Can someone please answer my question?

Question

Which of the reactions are exothermic?

2Mg(s)+O2(g)⟶2MgO(s)      Δ𝐻=−1203 kJ/mol

NH3(g)+HCl(g)⟶NH4Cl(s)    Δ𝐻=−176 kJ/mol

AgCl(s)⟶Ag+(aq)+Cl−(aq)     Δ𝐻=127 kJ/mol

2Fe2O3(s)+3C(s)⟶4Fe(s)+3CO2(g)   Δ𝐻=468 kJ/mol

C(graphite)+O2(g)⟶CO2(g)   Δ𝐻=−393.5 kJ/mol



CH4(g)+2O2(g)⟶CO2(g)+2H2O(l) Δ𝐻=−891 kJ/mol

Answer 1

If the sign for ∆H is negative, then the reaction, as written, is exothermic.