Question 1

The formation of rust (Fe₂O₃) on an exposed piece of metal typically takes several months.Which of the following statements is NOT a reasonable assumption about this chemical reaction? 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

Accepted Answer

The formation of rust involves the reaction between iron and oxygen, which has a high activation energy. Therefore, it is not a reasonable assumption to say that the reaction has a low activation energy. The other options are reasonable assumptions based on what is known about the reaction.

Question 2

A candy sample is completely combusted in a bomb calorimeter.The calorimeter contains 982 g of water, and the measured temperature increase is 2.62°C.What is the fuel value of the candy sample in nutritional Calories? [SHw = 1.00 cal/g•°C]

Accepted Answer

C

Question 3

What is the name and symbol of the thermodynamic quantity that represents the heat absorbed or liberated in a chemical reaction at constant pressure?

Accepted Answer

Enthalpy Change, represented by the symbol ∆H, is the thermodynamic quantity that represents the heat absorbed or liberated in a chemical reaction at constant pressure.

Question 4

What thermodynamic quantity is the ultimate predictor of reaction spontaneity?

Accepted Answer

Free Energy Change (∆G) is the ultimate predictor of reaction spontaneity, as it combines both the enthalpy change (∆H) and entropy change (∆S) of the system. A negative ∆G indicates that the reaction is spontaneous, while a positive ∆G indicates that the reaction is non-spontaneous. Therefore, ∆G is a better predictor than ∆H or ∆S alone.

Question 5

The amount of heat necessary to raise 1 gram of a substance by 1 degree Celsius is known as which of the following?

Accepted Answer

The specific heat of a substance is the amount of heat energy required to raise the temperature of 1 gram of that substance by 1 degree Celsius. Enthalpy is the total heat content of a system, activation energy is the energy required to start a chemical reaction, heat of vaporization is the amount of heat energy required to vaporize a substance, and free energy is the energy provided by a system that can be used to do work.

Question 6

Which of the following statements concerning the reaction below is FALSE? 2HgO(s) → 2Hg(l) + O₂(g) ∆H = 182 kJ

Accepted Answer

The reaction is endothermic, meaning it absorbs energy (182 kJ) from the surroundings, indicating that the energy of the products is greater than the energy of the reactants, not the other way around. This is because energy is absorbed to break the bonds in HgO, resulting in a net gain of energy in the system.

Question 7

Which statement concerning energy changes in chemical reactions is FALSE?

Accepted Answer

In an exothermic reaction, the products have a lower energy than the reactants, not higher. This is because energy is released to the surroundings, indicating that the reactants had more stored energy that was then released during the reaction.

Question 8

Which of the following is the equilibrium constant expression for the reaction? 2NO(g) + O₂(g) → 2NO₂(g)

Accepted Answer

The answer of Which of the following is the equilibrium...

Question 9

Consider the decomposition of calcium carbonate shown below.Which of the following statements correctly describes this reaction as it occurs in a test tube? CaCO₃(s) + 42.5 kcal → CaO(s) + CO₂(g)

Accepted Answer

The reaction is endothermic (heat is absorbed) as indicated by the positive enthalpy change (42.5 kcal). Therefore, the test tube would feel cold as the reaction absorbs heat from the surroundings.

Question 10

For the reaction shown below, Keq=2×10¹¹.Which of the following statements concerning this system at equilibrium is true?

Accepted Answer

The answer of For the reaction shown below, Keq=2×10¹¹.Which of...

Question 11

What is the term used to describe the energy barrier the reactants must overcome in order to form products in a chemical reaction?

Accepted Answer

The term used to describe the energy barrier the reactants must overcome in order to form products in a chemical reaction is activation energy. This is the minimum amount of energy required for a reaction to occur.

Question 12

The rate of a chemical reaction increases with an increase in concentration of one or more of the reactants.This is best explained by which of the following statements?

Accepted Answer

Increasing the concentration of reactants increases the likelihood of effective collisions between molecules, which in turn increases the rate of reaction. Therefore, the statement that best explains this is option D - The increased concentration of the reactants increases the frequency of effective collisions.

Question 13

A carbohydrate sample weighing 0.235 g was found to have a fuel value of 3.84 kJ.What is the fuel value of one gram of this carbohydrate, in nutritional Calories?

Accepted Answer

The fuel value of one gram of this carbohydrate is 3.84 kJ / 0.235 g = 16.3 kJ/g. Since 1 nutritional Calorie is equal to 4.184 kJ, the fuel value of one gram of this carbohydrate is 16.3 kJ/g * (1 Cal / 4.184 kJ) = 3.91 Cal/g.

Question 14

Which of the following is FALSE about the energy diagram shown?

