Question

Beryllium gives a compound X with the following percentage composition: Be = 6.1%, N = 37.8%, Cl = 48%, H = 8.1%. The molecular weight of X is 148 g/mol and that of Be is 9 g/mol. The molecular formula of the compound is:

• A. BeN4Cl2H12
• B. BeN2ClH6
• C. BeN4Cl2H6
• D. BeN4ClH8

Hint:

In molecular formula calculation, the percentage composition gives the proportion of each element, and from this, we calculate the number of moles of each element in the compound.

Answer 1

The Correct Option is A

Given that the molecular weight of X is 148 g/mol and the molecular weight of Be is 9 g/mol, we can calculate the molar masses of N, Cl, and H from the given percentages. The total moles of each element in the compound can be found using the following relationships:

- The moles of Be = \( \frac{6.1}{9} \)
- The moles of N = \( \frac{37.8}{14} \)
- The moles of Cl = \( \frac{48}{35.5} \)
- The moles of H = \( \frac{8.1}{1} \)

By calculating the number of atoms of each element, we can determine that the compound’s formula is BeN4Cl2H12. This formula is consistent with the molar masses and the percentages of each element in the compound.

Therefore, the correct molecular formula of the compound is (a) BeN4Cl2H12.