Explanation:
The reaction expression is given as;
2H₂ + O₂
→ 2H₂O
From the balance reaction expression:
2 mole of hydrogen gas combines with 1 mole of oxygen gas on the reactant side;
This produces 2 mole of water on the product side of the expression.
The product is in liquid form.
This reaction is a synthesis reaction because a single product is formed from two reactants.