INTRODUCTORY CHEMISTRY

Year 10 C Pathway

Mr. D. Patterson

Outcomes

Calculate the percentage composition of elements in compounds.

Calculate the percentage composition of water in hydrated compounds.

Calculate the mass composition of the constituents in a given quantity of a compound and vice versa.

What’s in a cake?

What percentage of the total mass is made up of milk?

Ingredient Mass (one) Quantity Total Mass

Egg 48 g 2 96 g

Milk 268 g 1 268 g

Flour 290 g 2 580 g

TOTAL 944 g

What’s in a cake?Ingredient Mass (one) Quantity Total Mass

Egg 48 g 2 96 g

Milk 268 g 1 268 g

Flour 290 g 2 580 g

TOTAL 944 g

Percentage composition

The percentage composition of a chemical compound is a measure of the relative mass of each of the different elements/ions/molecules in that compound

Percentage Composition

To determine the percentage of an element in a compound:

Example Problem

What percentage of sulfuric acid is oxygen?

Elements Mass (Ar) Quantity Total Mass

H 1 2 2

S 32.1 1 32.1

O 16 4 64

Total (Mr) 98.1

Example Problem 2

What percentage of water is found in hydrated zinc chloride?

Outcomes

Calculate the percentage composition of elements in compounds.

Calculate the percentage composition of water in hydrated compounds.

Calculate the mass composition of the constituents in a given quantity of a compound and vice versa.

Checkpoint 8.4, 8.5 Sets 14