How much of a 100.0 g sample of 198au is left after 8.10 days ifi its half life is 2.70 days?

Answer;

-Research and development

Scientists in research and development discover new products and processes and improve current technology.

Explanation;

Research scientists are responsible for designing, undertaking and analyzing information from controlled laboratory-based investigations, experiments and trials.

Additionally, research and development is an important means for achieving future growth and maintaining a relevant product in the market. Research may be basic research and applied research applied.  Development is when findings of a research are utilized for the production of specific products including materials, systems and methods.

Final answer:

The error in the electron configuration 1s2 2s2 2p6 3s2 3p5 4s2 is that it places electrons in the 4s sublevel before filling the 3d sublevel. The correct order should fill the 3d sublevel before the 4s according to the Aufbau principle.

Explanation:

The student's question is about identifying the error in the given electron configuration, which is 1s2 2s2 2p6 3s2 3p5 4s2. The error in this configuration is the arrangement of electrons in the 4s sublevel before the 3d sublevel is filled. According to the Aufbau principle, which dictates the order in which sublevels are filled based on increasing energy, after the 3p sublevel is filled, electrons should start filling the 3d sublevel before the 4s. However, in the given configuration, it incorrectly shows two electrons in the 4s sublevel before the 3d sublevel has any electrons. The correct electron configuration after 3p6 should be 3d1 before moving to 4s1 or 4s2 depending on the element in question. For example, the correct configuration for potassium (Z=19) is 1s²2s²2p63s²3p64s¹, and for calcium (Z=20), it is 1s²2s²2p63s²3p64s².

The oxygen element has an electronic configuration that ends with 2s²2p⁴.

The electron configuration can describe how electrons are arranged in different energy levels of an atom of an element. In the electron configuration of an atom, the number of electrons in a particular atomic orbital is written as a superscript. For example, the electron configuration of Helium (He) is written as 1s²2s².

The principal quantum number (n) will decide the maximum number of electrons that can be filled in a shell and is determined from the term 2n², where ‘n’ is the principal quantum number.

The atomic orbitals of an atom of a lower energy level should be completely filled before filling an atomic orbital with a higher energy level.

The atomic number of the oxygen atom is 8 and the electronic configuration is 1s²2s²2p⁴. It has six electrons in its valence shell and an electronic configuration ends with 2s²2p⁴.

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Answer: Option (d) is the correct answer.

Explanation:

Noble gases are the gases of group 18 which are helium, neon, argon, krypton, xenon and radon.

For example, electronic configuration of neon is [tex]1s^{2}2s^{2}2p^{6}[/tex]

These elements have completely filled shells so, they do not need to gain or lose an electron as they are stabilized.

As a result, noble gases become unreactive in nature.

Thus. we can conclude that noble gases is the name of the group of elements that are unreactive gases.

A + B → AB:  ✔ synthesis

AB → A + B: ✔ decomposition

Hydrocarbon + O2 → CO2 + H2O:  ✔ combustion

AB + CD → AD + CB:  ✔ replacement

Generic chemical equation for combination, decomposition, displacement and double displacement reactions are given as A+B=AB, AB=A+B,AB+C=AC+B and AB+CD=AC+BD  respectively.

Chemical equation is a symbolic representation of a chemical reaction which is written in the form of symbols and chemical formulas.The reactants are present on the left hand side while the products are present on the right hand side.

A plus sign is present between reactants and products if they are more than one in any case and an arrow is present pointing towards the product side which indicates the direction of the reaction .There are coefficients present next to the chemical symbols and formulas .

The first chemical equation was put forth by Jean Beguin in 1615.By making use of chemical equations the direction of reaction ,state of reactants and products can be stated. In the chemical equations even the temperature to be maintained and catalyst can be mentioned.