Accepted Answer

The answer of Which of the following is FALSE about...

Question 15

Which statement concerning energy changes in chemical reactions is FALSE?

Accepted Answer

The overall change in enthalpy (∆H) for a reaction is determined by the difference in energy between the reactants and the products, not between the products and the activated complex.

Question 16

Which statement concerning a reversible reaction at equilibrium is FALSE?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal, not necessarily the concentrations of products and reactants.

Question 17

Ammonia is synthesized industrially by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the reaction equation below.What effect would removing the iron catalyst have on this reaction?

Accepted Answer

The answer of Ammonia is synthesized industrially by the reaction...

Question 18

What instrument is used for measuring the heat energy absorbed or released in a chemical reaction?

Accepted Answer

A calorimeter is specifically designed for measuring the heat energy changes in chemical reactions, while a thermometer measures temperature changes. A thermos is designed for keeping substances at a constant temperature, and a balance or scale is used for measuring mass.

Question 19

How many small calories are equivalent to one nutritional Calorie?

Accepted Answer

One nutritional Calorie (with a capital "C"), also known as a kilocalorie, is equivalent to 1,000 small calories (with a lowercase "c").

Question 20

A reversible reaction is said to have reached equilibrium when which of the following conditions is established?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions become equal. This means that the concentrations of reactants and products no longer change with time, indicating that the reaction has achieved a steady state. A reversible reaction can still occur at equilibrium, but it occurs at an equal rate to the reverse reaction. The forward reaction does not necessarily diminish to zero, and the concentrations of reactants and products do not necessarily become equal. The reactants may or may not be completely consumed, depending on the stoichiometry of the reaction.

Quiz 7: Energy, Rate and Equilibrium

The formation of rust (Fe2O3) on an exposed piece of metal typically takes several months.Which of the following statements is NOT a reasonable assumption about this chemical reaction? 4Fe(s) + 3O2(g) → 2Fe2O3(s)

A candy sample is completely combusted in a bomb calorimeter.The calorimeter contains 982 g of water, and the measured temperature increase is 2.62°C.What is the fuel value of the candy sample in nutritional Calories? [SHw = 1.00 cal/g•°C]

What is the name and symbol of the thermodynamic quantity that represents the heat absorbed or liberated in a chemical reaction at constant pressure?

What thermodynamic quantity is the ultimate predictor of reaction spontaneity?

The amount of heat necessary to raise 1 gram of a substance by 1 degree Celsius is known as which of the following?

Which of the following statements concerning the reaction below is FALSE? 2HgO(s) → 2Hg(l) + O2(g) ∆H = 182 kJ

Which statement concerning energy changes in chemical reactions is FALSE?

Which of the following is the equilibrium constant expression for the reaction? 2NO(g) + O2(g) → 2NO2(g)

Consider the decomposition of calcium carbonate shown below.Which of the following statements correctly describes this reaction as it occurs in a test tube? CaCO3(s) + 42.5 kcal → CaO(s) + CO2(g)

For the reaction shown below, Keq=2×1011.Which of the following statements concerning this system at equilibrium is true?

What is the term used to describe the energy barrier the reactants must overcome in order to form products in a chemical reaction?

The rate of a chemical reaction increases with an increase in concentration of one or more of the reactants.This is best explained by which of the following statements?

A carbohydrate sample weighing 0.235 g was found to have a fuel value of 3.84 kJ.What is the fuel value of one gram of this carbohydrate, in nutritional Calories?

Which of the following is FALSE about the energy diagram shown?

Which statement concerning energy changes in chemical reactions is FALSE?

Which statement concerning a reversible reaction at equilibrium is FALSE?

Ammonia is synthesized industrially by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the reaction equation below.What effect would removing the iron catalyst have on this reaction?

What instrument is used for measuring the heat energy absorbed or released in a chemical reaction?

How many small calories are equivalent to one nutritional Calorie?

A reversible reaction is said to have reached equilibrium when which of the following conditions is established?

The formation of rust (Fe₂O₃) on an exposed piece of metal typically takes several months.Which of the following statements is NOT a reasonable assumption about this chemical reaction? 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

Which of the following statements concerning the reaction below is FALSE? 2HgO(s) → 2Hg(l) + O₂(g) ∆H = 182 kJ

Which of the following is the equilibrium constant expression for the reaction? 2NO(g) + O₂(g) → 2NO₂(g)

Consider the decomposition of calcium carbonate shown below.Which of the following statements correctly describes this reaction as it occurs in a test tube? CaCO₃(s) + 42.5 kcal → CaO(s) + CO₂(g)

For the reaction shown below, Keq=2×10¹¹.Which of the following statements concerning this system at equilibrium is true?