1. How many molecules are present in a drop of
ethanol, C2H5OH, of mass 2.3 × 10–3 g? (L =
6.0 × 1023 mol–1)
A. 3.0 × 10 19
B. 3.0 × 1020
C. 6.0 × 1020
D. 6.0 × 1026
(Total 1 mark)
2. Which sample has the greatest mass?
A. 1 mol of SO2
B. 2 mol of N2O
C. 2 mol of Ar
D. 4 mol of NH3
(Total 1 mark)
3. What is the total number of hydrogen atoms in
1.0 mol of benzamide, C6H5CONH2?
A. 7
B. 6.0 × 1023
C. 3.0 × 1024
D. 4.2 × 1024
(Total 1 mark)
4. What is the total number of nitrogen atoms in
two mol of NH4NO3?
A. 4
B. 6.02 × 1023
C. 1.20 × 1024
D. 2.41 × 1024
(Total 1 mark)
5. Which sample has the greatest mass?
A. 6.0 × 1025 molecules of hydrogen
B. 5.0 mol of neon atoms
C. 1.2 × 1024 atoms of silver
D. 1.7 × 102 g of iron
(Total 1 mark)
6. Which is both an empirical and a molecular
formula?
A. C5H12
B. C5H10
C. C4H8
D. C4H10
(Total 1 mark)
7. What is the approximate molar mass, in g
mol–1, of MgSO4•7H2O?
A. 120
B. 130
C. 138
D. 246
(Total 1 mark)
8. The relative molecular mass of a gas is 56 and
its empirical formula is CH2. What is the
molecular formula of the gas?
A. CH2
B. C2H4
C. C3H6
D. C4H8
(Total 1 mark)
9. On analysis, a compound with molar mass 60 g
mol–1 was found to contain 12 g of carbon, 2 g
of hydrogen and 16 g of oxygen. What is the
molecular formula of the compound?
A. CH2O
B. CH4O
C. C2H4O
D. C2H4O2
(Total 1 mark)
10. 4.00 mol of a hydrocarbon with an empirical
formula of CH2 has a mass of 280 g. What is
the molecular formula of this compound?
A. C2H4
B. C3H6
C. C4H8
D. C5H10
(Total 1 mark)
11. Smog is common in cities throughout the
world. One component of smog is PAN
(peroxyacylnitrate) which consists of 20.2 % C,
11.4 % N, 65.9 % O and 2.50 % H by
mass. Determine the empirical formula of
PAN, showing your working.
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(Total 3 marks)