Question

how many mole of Cr are in 85g of Cr2S3? (Cr=52,S=32)

Answer 1

The molar mass of the compound is 104+96=200g, so the no of moles of compound is 85/200. In one mole of compound, there are 2 moles of Cr. So, in 85/200 moles of compound there are 85/100 moles of Cr which is 0.85 moles.

Answer 2

Molar mass of Cr2S3 = 52+52+(32×3).
= 200g /mol
moles of Cr2S3 in 85 g of it = 85/200
= 0.425 moles
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1 mol of Cr2S3 contains = 2 moles of Cr
=> 0.425 moles of Cr2S3 contains →
2×0.425 = 0.85 moles of Cr.
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hope it helps!