Question

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the correct formulas for iron(iii)sulfide and cobalt (ii)phosphide are:

1. pbs and co₂k₂
2. fes and co₂p₃
3. pb₃s₂ and co₂k₃
4. fe₂s₃ and co₃p₂

Explanation:

Step1: Determine the symbol and charge of iron(III)

Iron(III) is \(Fe^{3+}\), sulfide is \(S^{2 -}\). Using the criss - cross method (the magnitude of the charge of one ion becomes the subscript of the other ion), for \(Fe^{3+}\) and \(S^{2 -}\), the formula is \(Fe_{2}S_{3}\) (\(3\times2 = 2\times3\)).

Step2: Determine the symbol and charge of cobalt(II)

Cobalt(II) is \(Co^{2+}\), phosphide is \(P^{3 -}\). Using the criss - cross method, for \(Co^{2+}\) and \(P^{3 -}\), the formula is \(Co_{3}P_{2}\) (\(2\times3=3\times2\)).

Answer:

1. \(Fe_{2}S_{3}\) and \(Co_{3}P_{2}\)