Chapter 7 SmartBook - CHM 104

Given the equilibrium concentrations, [H2] = 0.55 M and [CO] = 1.2 M, what is the equilibrium concentration of CH3OH? 2H2(g) + CO(g) ⇌ CH3OH(g), Keq = 1.6 × 10-2

5.8 × 10-3 M

Bond ____ always requires an input of energy, whereas bond ____ involves a release of energy.

breaking ; formation

The spontaneity of a chemical reaction depends on the relative magnitude of the ____ and ____ values

enthalpy ; entropy

The measure of the randomness or disorder of a chemical system is called ____

entropy

If a chemical system at ____ is stressed, the system will shift the equilibrium composition to relieve the ____

equilibrium ; stress

When a chlorine-chlorine bond is formed, 58 kcal of energy is ______. To break the same bond, 58 kcal of energy is ______.

released; absorbed

Select all that apply Which of the following options correctly describe a dynamic chemical equilibrium?

- Product is being consumed and formed at the same rate. - The rate of depletion of reactants is equal to the rate of depletion of products. - The forward and reverse reactions continue indefinitely.

0.100 moles of an acid is mixed with 0.100 moles of a base in a calorimeter and the temperature of 85.0 g of the resulting solution increases from 23.3°C to 34.5°C. If the specific heat of the solution is 1.00 cal/g °C, what is the quantity of energy released or absorbed by the reaction?

952 cal released

Match each term to the correct description concerning the equation used in calorimetry: Q = ms × ΔTs × SHs

- Q = The quantity of heat absorbed or released by the reaction - ms = The mass of the solution in the calorimeter - ΔTs = The change in temperature of the solution - SHs = The specific heat of the solution

Match each term to the correct unit concerning the equation used in calorimetry: Q = ms × ΔTs × SHs

- Q = cal - ms = g - ΔTs = °C - SHs = cal/g x °C

Select all that apply Which of the following processes are associated with an increase of entropy?

- Sublimation - Vaporization - Expansion of a gas into an evacuated chamber - Melting

Match each description of entropy to the correct symbol or terms.

- Low entropy = A well-organized system - High entropy = A random or disordered system - S = The symbol used to represent the entropy of a substance

1. A Br—Br bond is broken. 2. A Br—Br bond is formed.

1. endothermic 2. exothermic

Match the given equilibrium constant, Keq, with its equilibrium's position. Instructions

- Neither side is greatly favored = 68 - Favors the products = 3.2 × 10^6 - Favors the reactants = 8.1 × 10^−4

Match each term to the correct description when describing changes in energy. 1. system = 2. surroundings = 3. change in energy =

1. the process under study 2. everything in the universe other than the process under study 3. energy absorbed or released

Select all that apply Which of the following values for Keq indicate that mostly products are present at equilibrium?

3.4 × 10^4 1.5 × 10^5

Select all that apply Which of the following options represent(s) an exothermic reaction?

- AB + CD → AD + BC + heat - The reaction of 1 mole of CH4(g) with 1 mole of Cl2(g) releases 26.4 kcal of heat.

Select all that apply If you want to shift a chemical equilibrium to the left by manipulating concentration, which of the following will give the desired result?

- Add product - Remove reactant

Select all that apply Select all the statements that correctly describe the equilibrium constant and the equilibrium constant expression.

- An equilibrium constant expression is written based on a balanced chemical equation. - Only the concentrations of gases and substances in solution are shown in an equilibrium constant expression. - Each chemical reaction has a unique equilibrium constant value.

Select all that apply What is an activated complex?

- An extremely unstable state in a chemical reaction, formed in the process of going from reactants to products - A state of a chemical reaction that requires energy to form - A short-lived group of atoms structured in such a way that it quickly and easily breaks apart

Select all that apply Which of the following options correctly describe the influence of molecular shape and orientation on reaction rate?

- Both size and shape of a reactant molecule influence the rate of reaction. - Product is only formed as a result of molecular collisions that have the correct collision orientation.

Match all terms relating to chemical kinetics to the correct description.

- Chemical kinetics = The study of the speed of chemical reactions - Reaction rate = The speed of a chemical reaction - Reaction mechanism = A step-by-step description of how reactants become products

Match each type of reaction to the correct description.

- Complete reactions = All reactants have been converted to products - Equilibrium reactions = measurable quantities of reactants and products remain after no further obvious change is taking place.

