Question

# 1) Given the following thermochemical reaction and thermodynamic data, find Gibbs Free Energy, ΔG, and determine...

1) Given the following thermochemical reaction and thermodynamic data, find Gibbs Free Energy, ΔG, and determine if the reaction is spontaneous or non-spontaneous at 25 °C?

N2(g) + 3H2(g) → 2NH3(g) ΔH = -91.8 kJ

ΔS[N2] = 191 J / mol · K, ΔS[H2] = 131 J / mol · K, and ΔS[NH3] = 193 J / mol · K

a.98.3 kJ; Non-Spontaneous

b.-98.3 kJ; Spontaneous

c.32.7 kJ; Non-Spontaneous

d.ΔG = -32.7 kJ; Spontaneous

2) What is the oxidation number for selenium in the Selenate Ion, SeO4-2?

 a. +6 b. +3 c. -3 d. -6

3) Given the following electrochemical reaction, identify the reducing agent.

2Al(s) + 3F2(g) → 2AlF3(s)

a.

Fluorine (F2)

b.

Aluminum (Al)

c.

Aluminum Fluoride (AlF3)

4) Calculate the cell potential, E°cell, for the following electrochemical reaction.

Cu(s) + I2(g) → Cu+2(aq) + 2I-1(aq) E = ?

a.-0.87 V

b.-0.19 V

c.0.19 V

d.0.87 V

Now,

∆S = (∆S of product ) - (∆S of reactant)

= (2× 193) - (191+ 3×131)

= - 198 J/ mol K

= - 0.198 kJ / mol K

Now,,

T = 25+273 = 298 K

So , putting the values in above equation,,

So, option (d) is the correct answer.

-----------

SeO42-

Se + (-2)×4 = -2

Se = +6

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Aluminium is the reducing agent, because it is oxidized in the reaction and reduce the fluorine .

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