smartbooks- chapter 17

For the reaction H2C2O4 (aq) ⇌ 2H+ (aq) + C2O42- (aq), Kc = 3.8 × 10-6. Calculate the value of Kc for the reaction 5H2C2O4 (aq) ⇌ 10H+ (aq) + 5C2O42- (aq). Multiple choice question.

7.9x 10^-28

Given the reaction 2NO2 (g) ⇌ 2NO (g) + O2 (g); K = 1.1 x 10-5, what is the value of K for the reaction 2NO (g) + O2 (g) ⇌ 2NO2 (g)?

9.1 x 10^4

the equilibrium constant is a special value of the rxn ____ that occurs when reactant and product concentrations are at their ____ values

quotient equilibrium

When Q < K, the reaction will proceed so that the concentrations of the _____ decrease and the concentrations of the _____ increase

reactants products

describe the equilibrium constant K

-K = kfwd/krev for a system at equilibrium -K expresses a particular ratio of equilibrium concentrations of products and reactants -the value of K is characteristic of a particular equilibrium system

0.45 mol PCl5 (g) is placed in a sealed 2.0-L container and reacts according to the equation: PCl5 (g) ⇌ PCl3 (g) + Cl2 (g). If [Cl2] = 0.10 M at equilibrium, select all the options that correctly reflect the steps required to calculate Kc.

-Kc = (.10)(.10) / (0.13) -initial [PCl5] - 0.23 M -at equilibrium, [PCl3] = 0.10M

For the reaction CO (g) + Cl2 (g) ⇌ COCl2 (g), Kp at 1000 K = 3.9 × 10-2. Which of the following options correctly reflect the steps required to calculate Kc at 1000 K? Select all that apply. Multiple select question.

-Kc = (3.9x 10^-2)(0.0821 x 1000)^1 = 3.2 -∆ngas - -1

which of the following correctly describe reaction quotient Q

-Q = K only at equilibrium -the expression for Q is the same as the expression for K -Q expresses a particular ratio of products and reactants at any time during a rxn

Select all the options that correctly reflect the steps required to determine the direction in which the following reaction will proceed at the given concentrations 2NO2Cl (g) ⇌ 2NO2 (g) + Cl2 (g), where Kc = 3.21 × 10-4 if [NO2Cl] = 0.012 M, [NO2] = 0.018 M, and [Cl2] = 0.026 M.

-Qc = 5.9x10^-2 -since Qc > Kc, the reaction will proceed towards the reactants

Which of the following options correctly reflect the equation relating KP and Kc for a given reaction?

-T is the temperature in kelvin -∆ngas is determined from the coefficients of the balancing equation -R - 0.0821 atm*L/mol*K

0.20 mol of N2 (g) and 0.15 mol of O2 (g) are placed in a 1-L container and allowed to react according to the equation N2 (g) + O2 (g) ⇌ 2NO (g), Kc = 4.10 x 10-4. Place the following steps to solve for [NO] at equilibrium in the correct order, starting with the first step at the top of the list.

-assume that hte change in [N2] = x -Kc = 4.0x10^-4 -asssume that x is small so that -solve for x then -check that x < 5% of both 0.20 and 0.15

Which of the following statements correctly describe how the addition of a catalyst will affect a system at equilibrium? Select all that apply.

-catalyst does not change K -equil is unaffected

law of mass action states that:

-equilibrium can be reached from any direction (by beginning with mixture of reactants, or products, or both) -a chemical system reaches a state where the concentrations of reactants and products is a constant ratio

1.9 moles of HI are added to an evacuated, sealed 10.-L reaction vessel and allowed to decompose according to the following reaction: H2 (g) +I2 (g) ⇌ 2 HI(g); Kc = 1.26 × 10−3H2 (g) + I2 (g) ⇌ 2 HI (g); Kc = 1.26 × 10-3 Which of the following options correctly reflect how to calculate [H2]H2 at equilibrium? Select all that apply. Multiple select question.

-if the change in [H2] = +x, then at equilibrium [I2] = x -the initial [HI] = 0.19M -Kc = 1.26x10^-3 = (0.19 - 2x)^2 / x^2

as a rxn proceeds, the value of Q

-increases or decreases as necessary until it reaches the value of K

which of the following correctly describe a chemical system at equilibrium?

-no longer a change in concentration of reactants and products over time -the forward and reverse rxns occur at equal rates

For the following reaction, what will be observed if the volume is increased at constant temperature? Select all that apply. 2NO2 (g) ⇌ 2NO (g) + O2 (g)

-the concentrations of all species will decrease -eq pos will shift toward the products

0.20 mol of NO (g) is placed in a 1-L container with 0.15 mol of Br2 (g). These will react according to the balanced equation: 2NOBr (g) ⇌ 2NO (g) + Br2 (g). Given that [NOBr] = 0.18 M at equilibrium, select all the options that correctly describe the steps required to calculate Kc for the reaction.

-the initial [NOBr] = 0M -if the change in [Br₂] = -x then the change in [NOBr] = +2x -x = 0.18/2 = 0.09

Consider the equilibrium system C (s) + H2O (g) ⇌ CO (g) + H2 (g); ΔHorxn = 131 kJ.

-value of Kc will decrease -equil will shift toward reactants -equil concentrations of H2O will increase

Which of the following statements correctly describe how an equilibrium system containing gases will respond to changes in volume and/or pressure if the temperature remains unchanged? Select all that apply.

-volume is decreased, rxn shifts in dir that produces fewer moles gas -if inert gas added, no effect on equil position -if total number of moles of gas in prod and reactants is the same, a change in volume will not affect equil position

Calculate the equilibrium concentration of PCl3 for the equilibrium system represented below. PCl5 (g) ⇌ PCl3 (g) + Cl2 (g); Kc= 62; [PCl5] = 0.00582 M, and [Cl2] = 0.731 M.

0.49M

Consider the equilibrium system 2NO2 (g) ⇌ 2NO (g) + O2 (g); K1 = 1.1 x 10-5. What is the value of K for the reaction 6NO2 (g) ⇌ 6NO (g) + 3O2 (g)?

1.3x10^-15

K and Q descriptions

K -> expresses a particular ratio of product and reactant conc for a rxn at equilibrium Q -> expresses a particular ratio of product and reactant conc for a rxn at any time

0.50 mol of SO3 (g) is placed in a sealed 1-L container at 700°C and reacts according to the equation: 2SO3 (g) ⇌ 2SO2 (g) + O2 (g). If [O2] at equilibrium = 0.15 M, which of the following gives the correct calculation for Kc?

Kc = [(0.15)(0.30)^2]/(0.20^2) = 0.34

A sample of solid C is placed in a sealed reaction vessel containing 2.0 atm H2 (g) and allowed to react according to the equation C (s) + 2H2 (g) ⇌ CH4 (g). At equilibrium the partial pressure of CH4 = 0.39 atm. Calculate Kp for the reaction. Multiple choice question.

Kp = 0.26

In a given experiment, 0.10 atm of each component in the following reaction is placed in a sealed container. In which direction will the reaction proceed? 2NOBr (g) ⇌ 2NO (g) + Br2 (g) where KP = 60.6 at 100°C

The reaction proceeds toward the products.

the law of mass action reflects the observation that an equilibrium state is reached by a chemical system regardless of the ____ concentrations of reacting substances. in other words, a chemical system can reach equilibrium either from the reactants or from the ______

initial products