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 The   mass  of each  elements   in  chromite is as below

Fe  =24.9 %

Cr  =46.5%

O = 28.6%

calculation

percent  mass  =  atomic mass  of  element / atomic mass of FeCr2O4 x 100

from  periodic table  the atomic mass  for  Fe  = 55.85 g/mol,

Cr =52 g/mol  since  they  are two  atoms  in FeCr2O4 =  2 x 52 = 104 g/mol

for  O  = 16   since  they are two  atoms in FeCr2O4 =  16  x4  =  64  g/mol

Atomic mass for  FeCr2O4  is  = 55.85 +104+  64  = 223.85  g/mol

Percent  mass  for Fe  =55.85 /223.85  x100  = 24.9 %

                          for  Cr =  104 / 223.85  x 100  = 46.5%

                           For 0  =  64/223.85  x 100  =  28.6%

The vapour pressure of a substance actually differs relative to the temperature. So to know which compound has the vapour pressure of 58 kilopascals at 65 degrees Celsius, we refer to standard tables of temperature vs Vapour pressure.

From the tables or graph, the answer here is:

2. ethanol

Answer: 2. Ethanol

Explanation:

Answer:

The correct option is C

Explanation:

For a reaction to occur, there is a minimum amount of energy that must be "met". This minimum amount of energy is called activation energy. Activation energy is the minimum amount of energy required for a reaction to occur. When this activation energy is high, it takes a longer time for the reaction to occur, hence it slows down the rate of a chemical reaction but when the activation energy is low, the rate of a chemical reaction is increased.

A catalyst is known to increase the rate of a chemical reaction - it does this by reducing the activation energy of the reaction, providing an alternative reaction pathway for the reaction.

The molarity of CO2 in a water solution with a mole fraction of 0.25, assuming the density of the solution is 1.0 g/mL, is calculated to be 0.04401 M.

To determine the molarity of carbon dioxide (CO2) in a solution with a mole fraction (xCO2) of 0.25, and a density of 1.0 g/mL, we need to use the definition of mole fraction alongside the known density of the solution. The mole fraction is the ratio of the moles of solute to the total moles in the solution. Assuming we have one liter of solution and know that the density is 1.0 g/mL, the total mass of the solution is 1000 g.

First, we calculate the total moles of the solution. Since the mole fraction of CO2 is 0.25, this means that 25% of the moles are CO2. To find the molarity of CO2, we need to find the mass of CO2 based on its mole fraction and then convert this to moles.

Since we are given the mole fraction and we know the density of the solution, we can calculate the mass of CO2 in one liter of solution. Let's assume a total of 4 moles of substance are present (as 0.25 is one-fourth). Hence, one mole of CO2 is present because the mole fraction of CO2 is 0.25. Knowing that the molar mass of CO2 is 44.01 g/mol, we find that the mass of 1 mole of CO2 is 44.01 grams. The molarity is found by dividing the moles of CO2 by the volume of the solution in liters, which gives a molarity of 0.04401 M.

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Answer is: cooling.

Cooling is change from liquids to solids.

Another example is crystalisation, many elements and compounds form crystals.

A physical change occurs when a substance changes phase.

Physical property can be observed and measured without any changes in molecular composition. The same substance is present before and after the change.

The potential energy of a gas decreases during a phase change, such as cooling and condensing to a liquid.

The potential energy of a gas decreases during a phase change when a large amount of energy is extracted from the system and causes a decrease in the gas's volume, pressure, or both. For example, when a gas is cooled and condenses to a liquid, its potential energy decreases. This is illustrated by a graph of pressure vs. temperature, where the pressure of a gas continually decreases as it is cooled at a constant volume.

Final answer:

To find the heat produced by the combustion of 2 mol of methane gas, you use the standard enthalpies of formation. The calculated heat produced is -1630.6 kJ.

Explanation:

The question involves using the concept of enthalpy change (ΔH), specifically standard enthalpies of formation (ΔH°f), to calculate the heat produced during the combustion of methane gas (CH4).

