i. i.stoichiometric calculations stoichiometry. history of stoichiometry b comes from the greek:...

I. Stoichiometric

Calculations

I. Stoichiometric

Calculations

StoichiometryStoichiometry

History of StoichiometryHistory of StoichiometryHistory of StoichiometryHistory of Stoichiometry

Comes from the Greek:

Stoicheion

- to measure the elements

History of StoichiometryHistory of StoichiometryHistory of StoichiometryHistory of Stoichiometry

Joseph Black and Daniel Rutherford

studied the reaction

CaCO3 CaO + CO2

They were looking at how the mass was changing in the reaction. They realized there the relation in the changing mass was actually in moles of substance.

Proportional Proportional RelationshipsRelationshipsProportional Proportional RelationshipsRelationships

StoichiometryStoichiometry• mass relationships between

substances in a chemical reaction• based on the mole ratio

Mole RatioMole Ratio• indicated by coefficients in a

balanced equation

2 Mg + O2 Mg + O22 2 MgO 2 MgO

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas?

9 mol O2 2 mol KClO3

3 mol O2

= 6 mol KClO3

2KClO3 2KCl + 3O2 ? mol 9 mol

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

How many moles of KCl are produced when 3.6 mol of KCLO3 are decomposed?

3.6 mol KClO3

2 mol KCl2 mol KClO3

= 7.2 mol KCl

2KClO3 2KCl + 3O2 ? mol3.6 mol

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

Do Mole to Mole WS

Stoichiometry StepsStoichiometry Steps Stoichiometry StepsStoichiometry Steps

1. Write a balanced equation.2. Identify known & unknown.3. Line up conversion factors.

• Mole ratio - moles moles• Molar mass - moles grams• Molarity - moles liters soln• Molar volume - moles liters gas

Core step in all stoichiometry problems!!

• Mole ratio - moles moles

4. Check answer.

1 mol of a gas=22.4 Lat STP

Molar Volume at STPMolar Volume at STP Molar Volume at STPMolar Volume at STP

Standard Temperature & Pressure0°C and 1 atm

““Stoich – nid”Stoich – nid”““Stoich – nid”Stoich – nid”

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

How many grams of silver will be formed when 12.0 g copper react with excess

aqueous silver nitrate?

12.0g Cu

1 molCu

63.55g Cu

= 40.7 g Ag

Cu + 2AgNO3 2Ag + Cu(NO3)2

2 molAg

1 molCu

107.87g Ag

1 molAg

12.0 g ? g

63.55g Cu

1 molCu

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

How many grams of Copper atoms are required to react completely with 1.5 x 1023 formula units of AgNO3?

1.5 x 1023

Form units AgNO3

1molAgNO3

6.022 x 1023

Form units AgNO3

= 7.9 g Cu

Cu + 2AgNO3 2Ag + Cu(NO3)2

1 mol Cu

2 molAgNO3

? g 1.5 x 1023

form units

How many grams of KClO3 are req’d to

produce 9.00 L of O2 at STP?

9.00 LO2

1 molO2

22.4 L O2

= 32.8 g KClO3

2 molKClO3

3 molO2

122.55g KClO3

1 molKClO3

? g 9.00 L

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

2KClO3 2KCl + 3O2

Stoichiometry ProblemsStoichiometry ProblemsStoichiometry ProblemsStoichiometry Problems

Do Stoich WS 1