21. Determine the amount of heat given off or absorbed by each of processes. BELOW ARE THE ANSWERS BUT I NEED EXPLAINING. In problem “a” where did -201.2kj/mol gas and -237.6 jk/mol liquid come from? PLEASE HELP

a) evaporation of 0.80 g of CH3OH Reaction: 0.025 CH3OH(l) Æ 0.025 CH3OH(g)

q = (0.025 mols gas)(-201.2 kJ/mol gas) – (0.025 mols liquid )(-237.6 kJ/mol liquid) = 0.91 kJ absorbed

b) decomposition of 3.2 g of CaCO3(s) to CaO(s) and CO2(g) Reaction: 0.032 CaCO3(s) Æ 0.032CaO(s) + 0.032 CO2 (g)

q = (0.032 mol CaO)(-635.1) +(0.032 mol CO2)(-393.51 kJ/mol) – (0.032 mol CaO)(1206.9 kJ/mol) = 5.7 kJ absorbed

c) reaction of 4.0 g of H2(g) with excess N2(g) to produce NH3(g) 2.0 H2(g) + 0.67 N2 (g) Æ 1.3 NH3(g)

q = (1.3 mol NH3)(-46.11 kJ/mol) = – 61.48 kJ 61.48 kJ are released.

d) reaction of 12 g of NH3(g) with excess HCl(g) to produce NH4Cl(s) 0.71 NH3(g) + 0.71 HCl (g) Æ 0.71 NH4Cl(s) q = (0.71 mol){ -314.4 -(-46.11) – (-92.30)} kJ/mol= -1.2 x 102 kJ 120 kJ of heat are released.