Indicate whether ΔS° is large and positive, large and negative, or nearly zero in each of the following reactions. (a) NH3(g) + HCl(g) → NH4Cl(s) large and positive large and negative nearly zero (b) N2H4(g) → N2(g) + 2 H2(g) large and positive large and negative nearly zero (c) H2(g) + I2(g) → 2 HI(g) large and positive large and negative nearly zero (d) HF(aq) + NO2− (aq) → F − (aq) + HNO2(aq) large and positive large and negative nearly zero
The logic for answering this question is explained first:
Entropy is a measure of dis-orderness of the system. Higher the entropy, higher the dis-orderness and vice-versa .
Gases are more dis-ordered than liquids and liquids are more dis-ordered than solids . Hence gases have more entropy than liquids and liquids have more entropy than solids. That is :
entropy of gases > entropy of liquids > entropy of solids
Hence in a reaction where more gas is produced, the entropy increases.
(a)
Answer:
entropy change is large and negative
Reason : 2 moles of gas is producing 1 mol of solid. Hence entropy decreases. Entropy before the reaction is much less than the entropy after reaction. Hence entropy change is large and negative.
(b)
Answer:
entropy change is large and positive
Reason : 1 mole of gas is producing 3 moles of gas. Hence entropy increases. Entropy before the reaction is much higher than the entropy after reaction. Hence entropy change is large and positive.
(c)
Answer:
entropy change is nearly zero
Reason : 2 moles of gas is producing 2 moles of gas.Entropy before the reaction is almost equal to the entropy after the reaction. Hence entropy change is nearly zero.
(d)
Answer:
entropy change is nearly zero
Reason : 2 moles of aqueous compounds are producing 2 moles of aqueous compounds .Entropy before the reaction is almost equal to the entropy after the reaction. Hence entropy change is nearly zero.
Indicate whether ΔS° is large and positive, large and negative, or nearly zero in each of...
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