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 chemical compound always contains the same elements in the same fixed mass ratio, regardless of its source. **Step 1: Identify the given composition** - Ca = 40% - C = 12% - O = 48% These percentages represent the fixed mass ratio in $CaCO_3$. **Step 2: Apply the law to a new sample** Since the law of constant proportions holds true, any sample of $CaCO_3$ from any source must have the same percentage composition. Therefore, in 5 g of $CaCO_3$ from another source: $$\text{Mass of Ca} = 40\% \times 5 \text{ g}$$ **Step 3: Calculate** $$\text{Mass of Ca} = \frac{40}{100} \times 5 = 2 \text{ g}$$ **Answer: 2 g** The law of constant proportions guarantees that the mass fraction of each element remains constant across all samples of the same pure compound, making the answer independent of the source of $CaCO_3$.