SC9

Question 1

What is the molecular formula?

Answer 1

The exact number of each type of atom in a compound.

E.g - carbon dioxide = CO2 / hydrogen chloride = HCL

Question 2

What is the relative formula mass?

Answer 2

Mr of a compound - its the relative atomic masses (Ar) of all the atoms in its formula added together.

Question 3

What’s the empirical formula?

Answer 3

The simplest whole number ratio of each type of atom in a compound.

E.g - C6H12O6 = CH2O - empirical formula of glucose.

Question 4

What is a mole?

Answer 4

1 mole of any substance is equal to the Ar or Mr in grams.

Question 5

What are the equations for moles?

Answer 5

Mass = moles X Ar/Mr

Moles = concentration X volume

Question 6

How can you calculate the amount of product from the limiting reactant?

Answer 6

1. Write out a balanced equation.
2. Work out relative formula masses (Mr) of the reactant and product you’re interested in.
3. Find out how many moles there are of the substance you know the mass of.
4. Use the balanced equation to work out how many moles there’ll be of the other substance.
5. Use the number of moles to calculate the mass.

Question 7

What is the limiting reactant?

Answer 7

The reactant that’s used up in a reaction, because it limits the amount of product that’s formed.

Question 8

What happens to the mass in a chemical reaction?

Answer 8

Its always conserved.

Question 9

Why would the mass change?

Answer 9

Hasn’t all reacted
If gas gets in and reacts.
If gas leaves, the mass will decrease.