Zinc sulphate contains 22.65% Zn and 43.9% . If the law of constant proportions is true, then the ma — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

# Solution: Mass of Zinc in Zinc Sulphate Crystals **Step 1: Identify the composition** Zinc sulphate crystals contain: - Zn: 22.65% - $H_2O$: 43.9% - Therefore, $SO_4$: $100 - 22.65 - 43.9 = 33.45\%$ **Step 2: Apply the law of constant proportions** The law of constant proportions states that a pure compound always contains the same elements in the same mass ratio. Therefore, in any sample of zinc sulphate crystals, the mass percentage of Zn remains constant at 22.65%. **Step 3: Calculate mass of Zn in 40g crystals** $$\text{Mass of Zn} = \frac{22.65}{100} \times 40 \text{ g}$$ $$\text{Mass of Zn} = 0.2265 \times 40 = 9.06 \text{ g}$$ **Answer: 9.06 g (or approximately 9.1 g)** **Why this works:** Since the composition is constant by law of definite proportions, any 40g sample of this zinc sulphate hydrate will always contain exactly 22.65% zinc by mass, regardless of sample size.