This is a check-up, not a test: 16 quick questions across the five GCSE skills that A-Level Chemistry assumes from day one — maths, formulae, moles, practical skills and atomic structure. You get one attempt per question, and every answer is explained as you go.
At the end you'll see a skill-by-skill breakdown and which modules to start with. Your results stay in this browser — nothing is sent anywhere, no sign-up.
Which of these is 0.00052 in standard form? Tick (✓) one box.
Round 0.030456 to 3 significant figures. Tick (✓) one box.
Convert 250 cm3 to dm3.
Worked steps
- 1 dm3 = 1000 cm3
- 250 ÷ 1000 = 0.250 dm3
Rearrange c = n ÷ V to make V the subject. Tick (✓) one box.
Type the formula of aluminium oxide.
- Al3+ and O2− — the charges aren't equal, so it's not 1:1. Cross them over.
- Crossed the wrong way: 2 × Al3+ balances 3 × O2−.
Why
- Al3+ and O2− → Al2O3 (6+ balances 6−).
What is the formula of calcium nitrate? Tick (✓) one box.
Balance: __Al + __O2 → __Al2O3. Tick (✓) one box.
Calculate the Mr of Mg(OH)2. Ar: Mg 24.3, O 16.0, H 1.0.
Worked steps
- Bracket first: (16.0 + 1.0) = 17.0
- 24.3 + 2 × 17.0
- = 58.3
How many moles of Na2CO3 are in 5.3 g? Mr = 106.0.
Worked steps
- n = m ÷ Mr
- 5.3 ÷ 106.0
- = 0.050 mol
What mass is 0.30 mol of CaCO3? Mr = 100.1.
Worked steps
- m = n × Mr
- 0.30 × 100.1 = 30.0 g
0.40 mol of solute is dissolved to make 250 cm3 of solution. Calculate the concentration in mol/dm3.
Worked steps
- V = 250 ÷ 1000 = 0.250 dm3
- c = n ÷ V = 0.40 ÷ 0.250
- = 1.6 mol/dm3
A reaction has a theoretical yield of 8.0 g. The actual yield is 6.0 g. Calculate the percentage yield.
Worked steps
- % yield = actual ÷ theoretical × 100
- 6.0 ÷ 8.0 × 100 = 75%
A measuring cylinder has a maximum error of ±0.5 cm3. Calculate the percentage error when measuring 25.0 cm3.
Worked steps
- % error = error ÷ measured × 100
- 0.5 ÷ 25.0 × 100 = 2.0%
Two different students, using different equipment, get very similar results. The results are best described as… Tick (✓) one box.
How many electrons are in a Mg2+ ion? Mg has atomic number 12. Tick (✓) one box.
At GCSE you learned shells fill 2, 8, 8. How many electrons can the third shell actually hold? Tick (✓) one box.
Your results
How to read this: "Start here" and "Shaky" skills are where the marks are hiding — work those modules first, 15–25 minutes each, then retake this diagnostic in the last week of the holidays.
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