Which of the reactions are spontaneous (favorable)?
$NH_3(g) + HCl(g) \longrightarrow NH_4Cl(s)$ $\Delta G = -91.1$ kJ/mol
$AgCl(s) \longrightarrow Ag^+(aq) + Cl^-(aq)$ $\Delta G = 55.6$ kJ/mol
$2Mg(s) + O_2(g) \longrightarrow 2MgO(s)$ $\Delta G = -1137$ kJ/mol
$C(s) + H_2O(l) \longrightarrow CO(g) + H_2(g)$ $\Delta G = 90.8$ kJ/mol
$2H_2O(g) \longrightarrow 2H_2(g) + O_2(g)$ $\Delta G = 457$ kJ/mol
$CH_4(g) + 2O_2(g) \longrightarrow CO_2(g) + 2H_2O(l)$ $\Delta G = -820$ kJ/mol