Step-by-Step Calculation:

First, write down the balanced chemical equation for the combustion of methane:

CH4(g) + 2O2(g) → CO2(g) + 2H2O(№)

Next, apply Hess's Law using the provided ΔH°f values:

CH4(g): -74.9 kJ/mol

CO2(g): -393.5 kJ/mol

H2O(№): -285.8 kJ/mol

Calculate the total enthalpy change (ΔH) for the reaction:

ΔH = [1 mol(ΔH°f CO2) + 2 mol(ΔH°f H2O)] - [2 mol(ΔH°f CH4)]

ΔH = [1 mol(-393.5 kJ/mol) + 2 mol(-285.8 kJ/mol)] - [2 mol(-74.9 kJ/mol)]

ΔH = (-393.5 kJ - 2×285.8 kJ) - (-2×74.9 kJ)

ΔH = (-393.5 - 571.6 + 149.8) kJ

ΔH = -815.3 kJ

This is the enthalpy change for the combustion of 1 mol of methane. Since we are burning 2 mol of methane, multiply by 2:

Total ΔH = 2 × -815.3 kJ

Total ΔH = -1630.6 kJ

Therefore, the heat produced by burning 2 mol of methane gas is -1630.6 kJ.

B. iron, copper, ruthenium

Answer: The correct answer is Option D.

Explanation:

Elements which belong to same group show similar chemical properties because they have same number of valence electrons.

From the given options:

Option A: Cobalt belongs to Group 9, Iron belongs to Group 8 and Nickel belongs to Group 10. Hence, they will not show similar chemical properties.

Option B: Iron belongs to Group 8, Copper belongs to Group 11 and Ruthenium belongs to Group 8. Hence, they will not show similar chemical properties.

Option C: Ruthenium belongs to Group 8, Iridium belongs to Group 9 and Palladium belongs to Group 10. Hence, they will not show similar chemical properties.

Option D: Gold, Silver and Copper belongs to the same group which is Group 11. Hence, they all will show similar chemical properties.

Thus, the correct answer is Option D.

Final answer:

The Oklahoma City bombing on April 19, 1995, utilized a truck bomb made from ammonium nitrate fertilizer mixed with fuel oil. The terrorists hoped to incite a revolution against government control. The attack killed 168 people, injured over 600, and resulted in widespread destruction.

Explanation:

The type of bomb used in the Oklahoma City bombing of April 19, 1995, was a truck bomb. Timothy McVeigh and Terry Nichols constructed the explosive using agricultural grade ammonium nitrate fertilizer mixed with fuel oil, packing the mixture into a rented Ryder truck. This deadly attack led to the loss of 168 lives, including nineteen children, and left over 600 individuals injured. The bombing severely damaged the Alfred P. Murrah Federal Building, along with more than three hundred nearby buildings. The motivations of McVeigh were associated with a desire to start a revolution against government authority, partly in retaliation for the Waco siege that occurred exactly two years prior.

The aftermath of the bombing united Americans across the country, bringing forth an outpouring of generosity and support for the victims and their families. President Bill Clinton's speech helped galvanize the nation towards unity and reconciliation. In response to this tragedy, there was bipartisan government action which included support for the affected and enhanced funding for antiterrorism efforts, aiding in the prevention of future attacks of a similar nature.

Explanation:

Coefficients are the number present in front of an atom or molecule in a chemical reaction.

For example, [tex]2Na + Cl_{2} \rightarrow 2NaCl[/tex]

In this reaction 2 in front of Na in reactant side shows 2 moles of sodium atoms are participating. Whereas 2 in front of NaCl in product side shows that 2 moles of sodium chloride is formed.

Therefore, we can conclude that coefficients in a balanced chemical equation tell you the moles of each substance involved in the reaction.

This is as straightforward as it gets. If however you need to determine how much of each product is produced, then the balanced equation is a must.

Usually, gasoline is expressed as octane in combustion reactions, which means that the balanced equation for its combustion is

2C8H18+25O2→16CO2+18H2O

But, like I've said, for the combined mass of the products all you really need to know is the combined mass of the reactants.

Addendum

Let's say you want to know exactly how much of each compound is formed. In this case, you must check for a limiting reagent. The number of moles of octane is

21⋅103 g⋅1 mole octane114.0 g=184.2 moles

The number of moles of oxygen is

85⋅103 g⋅1 mole O232.0 g=2656 moles

According to the mole ratio between these two, each 2 moles of octane need 25 moles of oxygen, so

noxygen that reacts=noctane⋅252=2303 moles , which means that octane is the limiting reagent. The actual mass of oxygen that reacts is

2303 moles⋅32.0 g1 mole=73.7 kg

This means that the combined mass of the produced water and carbond dioxide is actually

21 kg+73.7 kg=94.7 kg

85 kg−73.7 kg=11.3 kg of oxygen will not react. If you want to count this oxygen as well, the total combined mass of the products will again be 106 kg .

