Question

The amount of water that can be ionised by the amount of heat liberated when 49 g of H2SO4 and 20 g NaOH are mixed and reacted in aqueous solution is __ gms: 1)9 2)36 3)27 4)18

Answer 1

we have to find the amount of water that can be ionised by the amount of heat liberated when 49g of H₂SO₄ and 20g NaOH are mixed and reacted in aqueous solution.

solution : as we know, H₂SO₄ is an acid and NaOH is a base. reaction of acid and base gives salt and water as product.

so, H₂SO₄ + 2NaOH ⇒Na₂SO₄ + 2H₂O

here it is clear that one mole of sulphuric acid reacts with two moles of sodium hydroxide and form one mole of sodium sulphate and two moles of water.

given mass of H₂SO₄ = 49 g

molecular mass of H₂SO₄ = 98 g/mol

so no of moles = 49/98 = 0.5

similarly, given mass of NaOH = 20g

molecular mass of NaOH = 40 g/mol

so no of moles = 20/40 = 0.5

from above, 0.5 mole of H₂SO₄ reacts with 1 mole of NaOH

so NaOH is limiting reagent.

now 2 moles of NaOH produce 2 mole of water

so, 0.5 mole of NaOH produce 0.5 mole of water..

so amount of water = mole × molecular mass of water

= 0.5 × 18 = 9

Therefore amount of water is 9g.