Cambridge Checkpoints 2010 – Exam style questions
Q1. Analysis of a hydrocarbon shows it contains 4.50 g of Carbon and 1.00 g of Hydrogen.
The empirical formula of the hydrocarbon is
A. CH3
B. C2H9
C. C3H8
D. C9H2
Q2. One molecule of butane (C4H10) would have a mass, in grams, of
A.
58
6×1023
B. 58 x 6 x 1023
C. 58
D.
6×1023
58
Q3. A pure hydrocarbon is burnt in pure oxygen. The products are carbon dioxide (1.76 g)
and water (1.08 g). The empirical formula of the hydrocarbon is
A. CH2
B. CH3
C. C2H3
D. CH4
Q4. Ammonium Nitrate, NH4NO3, is often used as a source of nitrogen for plants since it is
soluble in water. What mass of nitrogen, in grams, is contained in 1.0 Kg of ammonium
nitrate?
A. 175
B. 225
C. 350
D. 775
Q5. Compounds of arsenic are often used as pesticides. The arsenic content of a pesticide
can be determined by dissolving the pesticide in a suitable solvent and precipitating the
arsenic as arsenic sulfide, As2S3. If 0.312 g of arsenic sulfide can be obtained from 2.25 g of
pesticide then the percentage of arsenic in the pesticide is closest to:
A. 4.23
B. 8.45
C. 13.90
D. 61.0
Q6. 0.10 mole of C4H9OH reacts completely with molecular oxygen, O2. The number of mole
of oxygen molecules used is
A. 0.50
B. 0.55
C. 0.60
D. 0.65
Q7. Hydrogen and Chlorine react according to the equation:
𝐻2 (𝑔) +
𝐶𝑙2 (𝑔) → 2𝐻𝐶𝑙 (𝑔)
3 mole of H2 and 2 mole of Cl2 are placed in a vessel and sealed. When reaction is complete
the vessel will contain
A. 5 mole of HCl
B. 6 mole of HCl and 1 mole of Cl2
C. 4 mole of HCl and 1 mole of Cl2
D. 4 mole of HCl and 1 mole of H2
Q8. An organic compound is known to contain only carbon, hydrogen and oxygen. The
compound contains, by mass, 39.1% of carbon and 8.7% of hydrogen. The number of carbon
atoms in the empirical formula is
A. 1
B. 2
C. 3
D. 4
Q9. Xylose is a compound that has five carbon atoms in each molecule and contains 40% by
mass. What is the molar mass of xylose?
A. 30
B. 67
C. 150
D. It cannot be determined without further information
Q10 and 11 refer to the following information:
The amount of Calcium carbonate (CaCO3) in the ore dolomite can be determined by
gravimetric analysis. The dolomite sample is dissolved in acid and the calcium ions (Ca2+)
present are precipitated as Calcium oxalate (CaC2O4). The calcium oxalate is filtered, dried
and strongly heated to form calcium oxide (CaO).
Molar masses are: CaCO3 = 100.1; CaC2O4 = 128.1 and CaO = 56.1
Q10. In one analysis the mass of dolomite used was 3.72 g. The mass of calcium oxide
formed was found to be 1.24 g. The percentage of calcium carbonate in the dolomite
sample is closest to
A. 26.0
B. 33.3
C. 56.0
D. 59.5
Q11. Two possible sources of error in this analysis are:
I – the precipitate of calcium oxalate is not rinsed with water after being filtered
II – the calcium oxide is not heated to constant mass
Which of these two errors, if any, would lead to a result that is too high?
A. I only
B. II only
C. Both I and II
D. Neither I nor II
Q12. When 2.54 g of solid iodine reacts with excess chlorine and the unreacted chlorine is
evaporated, 4.67 g of a yellow product remains. The empirical formula of the product is
A. ICl2
B. ICl3
C. ICl4
D. ICl5
Q13. A sample of fertiliser was analysed and found to contain 80% by mass of ammonium
nitrate (NH4NO3) and 20% by mass of potassium chloride (KCl). The mass of nitrogen in a
1.00 Kg packet of the fertiliser is
A. 140 g
B. 175 g
C. 280 g
D. 350 g
Q14. Many garden fertilisers contain sulfate ion as one of their components. Gravimetric
analysis can be used to determine the soluble sulfate content as follows. A 2.50 g sample of
a fertiliser was dissolved in water. Barium sulfate was precipitated by adding Barium
chloride solution. The relevant equation is
𝐵𝑎2+ (𝑎𝑞) + 𝑆𝑂42+ (𝑎𝑞) → 𝐵𝑎𝑆𝑂4 (𝑠)
The precipitate was filtered, washed, dried and had a mass of 0.566 g.
a)
b)
c)
d)
Calculate the number of mole of barium sulfate precipitated
Calculate the mass of sulfate in the sample of fertiliser
What is the percentage of sulfate in the fertiliser?
If the precipitate was not thoroughly washed before it was dried, what effect would
this have on the calculated percentage of sulfate? Explain your answer.