1. The reaction between hydrogen gas and oxygen gas to form water: 2H2 + O2 → 2H2O

2. The reaction between iron and sulfur to form iron sulfide: Fe + S → FeS

3. The reaction between magnesium and oxygen to form magnesium oxide: 2Mg + O2 → 2MgO

4. The reaction between nitrogen gas and hydrogen gas to form ammonia: N2 + 3H2 → 2NH3

5. The reaction between sodium and chlorine gas to form sodium chloride: 2Na + Cl2 → 2NaCl

6. The reaction between carbon and oxygen gas to form carbon dioxide: C + O2 → CO2

7. The reaction between lithium and oxygen to form lithium oxide: 4Li + O2 → 2Li2O

8. The reaction between aluminium and oxygen to form aluminium oxide: 4Al + 3O2 → 2Al2O3

9. The reaction between calcium and chlorine gas to form calcium chloride: Ca + Cl2 → CaCl2

10. The reaction between hydrogen gas and chlorine gas to form hydrogen chloride: H2 + Cl2 → 2HCl

In a combination reaction, two or more substances combine to form a single product. These reactions are also known as synthesis reactions.