Define exothermic reaction.

Choose the correct type of chemical reactions (Combination reaction/ decomposition reaction/ displacement reaction).

$2\mathrm{CO} + {\mathrm{O}}_2 \to 2{\mathrm{CO}}_2$

Choose the correct type of chemical reactions (Combination reaction/ decomposition reaction/ displacement reaction).

$\mathrm{C} + {\mathrm{O}}_2 \to {\mathrm{CO}}_2$

Choose the correct type of chemical reactions (Combination reaction/ decomposition reaction/ displacement reaction).

$2{\mathrm{Pb}}_3{\mathrm{O}}_4 \stackrel{∆}{\to } 6\mathrm{PbO} + {\mathrm{O}}_2$

Choose the correct type of chemical reactions (Combination reaction/ decomposition reaction/ displacement reaction).

${\mathrm{PCl}}_5\underset{\mathrm{Cool}}{ \stackrel{∆}{\rightleftharpoons }} {\mathrm{PCl}}_3 + {\mathrm{Cl}}_2$

Choose the correct type of chemical reactions (Combination reaction/ decomposition reaction/ displacement reaction).

$\mathrm{Zn} + {\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{ZnSO}}_4 +{\mathrm{H}}_2$