Predict the sign of the entropy change of the system for each of the following reactions. (a) n2(g)+3h2(g)→2nh3(g) (b) caco3(s)→cao(s)+co2(g) (c) 3c2h2(g)→c6h6(g) (d) al2o3(s)+3h2(g)→2al(s)+3h2o(g) socratic.org

a. Negative

b. Positive

c. Negative

d. zero

Explanation:

Entropy is measure of disorder. Positive entropy implies that a system is becoming more disordered. The opposite is true.

(a) N2(g)+3H2(g) → 2NH3(g) Negative because the system is becoming less disordered since the number of gaseous moles is decreasing

(b) CaCO3(s)→CaO(s)+CO2(g)  Positive because a solid produces a gas which is more disorder therefore there is an increase in entropy

(c) 3C2H2(g)→C6H6(g) Negative because the number of moles of a gas decrease meaninng there is less disorder

(d) Al2O3(s)+3H2(g) → 2Al(s)+3H2O(g) zero because the gaseous moles do not change

HNO₃.

Explanation:

It is known that acids decrease the pH of the solution, while bases increase  the pH of the solution.

So, HF and HNO₃ decrease the pH of the solution as they produce H⁺ in the solution.

While, KOH and NH₃ increase the pH of the solution as they produce OH⁻ in the solution.

HNO₃ will decrease the pH of the solution greater than HF.

Because HNO₃ is strong acid that decomposes completely to produce H⁺ more than the same concentration of HF that is a weak acid which does not decomposed completely to produce H⁺.