Match each process to the correct change in entropy associated with it.

- Condensation = Decrease in entropy - Vaporization = Increase in entropy - Increase in entropy = Decomposition of a liquid to form gaseous molecules - Decrease in entropy = Separation of a gaseous mixture into individual components

Select all that apply Which of the following statements correctly describe energy changes in chemical reactions?

- Energy that is exchanged between the system and the surroundings in the form of heat can be measured through changes in temperature. - Changes in energy as a chemical reaction occurs can be measured. - Any energy that is lost from the system is gained by the surroundings.

Match each sentence beginning to the correct sentence ending to describe what occurs in calorimetry.

- For an exothermic reaction = heat released by the reaction is absorbed by the surrounding solution. - For an endothermic reaction = the reactants absorb heat from the solution. - The temperature of the solution increases = in the case of an exothermic reaction. - The temperature of the solution decreases = in the case of an endothermic reaction.

Select all that apply Which of the following options correctly describe a change in free energy?

- Free energy change is the combined contribution of the enthalpy and entropy values for a chemical reaction. - Free energy change is the ultimate predictor of reaction spontaneity.

Match each species in the following equilibrium constant expression to the correct unit(s). Keq = [Z]^c / [X]^a[Y]^b

- Keq = Unitless - [X], [Y], [Z] = mole/L

A calorimeter containing a solution initially with a temperature of 23.3°C is used to carry out different chemical reactions. Match the final temperature of each reaction mixture in the calorimeter to the type of reaction or heat transfer that took place.

- Tf = 30.5°C = The heat is released by the reaction. - Tf = 19.2°C = The heat is absorbed by the reaction. - The reaction is exothermic = Tf = 32.1°C - The reaction is endothermic = Tf = 20.5°C

Select all that apply Which of the following options correctly describes enthalpy?

- The change in enthalpy is represented by the symbol ΔH. - The change in enthalpy is the energy difference between the products and reactants of a chemical reaction. - Enthalpy is a term used to represent heat.

Select all that apply Which of the following options correctly describe calorimetry?

- The device used to measure heat changes in a system is called a calorimeter. - Calorimetry involves the measurement of the change in temperature of a quantity of water or solution that is in contact with a reaction. - Calorimetry is the measurement of heat energy changes in a chemical reaction.

Select all that apply How does the structure of the reacting species affect reaction rate?

- The magnitude of the activation energy is related to bond strength. - Bond strength plays a role in determining reaction rates.

Select all that apply What is the activation energy (Ea) for a chemical reaction?

- The minimum amount of energy required to initiate a chemical reaction - The difference between the energy of reactants and that of the activated complex

Select all that apply Thermodynamics includes the study of ____

- heat - work - energy

Match the effect of increasing or decreasing pressure to the direction the equilibrium shifts to relieve the stress in accordance with LeChatelier's principle.

- increase pressure = The equilibrium shifts toward the side of the reaction that has fewer moles of gas. - decrease pressure = The equilibrium shifts toward the side of the reaction that has more moles of gas.

Select all that apply When the energy required to break bonds is ______ the energy released when forming bonds in a chemical reaction, the reaction is characterized as ______

- less than; exothermic - greater than, endothermic

Match the following words that complete the statement below regarding the effect of concentration on equilibrium: "Adding _____ will drive the equilibrium to the _____".

- reactant = right - product = left

Select all that apply According to LeChatelier's principle, a stress on a system at equilibrium can be created by ______.

- removing heat (lowering the temperature) - increasing the pressure of a gaseous reactant - adding more reactant or product - removing reactant or product

Select all that apply Reaction rate increases with increasing temperature because _____.

- the speed of reactant particles increases, which increases the likelihood of effective collisions - the average kinetic energy of the reacting particles increases

Select all that apply Thermodynamics may be applied to _____

- the study of energy, work, and heat for a chemical process - the calculation of the quantity of energy released or consumed in a physical change - the calculation of the quantity of heat obtained from a chemical reaction - the study of heat lost or gained when a substance changes phase

Select all that apply Reaction order is characterized or described by ______

- the symbol n - an exponent to which the molar concentration of a reactant is raised when relating reaction rate and reactant concentration

Select all that apply What factors favor a spontaneous chemical reaction?

