Answer to Question #78483 in General Chemistry for Chloe Lozano

Question

In which of the following equations is ΔS negative? _______

A. 4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g)
B. Zn (s) + HCl (aq) → ZnCl2 (aq) + H2 (g)
C. NaCl (s) + H2SO4 (l) → NaHSO4 (s) + HCl (g)
D. 2NH4NO3 (s) + Ba(OH)2(H2O)8 (s) → Ba(NO3)2 (aq) + 2NH4OH (aq) + 8H2O (l)
E. NaCl (aq) + H2O (l) + CO2 (g) → NaHCO3 (aq) + HCl (l)

Answer 1

E. NaCl (aq) + H2O (l) + CO2 (g) → NaHCO3 (aq) + HCl (l)

In general, any reaction that involves a net increase in the number of moles of gas (more moles of gas on the product side than on the reactant side) will have a positive ΔS. This reaction has 1 mole of gas on the reactant side, and no gas on the product side, so ΔS < 0.