Question

Sphalerite shows limited isomorphism. Consider a colorless sphalerite having 33% S and 67% Zn. Then, in a black-coloured sphalerite, with a 15% Fe substitution, the ratio of atomic proportions of Zn to that of Fe is ...........

Hint:

To find the atomic ratio of two elements, calculate the number of moles of each element using the atomic weights and then divide the moles of one element by the moles of the other element.

Answer 1

Correct Answer: 1.1

Step 1: Set the weight percents.
With 15 percent of the metal site as Fe, the rest, 85 percent, is Zn. We compare their atomic amounts.

Step 2: Recall atomic weights.
Zinc weighs about 65.37 and iron about 55.85. We turn weight percent into moles by dividing by these.

Step 3: Find the moles.
Moles of Zn are $85 / 65.37 \approx 1.30$. Moles of Fe are $15 / 55.85 \approx 0.27$.

Step 4: Take the ratio.
The atomic ratio is \[ \frac{1.30}{0.27} \approx 1.1. \]

Step 5: State the answer.
So Zn to Fe by atoms is about 1.1.
\[ \boxed{1.1} \]