- ΔSreaction > 0 - An increase in entropy - The chemical reaction is exothermic.

The equilibrium constant for the following reaction is 1.5 × 103. Match the equilibrium concentration of [A] to that of [A2]. 2A(g) ⇌ A2(g)

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Match each thermochemical equation to the correct description. 1. Exothermic reaction = 2. Endothermic reaction = 3. 55 kcal+A+B→C+D = 4. A + B → C + D + 55 kcal

1. A + B → C + D + heat 2. heat + A + B → C + D 3. Endothermic reaction 4. Exothermic reaction

Click and drag on elements in order List the steps to determine an equilibrium constant in the order that they are carried out. The first step belongs at the top of the list.

1. Carry out the reaction of interest until the concen

Match each type of reaction to the correct description. 1. Endothermic reaction = 2. Exothermic reaction = 3. Energy is a reactant and is required in the reaction = 4. Energy is a product and is released in the reaction =

1. Surroundings become colder as the reaction absorbs heat from the surroundings 2. Surroundings become warmer as the reaction releases heat to the surroundings 3. Endothermic reaction 4. Exothermic reaction

Match each type of reaction to the correct description concerning the following process: A—B + C—D → A—C + B—D 1. endothermic reaction = 2. exothermic reaction =

1. The energy required to break the bonds in the reactants is greater than the energy released from forming bonds in the products. 2. The energy required to break the bonds in the reactants is less than the energy released from forming bonds in the products.

Match each type of reaction to the correct definition. The reaction is defined as the system. 1. Exothermic reaction = 2. Endothermic reaction =

1. The reaction releases energy to the surroundings. 2. The reaction absorbs energy from the surroundings.

Select all that apply Which of the following stresses shifts the equilibrium to the left (more reactants)? Select all that apply. 2CO(g) + O2(g) ⇌ 2CO2(g)

Add more CO2 Remove O2

Select all that apply Which of the following changes made to the reaction below, will result in the formation of more product? Select all that apply. H2(g) + Cl2(g) ⇌ 2HCl(g)

Decrease [HCl] Increase [Cl2]

Select all that apply Which of the following reactions are endothermic?

H--O--H→ H--O dot + dot H H--Cl : → H dot + Cl :

The rate of the reaction A → products depends on the concentration of the reactant A. Which of the following correctly shows this mathematical relationship?

Rate ∝ concentration of A

The following equilibrium is exothermic: 2NO2(g) ⇌ N2O4(g) Match the shift in equilibrium with the change in temperature that it results from.

The equilibrium shifts left = The temperature is increased The equilibrium shifts right = The temperature is decreased.

Which of the following options correctly describe a dynamic equilibrium?

The rate of the forward process is exactly balanced by the rate of the reverse process.

Select all that apply An equilibrium reaction is found to shift to the right (driving toward the formation of additional products) upon decreasing the temperature of the reaction. Which of the following statements are true regarding the reaction?

The reverse reaction is endothermic. The forward reaction is exothermic.

A reaction is carried out and analyzed in order to determine the value for Keq. At what point should the reactant and product concentrations be measured for the calculation of Keq?

When the concentrations of both reactant and product become constant over time

The equilibrium constant, Keq, is equal to which of the following expressions given: aA + bB ⇌ cC + dD

[C]^c[D]^d / [A]^a[B]^b

A higher reactant concentration generally results in an increase in reaction rate because ______.

a larger number of effective collisions can occur

Reaction order is determined by ______.

a series of experiments

For an equilibrium reaction involving gases, when the pressure on the system ______, the equilibrium shifts in the direction that ______ the total moles of gas in order to decrease the pressure.

increases; decreases

In nature, both _____ and _____ equilibria are commonly observed.

physical; chemical

The change in enthalpy is the energy difference between the ____ and ____ of a chemical reaction and is symbolized as ΔH.

products ; reactants

The equilibrium constant, Keq, is the ratio of the concentrations of the ____ over the concentrations of the ____ and is a characteristic value of a reaction at a given ____

products ; reactants ; temperature

In most cases, the rate of the reaction is _____ the concentration of the reactant(s) when all other factors affecting rate are held constant.

proportional to

Chemical kinetics is the study of the _____ of chemical reactions and gives an indication of the _____ of a reaction.

rate ; mechanism

Free energy change is symbolized by which of the following?

ΔG