2 chemistry questions?

1. Using the following balanced reaction
Cr2O3 + 2 Al = Al2O3 + 2 Cr
how many grams of Cr2O3 would be needed to produce 52 grams of Cr?
molar masses are Cr2O3 = 152, Al = 27, Al2O3 = 102, Cr = 52


2. Using the following balanced reaction
2 H2S + 3 O2 = 2 SO2 + 2 H2O
how many grams of H2O would be produced from 96 grams of O2?
Molar masses are H2S = 34, O2 = 32, SO2 = 64, H2O = 18

Answer:
I'll do the 1st one.
You are given grams and you want grams.
52 grams of Cr = 1 mole of Cr
The equation tells you than 1 mole of Cr2O3 will yield 2 moles of Cr; you need 1/2 mole of Cr2O3 to yield 1 mole of Cr (52g)

Cr2O3 MW is 152, to 1/2 mole of Cr2O3 is 76 g

You need 76 grams of Cr2O3 to produce 52 g of Cr.
1. 1/2 mole , 76g
2. 72g

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