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 what we know** - Zinc sulphate crystals contain 22.65% Zn by mass - We need to find the mass of Zn in 40 g of crystals - The law of constant proportions states that compounds always contain the same proportion of elements **Step 2: Apply the law of constant proportions** If zinc sulphate crystals consistently contain 22.65% Zn, then in any sample: $$\text{Mass of Zn} = \text{Mass of crystals} \times \frac{\% \text{ of Zn}}{100}$$ **Step 3: Calculate** $$\text{Mass of Zn} = 40 \text{ g} \times \frac{22.65}{100}$$ $$\text{Mass of Zn} = 40 \times 0.2265 = 9.06 \text{ g}$$ **Step 4: Conclusion** The law of constant proportions guarantees that regardless of the source or method of preparation, zinc sulphate crystals always contain exactly 22.65% zinc. Therefore, **9.06 g of Zn** is required to obtain 40 g of crystals. This demonstrates that the elemental composition remains invariant—a fundamental principle of chemistry.