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# Chemistry Reactions

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Find the standard electrode potential, E°, and DG° for the following reaction:

4HIO3(aq) --> I2(s) + 2H2O + 5O2(g)

Is the reaction spontaneous? Can iodic acid exist?

Hint: HIO3 is ionized in water.

https://brainmass.com/chemistry/electrochemical-potentials/chemistry-reactions-standard-electrode-potential-133873

#### Solution Preview

4HIO3(aq) --> 2 I2(s) + 2H2O + 5O2(g)

First, we look up the half-reactions:

IO3- + 6H+ + 5e- --> 1/2 I2 + 3H2O E° = 1.195 V

O2 + 4H+ + 4e- --> 2 H2O E° = 1.229 V

Now, we must reverse the second equation and change the sign of E°.

2 H2O --> O2 + 4H+ + 4e- E° = -1.229 V

Next, we must make sure that the electrons balance. To do this, we must multiple the first equation by 4 and the second equation by 5. In total, there will be a redox reaction involving 20 electrons.

4 IO3- + 24 H+ + 20e- --> 2 I2 + 12 H2O E° = 1.195 V
10 H2O --> 5 O2 + 20H+ + 20e- ...

#### Solution Summary

The following posting helps find the standard electrode potential, E°, and DG° for a reaction. Step by step calculations are given.

\$2.19

## General Chemistry

1. 4CuO(s) + CH4(g) CO2(g) + 4Cu(s) + 2H2O(g)
The value of Kc for this reaction is 1.10 at 25.0°C. What is the
value of Kp for this reaction? (R = 0.0821 L-atm/K-mol)

a. 4.63
b. 26.9
c. 658
d. 37.2
e. 1.52 x 10-3

2. At a certain temperature, a flask at equilibrium contains 0.0551 M
HCl, 0.112 M Cl2, and 0.105 M H2. What is the value of Kc for the
equilibrium: 2 HCl(g) &#8594; Cl2(g) + H2(g)?

a. 3.87
b. 0.258
c. 11.0
d. 1.63 x 10-5
e. 0.213

3. Consider the following incomplete table of data for the equilibrium
between dinitrogen tetroxide and nitrogen dioxide.

Exp # Equilibrium N2O4 Concentr Equilibrium NO2 Concentration
1 0.00140 M 0.0172 M
2 0.00452 ?
3 0.00280 0.0243

From the information in the table, determine the value of the
missing NO2 concentration at equilibrium.

a. 0.0309
b. 0.0486
c. 9.54 x 10-4
d. 0.115
e. 0.0814

3. Consider the gaseous equilibrium: 2 A &#8594; 2 B + C
Determine the value of the missing B concentration at equilibrium.

Exp# [A] at equilibrium [B] at equilibrium [C] at equilibrium
1 0.10 M 0.15 M 0.20 M
2 0.20 0.50 0.072
3 0.35 ? 0.15

a. 0.20
b. 0.35
c. 0.61
d. 0.40
e. 0.37

4. The expression for Kc for the reaction below is _______________.
NiCO3(s) + 2H+(aq) Ni2+(aq) + CO2(g) + H2O(l)

a. [CO2]
b. [NiCO3]/[Ni2+]
c. [Ni2+][CO2]/[H+]2
d. [Ni2+][H+]2
e. [Ni2+]/[NiCO3]

5. Consider the following chemical reaction:
H2(g) + I2(g) 2HI(g)
At equilibrium, the concentrations of H2, I2, and HI were 0.15 M,
0.033 M, and 0.55 M, respectively. The value of Kc for this reaction
is
111
9.0 x 10-3
6.1
23
61

6. Consider the following reaction:

PCl5(g) PCl3(g) + Cl2(g)

Initially, 0.84 mol of PCl5(g) was placed in a 1.0 L flask. At
equilibrium, 0.72 mol of PCl5(g) was present. The value of Kc for
this reaction at this temperature is ___________.

a. 2.0 x 10-2
b. 0.62
c. 0.60
d. 0.12
e. 0.72

7. The value of Kc for the reaction below is 0.016. Under a set of
equilibrium conditions, [HI] = 0.10 M and [H2] = [I2]. Calculate the
concentration of I2 (M).
2HI(g) H2(g) + I2(g)

a. 1.3 M
b. 3.1 x 10-1
c. 0.31
d. 4.0 x 10-2
e. 1.3 x 10-2

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