Examples of Questions

Percentage Composition

Gravimetric Analysis

Some ionic compounds have water molecules inside their crystals. These are called hydrated salts. We can use the mass of the hydrated salt, and the mass of the anhydrous salt (after "cooking" all of the water out of it) to find the formula of the hydrated salt:

Hydrated Barium Chloride

We put this theory into practice, trying to find the formula of hydrated barium chloride.

SOURCE: Wignall and Wales, Beginning Chemistry

Mole Calculations

Now we know a bit about molar mass and amount, we can put this all together:

Molar Mass

Molar mass is the link between amount and mass. We will learn how to use this tomorrow, but today we had to find the molar mass of different molecules and compounds:

The Mole

Today we started going through the details of the last lesson in more detail:

There are good notes on pp73-74 in our books.

Formula	# of Each Atom	Amount of Substance (mol)	Amount of Each Atom (mol)
CuSO4	1 Cu 1 S 4 O	0.20	0.20 Cu 0.20 S 0.80 O
Al2O3		0.55
Ba(NO3)2		0.15
CH3OH		0.40
Na2CO3.H2O		0.50

Introduction to Stoichiometry

Today was an overview of the relationship between atomic mass, molar mass, mass and amount. We were introduced to how we use the Periodic Table and Balanced Equations to work out how much of each reagent we need (measured in moles).

Given the mass of one of the reagents, what is the mass of the molecules/compounds that have question marks beneath them?

Balancing Equations

Before we can balance equations, we need to know what the products are:

Once we have the products, it is a case of practice, practice, practice to get it right. There are a few tricks though.

The Periodic Table