (T_f-28)=4.00\times 0.600\times (75-T_f)[/tex]
[tex]690360\left(T_f-28\right)=2400\left(75-T_f\right)[/tex]
[tex]692760T_f=19510080[/tex]
[tex]T_f = 28.16\ ^0C[/tex]
Hence, the final temperature is 28.16 °C