Question

The molecular formula of ammonium sulphate is

• A. ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$
• B. ${\mathrm{NH}}_2{\mathrm{SO}}_4$
• C. ${\mathrm{NH}}_4{\mathrm{SO}}_4$
• D. None of these

Answer 1

The correct option is A

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$

The explanation for the correct option:

A. ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$

Molecular formula:

• “A molecular formula determines the number of atoms of each element in a compound.”
• The molecular formula of Ammonium sulfate is ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$.
• The given molecular formula is ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$ as ammonium ion $\left({\mathrm{NH}}_4^{+}\right)$ has +1 charge and sulphate ion $\left({\mathrm{SO}}_4^{2-}\right)$has -2 charge. for the neutrality of charges in the molecule, there will be 2 in the subscript of ${\mathrm{NH}}_4^{+}$ ion.
• Hence, the correct molecular formula is ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$.

The explanation for incorrect options:

B. ${\mathrm{NH}}_2{\mathrm{SO}}_4$

• The formula of ammonium ion is incorrect. the formula of ammonium ion is ${\mathrm{NH}}_4^{+}$ not ${\mathrm{NH}}_2^{+}$.

C. ${\mathrm{NH}}_4{\mathrm{SO}}_4$

• The ammonium ion bears +1 charge. However, in the given formula, the charge on the ammonium ion is +2 which is cancelled out with the charge on the sulphate ion $\left({\mathrm{SO}}_4^{2-}\right)$ for neutrality.

Hence, the correct option is A i.e. ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$.