Reacting Masses

Starter:

Calculate the formula mass of the following compounds:

• H2O

• CO2

• HNO3

• Ca(OH)2

Dropdown

Calculate the formula masses:

H₂O ​​

Select answer

CO₂ ​

Select answer

HNO₃ ​

Select answer

Ca(OH)₂ ​

Select answer

Drag and Drop

A: ​

Placeholder

B: ​

Placeholder

C:​ Moles

Drag these tiles and drop them in the correct blank above

Mass

Mr

Ar

6.02x1023

6.02x10.23

Practice

•5 moles of H₂O = _____g

•0.25 moles of CO2 = _____g

•1.5 moles of HNO₃ = _____g

•0.01 moles of Ca(OH)₂ = _____g

Using the equation calculate the masses of the following

Reacting Masses: Ratios

What does this equation tell us about the ratios?

If I had 5 moles of Carbon how many moles copper and carbon dioxide

would I make?

2CuO + C 2Cu + CO2

Reacting Masses: Table

•So we can use the ratio of a balanced equation to work out the moles
of a substance
•Once we have moles we can calculate everything else

Substance X

Substance Y

Ratio

Mass

Mr

Moles

Put in the stuff we know

first

Example

How much copper can be made using 10g of carbon?

2CuO + C 2Cu + CO2

Carbon (C)

Copper (Cu)

Ratio

1

2

Mass (g)

10

106.45

Mr

12

63.5

Moles

0.833

1.67

Reacting Masses: Table

•Add in the information you know in the correct column

Calculate the moles of one of the chemicals

Use the ratio to find the moles of the other chemical

Use these moles to find its mass

Substance X

Substance Y

Ratio

Mass

Mr

Moles

first

CH₄ + 2O₂ --> CO₂ + 2H₂O

Put in the stuff we know

Match

Match the following

• Ratio

• Mass of H₂O

• Mr of H₂O

• O₂

• Mass of O₂

1:1

10

18

32

Unkn

• 1:1

• 10

• 18

• 32

• Unkn

GCSE - calculation of reacting masses
worksheet

Imagine

You are making cheese burgers

Buns come in packs of 4

Cheese comes in packs of 6

Burgers come in packs of 5

How many (single) cheeseburgers
can you make? Why?

What is limiting you?
What have you got leftover?

Limiting and Excess

•If we have more of one reactant than another it is called in
excess

•The reactant that there is less of is called the limiting reactant