Answer:
I dont lnow much about chemistry, but I believe it's either d or a. sorry if its wrong!
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.
The catalyst (4) decreases the activation energy required for a reaction, by holding reactants in place