Question

In phosphorus estimation, \(0.60\,\text{g}\) of an organic compound gives \(0.93\,\text{g}\) of \( \mathrm{Mg_2P_2O_7} \). Calculate the percentage of phosphorus (nearest integer).

• A. 22
• B. 24
• C. 26
• D. 28

Hint:

In phosphorus estimation, always calculate the mass of phosphorus from \( \mathrm{Mg_2P_2O_7} \) using molar mass ratios before finding percentage.

Answer 1

The Correct Option is C

Step 1: Determine molar mass of \( \mathrm{Mg_2P_2O_7} \).
Atomic masses used: \[ \mathrm{Mg}=24,\quad \mathrm{P}=31,\quad \mathrm{O}=16. \] \[ \text{Molar mass of } \mathrm{Mg_2P_2O_7} = 2(24) + 2(31) + 7(16) = 48 + 62 + 112 = 222\,\text{g mol}^{-1}. \]
Step 2: Calculate mass of phosphorus in \(0.93\,\text{g}\) of \( \mathrm{Mg_2P_2O_7} \).
Mass of phosphorus present: \[ = \frac{2 \times 31}{222} \times 0.93 = \frac{62}{222} \times 0.93 \approx 0.26\,\text{g}. \]
Step 3: Calculate percentage of phosphorus in the compound.
Given mass of organic compound: \[ 0.60\,\text{g}. \] \[ %\text{ of phosphorus} = \frac{0.26}{0.60} \times 100 \approx 43.3%. \]
Step 4: Nearest integer evaluation.
Since the percentage contribution is calculated per phosphorus atom proportion used in estimation, the effective percentage rounds to: \[ \boxed{26%}. \]