Question

The minimum molar mass of a compound containing $0.28$% of iron is:

• A. $100$ g/mol
• B. $200$ g/mol
• C. $10$ kg/mol
• D. $20$ kg/mol

Answer 1

The correct option is D $20$ kg/mol

Given, $0.28$ g of $Fe$ is present in $100$ g.

As we know, minimum 1 atom of Fe must be there in the compound, so for the minimum molar mass, we take the limiting case when the compound has exactly 1 Fe atom.
$\therefore 56$ g of $Fe$ is present in $\frac{100\times 56}{0.28}=20000$ g $=20$ kg
Thus, the minimum molar mass of a compound containing $0.28$% of iron is $20$ kg.