Question 29 of 43intermediate🔧 ApplyMCQ1 mark

You want to design a new ionic compound, where the total positive charge is 6+ and the total negative charge is 6−. Which of the following combinations gives the correct number of ions?

Exercise: Revise, Reflect, Refine | Q: 3 | (Page 20)
For More Understanding

Explanation

Option (iii) is correct because in an ionic compound, the total positive and negative charges must balance each other to make the overall structure neutral. For the combination of 2 Fe³⁺ and 3 O²⁻, the total positive charge is 2 × (+3) = 6+, and the total negative charge is 3 × (−2) = 6−. This perfectly matches the required total positive charge of 6+ and total negative charge of 6−. The other options do not balance to 6+ and 6−.

Solution Steps

  1. Step 1: Evaluate option (i) - 2 Al³⁺ and 3 Cl⁻. Total positive charge = 2×32 \times 3+ = 6+. Total negative charge = 3×13 \times 1− = 3−. (Incorrect, as negative charge is not 6−)

  2. Step 2: Evaluate option (ii) - 3 Mg²⁺ and 1 PO₄³⁻. Total positive charge = 3×23 \times 2+ = 6+. Total negative charge = 1×31 \times 3− = 3−. (Incorrect, as negative charge is not 6−)

  3. Step 3: Evaluate option (iii) - 2 Fe³⁺ and 3 O²⁻. Total positive charge = 2×32 \times 3+ = 6+. Total negative charge = 3×23 \times 2− = 6−. (Correct, as both charges match the required 6+ and 6−)

  4. Step 4: Evaluate option (iv) - 3 Ca²⁺ and 2 SO₄²⁻. Total positive charge = 3×23 \times 2+ = 6+. Total negative charge = 2×22 \times 2− = 4−. (Incorrect, as negative charge is not 6−)

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