Chemistry - A Molecular Science

Chapter 9 Reaction Energetics

38.

Draw a reaction diagram for a reaction

in which the activation energies of

the forward and reverse reactions are 20

and 40 kJ/mol, respectively. What

is

ΔH for the reaction? Draw the reaction diagram for the same reaction in

the presence of a catalyst.

39.

Write the equilibrium constant expression for each of the following reactions: a)

H

(g) + I 2

(g) 2

U

2HI(g)

b) HF(aq) + H

O(l) 2

U

H

O 3

1+(aq) + F

1-(aq)

c) CaCO

(s) 3

U

CaO(s) + CO

(g) 2

d) 2NO

1- 3

(aq) + 8H

1+(aq) + 6Br

1-(aq)

U

2NO(g) + 4H

O(l) + 3Br 2

(aq) 2

40.

Write the equilibrium constant expression for each of the following reactions: a)

2H

(g) + O 2

(g) 2

U

2H

O(g) 2

b) H

SO 2

(aq) + 2NH 3

(aq) 3

U

SO

2- 3

(aq) + 2NH

1+ 4

(aq)

c) 2Ag

1+(aq) + CrO

2- 4

(aq)

U

Ag

CrO 2

(s) 4

d) 3Fe(s) + 2Au

3+(aq)

U

2Au(s) + 3Fe

2+(aq)

41.

The following pressures were measured in an equilibrium mixture at some temperature: P

NH

= 0.20 atm; P 3

= 0.080 atm and PH 2

= 0.16 atm. What is N 2

the value of the equilibrium

constant for the reaction 2NH

(g) 3

U

N

(g) + 2

3H

(g) at this temperature? 2

42.

An equilibrium mixture at 25

oC consists of an aqueous solution that is

0.010 M in Pb

2+ ions and 0.041 M in Cl

1- ions above 0.010 mol of solid

PbCl

. What is the value of the equilib 2

rium constant for the following

reaction: PbCl

(s) 2

U

Pb

2+(aq) + 2Cl

1-(aq)?

43.

What is the pressure of I

in equilibrium with 0.065 atm of H 2

and 0.021 2

atm of HI at a temperature where K = 6.7 for the reaction H

(g) + I 2

(g) 2

U

2HI(g)?

44.

Given that K = 7.2x10

-4 for HF(aq) + H

O(l) 2

U

1- F

(aq) + H

O 3

1+(aq),

determine the molar concentration of F

1- ion in equilibrium with [HF] =

0.10 M and [H

O 3

1+] = 5.0

x^10

-4 M.

45.

Consider the following

thermochemical reaction,

N

(g) + 3H 2

(g) 2

U

2NH

(g) 3

HΔ

o = -91.8 kJ/mol

a) How much heat is released when 1.0 g of NH

is formed? 3

b) How much heat is released when 1.0 mol of H

reacts? 2

c) How much heat must be absorbed to form 2.0 g of N

? 2

d) How many moles of ammonia are fo

rmed in a reaction that produces

200 kJ of heat?

46.

Consider the combustion of methane,

CH

(g) + 2O 4

(g) 2

U

CO

(g) + 2H 2

O(l) 2

HΔ

o = -882 kJ/mol

a) How many grams of methane must burn to produce 1,000 kJ of heat? b) How much heat is released when 4.0 g of O

react? 2

c) How much heat is released when 1.5 mol of CO

is formed? 2

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