The formula of the ionic compound, gold(II) nitrite is (A) AuNO2(B) Au3N2(C) Au(NO3)2(D) Au(NO2)2
The Correct Answer and Explanation is :
The correct formula for gold(II) nitrite is (D) Au(NO2)2.
Explanation:
Gold(II) indicates that gold has a +2 oxidation state, which is critical for determining the compound’s formula. In ionic compounds, the oxidation states of the elements determine the ratio of ions in the formula. Nitrite, NO2−, has a −1 charge.
- Gold(II) means that gold has a +2 charge, so the gold ion is Au²⁺.
- Nitrite (NO2−) is an anion with a −1 charge.
For the compound to be electrically neutral, the charges of the gold cations and nitrite anions must balance. Since the gold ion has a +2 charge, two nitrite ions (each with a −1 charge) are required to balance the +2 charge. Therefore, the formula is Au(NO2)2.
Step-by-step reasoning:
- Determine the charge of gold(II): The Roman numeral (II) tells us that gold is in the +2 oxidation state, so the gold ion is Au²⁺.
- Determine the charge of nitrite: The nitrite ion (NO2−) has a charge of −1.
- Balance the charges: To balance the +2 charge of gold, we need two nitrite ions, each with a −1 charge. Thus, the formula is Au(NO2)2.
Why not the other options?
- (A) AuNO2: This would suggest that one Au²⁺ ion balances one NO2− ion, but the charges do not add up to zero. Gold(II) requires two nitrite ions to balance the charge.
- (B) Au3N2: This is a formula for gold(III) nitride, where gold would have a +3 oxidation state, not +2.
- (C) Au(NO3)2: This is the formula for gold(II) nitrate, not nitrite. Nitrate (NO3−) is different from nitrite (NO2−), which has a different formula.
Thus, the correct answer is (D) Au(NO2)2.