Question

A compound contains atoms of three elements $A, B$ and $C$. If the oxidation number of $A$ is $+ 2, B$ is $+5$ and that of $C$ is $- 2$, the possible formula of the compound is

• A. $A_2(BC_3)_2$
• B. $A_3(BC_4)_2$
• C. $A_3(B_4C)_2$
• D. $ABC_2$

Answer 1

The Correct Option is B

To determine the possible formula of the compound containing elements A, B, and C with oxidation states +2, +5, and -2 respectively, we need to ensure that the sum of the oxidation numbers in the compound equals zero, which is a requirement for stable neutral chemical compounds.

1. The oxidation numbers of the elements are given as:
   • A: +2
   • B: +5
   • C: -2
2. Let's analyze each option to determine which one fits the requirement that the sum of the oxidation numbers equals zero:
3. A_2(BC_3)_2:
   • Total oxidation number from A_2: 2 \times (+2) = +4
   • One (BC_3)_2 unit contributes:
     • B: +5, and 2B gives +10
     • 3C: 3 \times (-2) = -6, and for two units: -12
4. Total: +4 + 10 - 12 = +2, which is not equal to zero, hence incorrect.
5. A_3(BC_4)_2:
   • Total oxidation number from A_3: 3 \times (+2) = +6
   • One (BC_4)_2 unit contributes:
     • B: +5, and 2B gives +10
     • 4C: 4 \times (-2) = -8, and for two units: -16
6. Total: +6 + 10 - 16 = 0, which satisfies the requirement for the sum to be zero, hence correct.
7. A_3(B_4C)_2:
   • Total oxidation number from A_3: 3 \times (+2) = +6
   • One (B_4C)_2 unit contributes:
     • B: 4 \times +5 = 20, and for 2 units: +40
     • C: -2, and for 2 units: -4
8. Total: +6 + 40 - 4 = +42, which is not equal to zero, hence incorrect.
9. ABC_2:
   • A: +2
   • B: +5
   • 2C: 2 \times (-2) = -4
10. Total: +2 + 5 - 4 = +3, which is not equal to zero, hence incorrect.

Therefore, the correct formula of the compound is A_3(BC_4)_2.