Question

question 80 (1 point)
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the correct formulas for iron(iii)sulfide and cobalt (ii)phosphide are:

1. pbs and co₂k₂
2. fe₃so₄ and co₃po₄
3. pb₃s₂ and co₂p₃
4. fe₂s₃ and co₃p₂

Explanation:

Step1: Analyze Iron(III) Sulfide

Iron(III) has a charge of \(+3\) (\(Fe^{3+}\)), sulfide ion is \(S^{2-}\). To balance charges, use the criss - cross method: the charge of Fe becomes the subscript of S and vice - versa. So, for \(Fe^{3+}\) and \(S^{2-}\), the formula is \(Fe_2S_3\) (since \(3\times2 = 2\times3\) for charge balance).

Step2: Analyze Cobalt(II) Phosphide

Cobalt(II) has a charge of \(+2\) (\(Co^{2+}\)), phosphide ion is \(P^{3-}\). Using the criss - cross method, the charge of Co (\(2\)) becomes the subscript of P and the charge of P (\(3\)) becomes the subscript of Co. So the formula is \(Co_3P_2\) (since \(2\times3=3\times2\) for charge balance).

Now let's check the options:

• Option 1: Contains \(Pb\) (lead) instead of \(Fe\) (iron) and incorrect ions, so wrong.
• Option 2: Incorrect ions (has sulfate and phosphate instead of sulfide and phosphide), so wrong.
• Option 3: Contains \(Pb\) (lead) instead of \(Fe\) (iron), so wrong.
• Option 4: Has \(Fe_2S_3\) (correct for iron(III) sulfide) and \(Co_3P_2\) (correct for cobalt(II) phosphide).

Answer:

1. \(Fe_2S_3\) and \(Co_3P_2\)