1.
Fats and vegetable oils are triesters of glycerol with fatty acids. Many of these acids contain 18
carbon atoms. The table shows the relative percentages of various C18 fatty acid chains in four common
fats and oils.
(a)
Fat/Oil
C17H35COO–
/%
C17H33COO–
/%
C17H31COO–
/%
C17H29COO–
/%
Tallow
52
44
3
1
Linseed Oil
5
32
18
45
Olive Oil
2
83
15
0
Peanut Oil
7
47
46
0
Deduce which fat or oil from the table could best be described as:
saturated
......................................................................................................................................
mono-unsaturated
......................................................................................................................................
poly-unsaturated.
......................................................................................................................................
(2)
(b)
(i)
Explain the meaning of the term shelf life and suggest which fat or oil from the table
would have the shortest shelf life.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
Describe two ways in which shelf life could be increased.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 6 marks)
2.
(a)
State the conditions required for the hydrogenation of unsaturated oils.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(2)
(b)
Hydrogenation can result in the formation of trans fatty acids. Outline the meaning of the term
trans fatty acids and explain why their formation is undesirable.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(2)
(Total 4 marks)
3.
One property of foods that affects their desirability is their colour.
(i)
State the difference between a dye and a pigment.
......................................................................................................................................
......................................................................................................................................
(1)
(ii)
Explain, in terms of their effect on light, why these compounds are coloured.
......................................................................................................................................
......................................................................................................................................
(1)
(Total 2 marks)
4.
Many food items contain genetically modified ingredients.
(a)
Explain what is meant by the term genetically modified food.
......................................................................................................................................
......................................................................................................................................
(1)
(b)
Describe two advantages and one concern about the use of genetically modified food.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(3)
(Total 4 marks)
5.
Distinguish between a food and a nutrient .
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
(Total 2 marks)
6.
Explain the chemistry behind the non-enzymatic browning reaction that occurs when making
fudge from sugar and cream.
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
(Total 3 marks)
7.
State three characteristic features of all monosaccharide molecules.
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
(Total 3 marks)
8.
Which statements describe the action of a catalyst?
I.
It does not alter the ∆H for a reaction.
II.
It increases the Ea for the reaction.
III.
It alters the mechanism (pathway) of a reaction.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
9.
Consider the reaction between gaseous iodine and gaseous hydrogen.
I2(g) + H2(g)
2HI(g) ∆HO = –9 kJ
Why do some collisions between iodine and hydrogen not result in the formation of the
product?
A.
The I2 and H2 molecules do not have sufficient energy.
B.
The system is in equilibrium.
C.
The temperature of the system is too high.
D.
The activation energy for this reaction is very low.
(Total 1 mark)
10.
At 25 °C, 200 cm3 of 1.0 mol dm–3 nitric acid is added to 5.0 g of magnesium powder. If the
experiment is repeated using the same mass of magnesium powder, which conditions will result in the
same initial reaction rate?
Volume of HNO3 / cm3
Concentration of
HNO3 / mol dm–3
Temperature / °C
A.
200
2.0
25
B.
200
1.0
50
C.
100
2.0
25
D.
100
1.0
25
(Total 1 mark)
11.
Factors that affect the rate of a chemical reaction include particle size, concentration of
reactants and the temperature of the reaction.
(i)
Define the term rate of a chemical reaction.
......................................................................................................................................
......................................................................................................................................
(1)
(ii)
List the three characteristic properties of reactant particles which affect the rate of reaction as
described by the collision theory.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(3)
(Total 4 marks)
12.
Under which conditions will the reaction between 1.0 g calcium carbonate and excess
hydrochloric acid be the fastest? Assume that all reactions are carried out at the same temperature.
A.
One large piece of calcium carbonate and 2 mol dm–3 hydrochloric acid
B.
One large piece of calcium carbonate and 1 mol dm–3 hydrochloric acid
C.
Powdered calcium carbonate and 2 mol dm–3 hydrochloric acid
D.
Powdered calcium carbonate and 1 mol dm–3 hydrochloric acid
(Total 1 mark)
13.
