Quick answer: A mole is 6.022 × 10²³ particles, and its mass in grams is the molar mass M, so n = m/M links mass to amount. This AP Chemistry test on mole concept has 8 questions worth 20 marks, to do in 40 minutes: moles of methane, mass spectrum of an element and empirical formula. The mark scheme is on a separate page; free printable PDF.
This AP Chemistry test on mole concept test works like a real class test. The mark scheme is on a separate page, so revise with the lesson first.
This test covers moles, mass spectra, formulas and mixtures. It has 8 questions worth 20 marks. A periodic table and calculator are allowed. No hints are given.
Level: AP Chemistry · Curriculum: AP Chem Unit 1
Mole concept test: the test questions
Question 1 Moles of methane (2 marks)
A cylinder holds 8.00 g of methane, CH₄ (M = 16.043 g/mol).- Calculate the amount in moles. (1 mark)
- Calculate the number of molecules. (1 mark)
Question 2 Mass spectrum of an element (3 marks)
The figure shows the mass spectrum of element Z.- State the relative abundance of the heaviest isotope. (1 mark)
- Calculate the average atomic mass using the mass numbers. (1 mark)
- Identify Z. (1 mark)
Question 3 Empirical formula (3 marks)
A compound contains 26.6 % K, 35.4 % Cr and 38.0 % O by mass. Determine its empirical formula, showing the mole ratio. (3 marks)Question 4 Molecular formula (2 marks)
A compound has empirical formula CH and molar mass 78.1 g/mol. Determine its molecular formula. (2 marks)Question 5 Iron in an ore (3 marks)
An ore is pure Fe₂O₃ (M = 159.69 g/mol, Ar(Fe) = 55.845).- Calculate the mass percent of iron. (1 mark)
- Calculate the mass of iron in 1.00 kg of ore. (2 marks)
Question 6 Why a non-integer average? (2 marks)
Explain why the average atomic mass of an element is not a whole number even though each isotope has a nearly whole-number mass. (2 marks)Question 7 Limestone in a mixture (3 marks)
A 5.00 g mixture of calcium carbonate and sand is treated with excess acid. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. The CO₂ collected has a mass of 0.880 g.- Calculate the moles of CO₂. (1 mark)
- Calculate the mass percent of CaCO₃ in the mixture (M = 100.09 g/mol). (2 marks)
Question 8 Spot the error (2 marks)
A student calculates the molar mass of Al₂(SO₄)₃ as 27 + 32 + 64 = 123 g/mol. Identify the error and give the correct value. (2 marks)
