The equilibrium constant kc is 9.8 x 10 5

Chemistry ICE Table HW

Chem 112-002 Equilibrium HMWK SP18 Name _____________________ BSU ID _____________ 13 points DUE Wednesday, March 7, 2018 BY 5 PM Show all work. No credit given if no work shown.

1. (1 pts) Fill in the table for the equilibrium

kforward

A (g) B (g)

kbackward Answer “yes” in column 2 if the statement in column 1 must be true at equilibrium, answer “no” if it is not true (or not

necessarily true.)

(1) Condition (2) yes or no (3) explain your “yes” or “no” in column 2

kforward = kbackward

[A] = [B]

rateforward = ratebackward

PA = PB

no reaction is occurring

2. In the ICE table below, a balanced chemical equation is shown. Initial amounts are given for the reactants,

and a final observed concentration for the product. The volume of the vessel is 1.0 L

(a) (0.5 pts) Show by calculation if there is enough P4 (s) to permit that amount of the product PH3 to form,

with some P4(s) left over. (P4 has to be present in excess for the equilibirum to be established.)

(b) (0.5 pts) Complete this ICE table.

Balanced equation: 6 H2 (g) + P4 (s) ⇄ 4 PH3 (g)

Initial conc (or amount)

3.86 x 10−3 M 0.500 g 6.05 x 10−5 M

change in conc

.

Equilibrium

concentration

1.27 x 10−4 M

(c) (0.5 pt) Calculate Keq for the reaction at this temperature. (Hint: notice the phase of each participant.)

Keq =

3.(a) (1 pt) Initial concentrations were controlled as shown. Only the NO2 could be measured at equilibrium, and its

equilibrium concentration is shown. Complete this ICE table with numbers. You will not need to use an "x".

The overall reaction is 2 N2O5 (g) ⇄ 4 NO2 (g) + O2 (g) Initial conc

0.0500 M N2O5 0.0300 M NO2 0.0100 M O2

Change in conc Equilibrium conc. 0.0050

(b) (0.5 pt) Using the equilibrium values in your table, calculate the equilibrium constant Kc for this reaction.

4. (0.5 pt) Hydrogen and carbon monoxide react to give formaldehyde, under certain conditions.

H2 (g) + CO (g)  HCHO (g)

The mechanism proposed for this reaction is:

step 1. fast, reversible H2  2 H

step 2. slow H + CO  HCO

step 3. fast H + HCO  HCHO

Which of the following rate laws is consistent with this mechanism (and would be allowed)? EXPLAIN THE

REASONS FOR YOUR CHOICE. (No credit will be given if there is no explanation.) rate = ?

a) k[H2] 2

1

[CO] b) k[H2]2[CO] c) k[H2][CO]

d) k[H2][ CO]2 e) k[H][HCO]

(1 pt) Explanation:

5. (a) (0.4 pt) Write the equilibrium constant expression for this reaction:

8 H2 (g) + 3 N2 (g) N2H4 (g) + 4 NH3 (g)

Keq (a) = ?

(b) (0.3 pt) Write the equilibrium constant expression for the reverse reaction of part (a):

N2H4 (g) + 4 NH3 (g) 8 H2 (g) + 3 N2 (g)

Keq (b) = ?

(c) (0.3 pt) Write the mathematical relationship between the two Keq's in parts (a) and (b), as

Keq, (b) = (what function of Keq, (a)?)

(d) (0.3 pts) Re-write the chemical equation in part a, multiplying all coefficients by 2. What is the

new Keq (d)? What is the relationship between this new Keq (d) and the original Keq (a)?

6. (1 pts) (a) Show by calculation if the following gas phase reaction is at equilibrium, with the molar

concentration conditions stated under each participant. (Hint: Q, reaction quotient).

For this temperature, Keq = 1.45 x 104

4 NH3 + 5 O2  4 NO + 6 H2O

Instantaneous

concentrations, M: 5.4 x 10−4 4.5 x 10−5 2.3 x 10−5 9.7 x 10−3

(b) (0.5 pt) Based on your calculation in part (a) what will be observed over time, in the reaction vessel?

Circle one: more NO will form more NH3 will form no change

7. (a) (0.9 pts) The balanced equation for the acid dissociation of acetic acid is given below. Make an "ICE" table showing the initial concentrations, change in concentration and equilibrium concentrations of the three chemical species

in the reaction. Initial concentration of the acetic acid is 0.0575 M, Ka, acetic acid = 1.75 x 10−5

CH3COOH (aq) ⇄ CH3COO (aq) + H+ (aq) Initial:

Change:

Equilibrium:

(b) (0.6 pt) Use the data in the "ICE" table and the Ka stated in the problem to calculate the equilibrium value of [H+].

[H+]=

8. (1 pt) Ammonium carbamate NH4CO2NH2 decomposes as shown below

NH4CO2NH2 (s) ⇄ 2 NH3 (g) + CO2 (g) Starting with only the solid, it is found that at 40 oC the total gas pressure (NH3 and CO2) is 0.363 atm.

Calculate the equilibrium constant Kp. (Hint: ICE table)

Kp =

9. (1.2 pt) At a certain temperature the following reactions have the Kc constants shown;

⇄ (i) S (s) + O2 (g) ⇄ SO2 (g) Kc, i = 4.2 x 1052

(ii) 2 S (s) + 3 O2 (g) ⇄ 2 SO3 (g) Kc, ii = 9.8 x 10128 Calculate the equilibrium constant Kc for the following reaction at the same temperature.

2 SO2 (g) + O2 (g) ⇄ 2 SO3 (g) Kc = ????

Kc =

2 H2 (g) + S2 (g) Kc = 1.67 x 10 7 10. (1 pt) Consider the reaction: 2 H2S (g)

A reaction mixture initially contains [H2S] = 0.010 M, and none of the two products. Calculate the

equilibrium concentrations of H2 and S2. (hint: ICE table)

[H2 ] =

[S2] =