Question

How many grams of product form when 17.8 g of O2 reacts completely? (Assume you have enough Cr) Chromium solid reacts with oxygen gas to form chromium (III) oxide How many moles of Cr(s) is needed for 17.8 g of oxygen gas to react completely

Answer 1

4 Cr + 3 O2 —> 2 Cr2O3

1)

mass of O2 = 17.8 g

molar mass of O2 = 32 g/mol

mol of O2 = (mass)/(molar mass)

= 17.8/32

= 0.5563 mol

According to balanced equation

mol of Cr2O3 formed = (2/3)* moles of O2

= (2/3)*0.5563

= 0.3708 mol

mass of Cr2O3 = number of mol * molar mass

= 0.3708*152

= 56.4 g

Answer: 56.4 g

2)

According to balanced equation

mol of Cr needed = (4/3)* moles of O2

= (4/3)*0.5563

= 0.742 mol

Answer: 0.742 mol