Question

What is the mass of water formed in the following reaction?

Acid + Base $\to$ Salt + Water
35 g 40 g 57 g ? [2 Marks]

Answer 1

According to the law of conservation of mass, the total mass of the reactants is equal to the total mass of the products.

The total mass of the reactants = Mass of acid + mass of base
$⟹$ 35 + 40 = 75 g
[1 Mark]

Let the mass of the water formed be X grams.
The total mass of the products = Mass of salt + mass of water = (57 + X) g
On equating the mass of reactants with that of products, we get,
57 + X = 75
$⟹$ X = 18 g

Hence, the mass of water formed in the reaction is 18 g.
[1 Mark]