Question

The ratio of mass of 'x' atoms of an element to mass of carbon atoms is 9:1. Find the mass of 1 mol of x if molar mass of carbon is 12 g/mol.

• A. \(54 \text{g}\)
• B. \(108 \text{g}\)
• C. \(180 \text{g}\)
• D. \(216 \text{g}\)

Hint:

Multiply the ratio by the molar mass of carbon taken as the reference for one atom.

Answer 1

The Correct Option is B

Step 1: Set up a proportion
Both elements contain the same number of atoms in one mole, so the molar masses stand in the same ratio as the single-atom masses.
That gives $\frac{M_x}{12} = \frac{9}{1}$.

Step 2: Solve
Cross-multiplying, $M_x = 12 \times 9 = 108$ g per mole.
The mass of one mole of $x$ is therefore $108$ g.

Step 3: Why the others fail
Options $54 g$, $180 g$ and $216 g$ correspond to ratios $4.5$, $15$ and $18$ with carbon, none of which is the given $9:1$.

Final Answer:
The mass of 1 mol of x is 108 g. \[ \boxed{\text{(B)}\ 108\ \text{g}} \]