The reaction between elemental phosphorus p4 (s) and o2 (g) to make p4o10 (s) :

The reaction between elemental phosphorus p4 (s) and o2 (g) is a synthesis type of reaction where two elements combine together to form a compound. Balancing the equation, we get P4 (s) + 5 O2 (g) = P4O10 (s). Here the number of oxygen molecules are balanced on either side by adding 5 molecules of O2 on the product side.