Please explain how to solve this

Question

Chromium metal can be produced from the high temperature reaction Cr2O3 [chromium ||| oxide ] with silicon or aluminum by each of the following reactions

2 Cr2O3 + 3Si -> 4 Cr + SiO2


Calculate the number of grams of silicon required to prepare 115g of chromium metal by the second reaction

Answer 1

Use stoichiometric coefficients to find molar rstion between chromium and silicon.  3 moles of silicon make 4 moles of chromium.

 

A) convert 115g of chromium into moles.

 

# moles=(115/1)*(1 mole Cr/52.01) or 2.21 moles Cr.

 

B) find # grams Si needed to make Cr.

 

# moles Si=2.21 moles Cr*(3 moles Si/4 moles Cr) or 0.553 moles Si.

 

# grams Si=0.553 moles Si*(28.086 g Si/1 mole Si) or 15.53 g Si