Chapter 12

Stoichiometry

Reaction – Stoichiometry Problems

Identify the information given

Identify the unknown, the information you are expected to find.

Given Unknown

Given amount in moles

Mole to Mole Ratio

Unknown amount in moles

Given amount in grams (A)Given amount in moles (A)

Mole B / Mole A

Unknown amount in moles (B)

Given amount in grams (A) Molar Mass AGiven amount in moles (A)

Mole B / Mole A

Unknown amount in moles (B)

Grams A

Moles A

Moles B

Grams A

Moles A

Moles B

Grams B

Grams A Molar Mass A

Moles A Mole B/ Mole A

Moles B Molar Mass B Grams B

Problem

In photosynthesis, plants use energy from the sun to produce glucose, C6H12O6, and oxygen from the reaction of carbon dioxide and water.

What mass, in grams, of glucose is produced when 3.00 moles of water react with carbon dioxide?

Answer 3.00 mole H2O

x 1 mole C6H12O6 =

6 mole H2O

x 180.16 g C6H12O6 = 90.1 g C6H12O6

1 mole C6H12O6

Problem NH3(g) + O2(g) NO (g) + H2O (g)

Balance this equation!!

If the reaction is run with 824 g of NH3, and excess oxygen, how many moles of NO and H2O are formed?

Answer 4NH3(g) + 5O2(g) 4NO (g) + 6H2O (g)

824 g x 1 mole NH3 x 4 mole NO

17.031 g NH3 4 mole NH3

= 48.4 mole NO

Answer

824 g x 1 mole NH3 x 6 mole H2O

17.031 g NH3 4 mole NH3

= 72.6 mole H2O