In complete and ideal combustion of gasoline using the principle of conservation of mass, the total combined mass of carbon dioxide and water produced when a gasoline tank holding 21 kg of gasoline burns consuming 84 kg of oxygen is 105 kg.

The subject of your question is based on the principle of conservation of mass, a fundamental concept in chemistry. The principle of conservation of mass states that the total mass of the reactants (the starting materials in a chemical reaction) is equal to the total mass of the products (the substances formed by the reaction). Hence, in the combustion (burning) of gasoline, the total combined mass of carbon dioxide and water that is produced would be equal to the sum of the masses of the gasoline and the oxygen consumed.

In your case, the total mass of gasoline and oxygen consumed is 21 kg (for gasoline) + 84 kg (for oxygen) = 105 kg. This means that given ideal condition and complete reaction, the total combined mass of carbon dioxide and water produced should be 105 kg.

Remember that this calculation assumes complete conversion of gasoline and oxygen into carbon dioxide and water, without production of other byproducts such as carbon monoxide and nitrogen oxides. Actual combustion processes may not be 100% efficient and may generate other byproducts.

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Answer:

D. They must have opposite spins.

Explanation:

Two electrons in the same atomic orbital have different spins or spin number. If one electron has +1/2 spin the other electron will have -1/2 spin. In other words if one electron is spinning in the clockwise direction the other electron will be spinning in the anticlockwise direction. Two electrons in the same atomic orbital have the same principal quantum number (n), azimuthal quantum number (l) and magnetic quantum number (m).

Answer: The correct answer is Option 3 and Option 4.

Explanation:

Redox reactions are termed as the reactions in which reduction and oxidation reactions occur simultaneously.

Reduction reactions are the ones where a substance gains electrons. The oxidation state of the substance gets reduced.

Oxidation reactions are the ones where a substance looses electrons. The oxidation state of the substance is increased.

Fro the given options:

Option 1: [tex]FeS(s)+2HCl(aq.)\rightarrow H_2S(g)+FeCl_2(g)[/tex]

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 2: [tex]AgNO_3(aq.)+NaCl(aq.)\rightarrow AgCl(s)+NaNO_3[/tex]

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 3: [tex]2C_3H_6(g)+9O_2(g)\rightarrow 6CO_2(g)+6H_2O(g)[/tex]

On reactant side:

Oxidation state of Carbon = +2

Oxidation state of Oxygen = 0

On product side:

Oxidation state of Carbon = +4

Oxidation state of Oxygen = -2

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of oxygen is getting reduced from 0 to -2. Thus, it is getting reduced.

Option 4: [tex]Fe_2O_3(s)+3CO(g)\rightarrow 2Fe(l)+3CO_2(g)[/tex]

On reactant side:

Oxidation state of Iron = +3

Oxidation state of Carbon = +2

On product side:

Oxidation state of Iron = 0

Oxidation state of Carbon = +4

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of iron is getting reduced from +3 to 0. Thus, it is getting reduced.

Hence, the correct answer is Option 3 and Option 4.

Mendeleev identified the periodic nature of elements' chemical properties when arranged by increasing atomic mass, leading to the creation of the periodic table.

Mendeleev noticed that certain similarities in the chemical properties of elements appeared at regular intervals when the elements were arranged in order of increasing atomic mass. This pattern is referred to as periodic, analogous to other phenomena that occur at regular intervals, such as the swing of a pendulum or the orbit of the moon around Earth. In the construction of his periodic table, Mendeleev even listed some elements out of atomic mass order so that they would be grouped with those that had similar chemical properties, such as tellurium (Te) being placed before iodine (I) based on properties rather than atomic mass.

Dimitri Mendeleev and Lothar Meyer independently recognized the periodic relationship among the elemental properties. While Meyer arranged elements by increasing atomic mass, Mendeleev's approach distinguished him by predicting undiscovered elements like gallium and germanium, which were later found and confirmed the utility of Mendeleev's table. This foresight helped solidify the significance of Mendeleev's work on the development of the periodic table.