(a)
A solution of hydrogen peroxide, H2O2, is added to a solution of sodium iodide, NaI,
acidified with hydrochloric acid, HCl. The yellow colour of the iodine, I2, can be used to determine the
rate of reaction.
H2O2(aq) + 2NaI(aq) + 2HCl(aq) → 2NaCl(aq) + I2(aq) + 2H2O(l)
The experiment is repeated with some changes to the reaction conditions. For each of the
changes that follow, predict, stating a reason, its effect on the rate of reaction.
(i)
The concentration of H2O2 is increased at constant temperature.
(2)
(ii)
The solution of NaI is prepared from a fine powder instead of large crystals.
(2)
(b)
Explain why the rate of a reaction increases when the temperature of the system increases.
(3)
(Total 7 marks)
14.
The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown
below.
2NO2(g)
N2O4(g) Kc = 0.01
What happens when the volume of a mixture at equilibrium is decreased at a constant
temperature?
I.
The value of Kc increases
II.
More N2O4 is formed
[ NO 2 ]
[N 2 O 4 ]
III.
The ratio of
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
decreases
(Total 1 mark)
15.
gas.
Methanol may be produced by the exothermic reaction of carbon monoxide gas and hydrogen
CO(g) + 2H2(g)
(a)
CH3OH(g) ∆HO = –103 kJ
State the equilibrium constant expression, Kc, for the production of methanol.
......................................................................................................................................
......................................................................................................................................
(1)
(b)
State and explain the effect of changing the following conditions on the amount of methanol
present at equilibrium:
(i)
increasing the temperature of the reaction at constant pressure.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
increasing the pressure of the reaction at constant temperature.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(c)
The conditions used in industry during the production of methanol are a temperature of 450 °C
and pressure of up to 220 atm. Explain why these conditions are used rather than those that could give
an even greater amount of methanol.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(2)
(d)
A catalyst of copper mixed with zinc oxide and alumina is used in industry for this production of
methanol. Explain the function of the catalyst.
......................................................................................................................................
......................................................................................................................................
(1)
(Total 8 marks)
16.
What is the equilibrium constant expression, Kc, for the following reaction?
N2O4(g)
A.
B.
Kc =
[NO 2 ]
[N 2 O 4 ]
Kc =
[NO 2 ] 2
[N 2 O 4 ]
2NO2(g)
[NO 2 ]
C.
2
Kc = [N 2 O 4 ]
D.
Kc = [NO2][N2O4]2
(Total 1 mark)
17.
The Haber process enables the large-scale production of ammonia needed to make fertilizers.
The equation for the Haber process is given below.
N2(g) + 3H2
2NH3(g)
The percentage of ammonia in the equilibrium mixture varies with temperature.
(i)
Use the graph to deduce whether the forward reaction is exothermic or endothermic and
explain your choice.
(2)
(ii)
State and explain the effect of increasing the pressure on the yield of ammonia.
(2)
(iii)
Explain the effect of increasing the temperature on the rate of reaction.
(2)
(Total 6 marks)
18.
Nicotine and caffeine are commonly classified as stimulants.
(a)
State the name of one functional group which is present in caffeine but absent in nicotine.
......................................................................................................................................
......................................................................................................................................
(1)
(b)
Other than methyl groups, state the name of one functional group present in both caffeine and
nicotine.
......................................................................................................................................
......................................................................................................................................
(1)
(Total 2 marks)
19.
(a)
Explain why the relative atomic mass of argon is greater than the relative atomic mass
of potassium, even though the atomic number of potassium is greater than the atomic number of argon.
......................................................................................................................................
......................................................................................................................................
(1)
(b)
Deduce the numbers of protons and electrons in the K+ ion.
......................................................................................................................................
(1)
(c)
Deduce the electron arrangement for the K+ ion.
......................................................................................................................................
(1)
(Total 3 marks)
20.
(a)
Define the term relative atomic mass (Ar).
(1)
(b)
Relative atomic masses are obtained using a mass spectrometer. Draw a simple annotated
diagram of the mass spectrometer.
(5)
(Total 6 marks)