A sample of has Ca = 40%, C = 12% and O = 48%. If the law of constant proportions is true, then the — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

# Solution: Law of Constant Proportions **Understanding the Law of Constant Proportions:** The law states that a pure compound always contains the same elements in the same fixed mass ratio, regardless of its source. **Given Information:** - Sample composition: Ca = 40%, C = 12%, O = 48% - We need to find mass of Ca in 5 g of $CaCO_3$ from another source **Step-by-step Solution:** 1) **Verify the given sample is pure $CaCO_3$:** - Molar mass of $CaCO_3$ = 40 + 12 + 48 = 100 g/mol - Ca: $\frac{40}{100} \times 100\% = 40\%$ ✓ - The percentages confirm a pure sample 2) **Apply Law of Constant Proportions:** Since $CaCO_3$ from any source has the same composition, it will always contain 40% Ca by mass. 3) **Calculate mass of Ca in 5 g:** $$\text{Mass of Ca} = \frac{40}{100} \times 5 \text{ g} = 2 \text{ g}$$ **Answer: The mass of Ca in 5 g of $CaCO_3$ from another source is 2 g** This is true because the law guarantees constant composition in all pure samples of the same compound.