Stoichiometry

Math behind Chemistry

Review

• Student knows how to calculate molar mass of a compound.• Find the molar

mass of dinitrogen tetraoxide.

• Student knows how to convert from grams to moles and moles to grams using molar mass.• Example: How

many moles are in 12.56 grams of NaCl?

Mole to Mole

• Mole Ratios • A ratio between compounds that comes

from the coefficients of balanced equation of a chemical equation.

• Written 3 ways:• Fraction 3/2• Words 3 to 2• Colon 3:2

Mole Ratios

• Must come from balanced chemical equation, whether equation is given to you to balance or word equations.• Example: When Calcium iodide

combines with Sodium oxide, calcium oxide and sodium iodide are formed. Write the chemical formulas and balance it.

•1CaI2 + 1Na2O 1CaO + 2NaI

Mole Ratios cont

•1CaI2 + 1Na2O 1CaO + 2NaI

• Identify all the ratios that can be made possible.

• 1 to 1 • 1 to 1 • 1:2• 1:1• ½ • 1 to 2

Mole to Mole Conversion

• Once you have balanced equation, you convert from moles of one compound to moles of a different compound.

• Let’s use the previous example to solve a problem.• 1CaI2 + 1Na2O 1CaO + 2NaI

• How many moles would form of CaO if an experiment started with 6.74 moles of Na2O?

Example 1

•1CaI2 + 1Na2O 1CaO + 2NaI• How many moles would

form of CaO if an experiment started with 6.74 moles of Na2O?

6.74 moles Na2O 6.74 moles CaO

Mole ratio from balanced equation

Example 2

•1CaI2 + 1Na2O 1CaO + 2NaI•How many moles of CaI2 are needed if 5.32 moles of NaI are formed?

Example 3

• Write the balanced equation:

•Aluminum bromide and Chlorine react to form aluminum chloride and bromine. 1. How many moles of bromine are formed

if an experiment starts with 4.61 moles aluminum bromide?

2. How many moles of chlorine are needed to form 7.88 moles of bromine?

Recap

•Students know how to:A. Calculate molar mass

B.Convert mass to moles

C.Convert moles of known compound to moles of unknown compound using mole ratios

Learning Check

Potassium metal and chlorine gas combine to potassium chloride.

1. Calculate the molar mass of chlorine

2. Convert 5.87 grams of chlorine to moles of chlorine.

3. Using the moles of chlorine from step 2, how many moles of potassium chloride will form?