Section 3 - Equations, calculations and electrolysis

Question 1

How do you work out Mr value (Relative formula mass)

Answer 1

The Ar of the atoms added together

Question 2

What is a mole?

Answer 2

6.02x10^23 (602 000 000 000 000 000 000 000)

Question 3

Define the molar mass

Answer 3

The mass of one mole

Question 4

What is the formula for working out the number of moles?

Answer 4

Mass/Mr

Question 5

What is the formula for working out the mass of an element of compound?

Answer 5

Number of moles x Mr

Question 6

What is the formula for working out the Mr?

Answer 6

Mass/Number of moles

Question 7

What is the method to calculating the amount of product from a mass of reactant?

Answer 7

1) Write a balanced equation

2) Work out relative formula masses (Mr) of the reactant and product

3) Find out how many moles there are of substances you know the mass of

4) Used 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 8

What is the empirical formula?

Answer 8

The smallest whole number ratio of atoms in a compound

Question 9

How do you work out empirical formula?

Answer 9

1) List all of the elements in the compounds

2) Write down their masses

3) Find the number of moles by dividing each mass by the relative atomic mass for that element

4) Turn these numbers into a ratio by dividing by the smallest number of moles

5) Get the ratio in its simplest whole number form

Question 10

How do you work out the molecular formula from the empirical formula?

Answer 10

1) Find the mass of the empirical formula

2) Divide the relative molecular mass of the empirical formula by the mass of the empirical formula

3) Multiply each atom of the element by that number