For the process Cl_2(g) rightarrow 2Cl(g), A) Delta H is + and Delta S is + for

Question

For the process Cl_2(g) rightarrow 2Cl(g), A) Delta H is + and Delta S is + for the reaction B) Delta H is + and Delta S = 0 for the reaction. C) Delta H is - and Delta S is - for the reaction D) Delta H is - and Delta S is + for reaction E) Delta H is + and Delta S is - for the reaction. What is the thermodynamic quantity that provide the criterion for the spontaneity of a chemical reaction? A) T Delta S B) Delta U C) Delta S D) Delta S D) Delta G E) Delta H What is Delta G degree at 298 K for the following reaction? I_2(g) + Br_2(g) rightarrow 2IBr(g); Delta H degree = -11.6 kJ; Delta S degree = 12 J/K at 298 K A) -8.02 kJ B)15.2 kJ C) -15.2 kJ D) 3.59 times 10^3 kJ E) -3.59 times 10^3 kJ

Explanation / Answer

1. H is positive (+ve) as the energy is absorbed during bond breakage.

S is positive (+ve) as entropy increased during when the molecule is broken to form atoms.

So, the answer is

A) H is + and S is + for the reaction.

2. If the Gibbs free energy (G) is negative, then the reaction is spontaneous and If the Gibbs free energy (G) is positive, then the reaction is non-spontaneous. So, the Gibbs free energy (G) provides the spontaneity of a chemical reaction.

So, the answer is

D) G

3. Gibb’s equation is

G° = H° – TS°

where G° = Gibb's free energy

H° = Change in enthalpy = -11.6 kJ

T = Temperature = 298 K

S° = Change in entropy = 12 J/K = 0.012 kJ/K

G° = H° – TS° = -11.6 kJ - (298 K) (0.012 kJ/K) = -11.6 kJ - 3.58 kJ = -15.18 kJ

G° =  -15.2 kJ

So, the answer is

C) -15.2 kJ

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