In 420 ml of water, 40 g of sulfur oxide (VI) was dissolved. Calculate the mass fraction of sulfuric acid in the resulting solution.

Given:

V (H 2 O) = 420 ml;

m (substance) = 40 g.

W -?

Decision:

Mass fraction of a substance is calculated by the formula:

W = m (substance): m (solution) × 100%,

m (substance) = (m (solution) × W): 100%,

one.

m (solution) = m (substance) + m (water).

Let’s find the mass of water by the formula.

m = Vp

m (H2O) = 420 ml × 1 g / ml = 420 g.

m (solution) = 420 g + 40 g = 460 g.

2. Let’s compose the reaction equation for the dissolution of sulfur oxide in water.

H2O + SO3 = H2SO4

3.Let’s find the amount of sulfur oxide substance by the formula:

n = m: M.

M (SO3) = 80 g / mol.

n = 40 g: 80 g / mol = 0.5 mol.

According to the reaction equation, 1 mol of sulfur oxide accounts for 1 mol of acid. Substances are in quantitative ratios 1: 1. Their amount of substances will be the same.

n (SO3) = n (H2SO4) = 0.5 mol.

4. Let’s find the mass of sulfuric acid.

m = n × M.

M (H2SO4) = 98 g / mol.

m = 98 g / mol × 0.5 mol = 49 g.

5. Let’s find the mass fraction of acid in the solution.

W = (49g: 460g) × 100% = 10.65% = 10.7%.

Answer: 10.7%.