# Relative formula mass (HT only)

This lesson will recap briefly on relative atomic mass and students will calculate relative formula mass and percentage composition of an element in a compound. Students will also be able to work backwards and work out the mass and name of a metal in a compound using the relative formula mass.

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.The formula of sodium chloride is NaCl. Calculate the relative formula mass of sodium chloride. Relative atomic masses: Na = 23; Cl = 35.5

1/5

Q2.The formula of magnesium sulfate is MgSO₄. Calculate the relative formula mass of magnesium sulfate. Relative atomic masses: Mg = 24; S= 32; O = 16.

2/5

Q3.Calculate the relative formula mass of iron oxide, Fe₂O₃. Relative atomic masses: O = 16; Fe = 56.

3/5

Q4.A chemist was asked to identify a nitrogen compound. The chemist carried out an experiment to find the relative formula mass (Mr) of the compound. The Mr of the compound was 44. Relative atomic masses: N = 14; O = 16. What is the formula of the compound?

4/5

Q5.Calculate the percentage of O in Be(OH)₂. Be = 9; O = 16; H = 1.

5/5

Quiz:

# Intro quiz - Recap from previous lesson

Before we start this lesson, let’s see what you can remember from this topic. Here’s a quick quiz!

Q1.The formula of sodium chloride is NaCl. Calculate the relative formula mass of sodium chloride. Relative atomic masses: Na = 23; Cl = 35.5

1/5

Q2.The formula of magnesium sulfate is MgSO₄. Calculate the relative formula mass of magnesium sulfate. Relative atomic masses: Mg = 24; S= 32; O = 16.

2/5

Q3.Calculate the relative formula mass of iron oxide, Fe₂O₃. Relative atomic masses: O = 16; Fe = 56.

3/5

Q4.A chemist was asked to identify a nitrogen compound. The chemist carried out an experiment to find the relative formula mass (Mr) of the compound. The Mr of the compound was 44. Relative atomic masses: N = 14; O = 16. What is the formula of the compound?

4/5

Q5.Calculate the percentage of O in Be(OH)₂. Be = 9; O = 16; H = 1.

5/5

# Video

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# Worksheet

These slides will take you through some tasks for the lesson. If you need to re-play the video, click the ‘Resume Video’ icon. If you are asked to add answers to the slides, first download or print out the worksheet. Once you have finished all the tasks, click ‘Next’ below.

Quiz:

# Relative formula mass

This quiz will test your knowledge form this lesson

Q1.The formula of sodium chloride is NaCl. Calculate the relative formula mass of sodium chloride. Relative atomic masses: Na = 23; Cl = 35.5

1/5

Q2.Calculate the relative formula mass of iron oxide, Fe₂O₃. Relative atomic masses: O = 16; Fe = 56.

2/5

Q3.Calculate the percentage of O in Be(OH)₂. Be = 9; O = 16; H = 1

3/5

Q4.A metal oxide has a relative formula mass (Mr) of 81. The formula of this metal oxide is XO. The relative atomic mass (Ar) of oxygen is 16. Calculate the relative atomic mass (Ar) of metal X.

4/5

Q5.What is the name of the metal X (from the question above)?

5/5

Quiz:

# Relative formula mass

This quiz will test your knowledge form this lesson

Q1.The formula of sodium chloride is NaCl. Calculate the relative formula mass of sodium chloride. Relative atomic masses: Na = 23; Cl = 35.5

1/5

Q2.Calculate the relative formula mass of iron oxide, Fe₂O₃. Relative atomic masses: O = 16; Fe = 56.

2/5

Q3.Calculate the percentage of O in Be(OH)₂. Be = 9; O = 16; H = 1

3/5

Q4.A metal oxide has a relative formula mass (Mr) of 81. The formula of this metal oxide is XO. The relative atomic mass (Ar) of oxygen is 16. Calculate the relative atomic mass (Ar) of metal X.

4/5

Q5.What is the name of the metal X (from the question above)?

5/5

# Lesson summary: Relative formula mass (HT only)

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