AS Chemistry Paper 2 Specimen || A+ Guaranteed.
The effect of gentle heat on maleic acid is shown below.
A student predicted that the yield of this reaction would be greater than 80%. In an
experiment,10.0 g of maleic acid were heated and 6.53 g of organic product were obtained.
Is the student correct?
Justify your answer with a calculation using these data correct answers Moles of maleic acid =
10.0/116.0 = 8.62 × 10-2
mass of organic product expected = (8.62 × 10-2 ) × 98.0 = 8.45 g
% yield = 100 × 6.53/8.45
D statement that the student was NOT correct
Initial mass of spirit burner and alcohol / g 56.38
Final mass of spirit burner and alcohol / g 55.84
Initial temperature of water / °C 20.7
Final temperature of water / °C 40.8
Use the results from Table 1 to calculate a value for the enthalpy of combustion of leaf alcohol.
Give units in your answer. (The specific heat capacity of water is 4.18 J K-1 g -1) correct
answers Temperature rise = 20.1
q = 50.0 × 4.18 × 20.1 = 4201 (J) Mass of alcohol burned = 0.54 g
Mr alcohol = 100.0
∴ mol of alcohol = n = 0.54/100 = 0.0054
Heat change per mole = q/1000n
mol-1 ΔH = -778 kJ mol-1
A 50.0 g sample of water was used in this experiment. Explain how you could measure out this
mass of water without using a balance correct answers Water has a known density (of 1.0 g cm-
3) Therefore, a volume of 50.0 cm3 could be measured out
Glucose can decompose in the presence of microorganisms to form a range of products. One of
these is a carboxylic acid (Mr = 88.0) containing 40.9% carbon and 4.5% hydrogen by mass.
, Deduce the empirical and molecular formulas of the carboxylic acid formed correct answers
Percentage of oxygen by mass = 100 - 40.9 - 4.5 = 54.6
C H O % 40.9 4.5 54.6
Divide by Ar 12 1 16 = 3.41 = 4.5 = 3.41
Divide by smallest = 3.41 = 1 4.5 = 1.32 3.41 = 1 3.41 3.41 3.41
Nearest whole number ratio = 1 × 3 1.32 × 3 1 × 3 = 3 : 3.96 : 3 Nearest integer ratio = 3 : 4 : 3
Empirical formula C3H4O3
Empirical formula mass = 88 = molecular formula mass
Therefore, molecular formula is same as the empirical formula - C3H4O3
Ethanol is formed by the fermentation of glucose. A student carried out this fermentation
reaction in a beaker using an aqueous solution of glucose at a temperature of 25 °C in the
presence of yeast. Write an equation for the reaction occurring during fermentation. correct
answers C6H12O6 ----> 2C2H5OH + 2CO2
The method used by the student in Question 4.2 would result in the ethanol being contaminated
by ethanoic acid. How does this contamination occur? correct answers Air gets in / oxidation
occurs
Identify the condition that causes a bond in CCl4 to break in the upper atmosphere. Deduce an
equation for the formation of the reactive species. correct answers UV light
CCl 4 ----> CCl3● + ●Cl
One of the reactive species formed from CCl4 acts as a catalyst in the decomposition of ozone.
Write two equations to show how this species acts as a catalyst. correct answers Cl ● + O3 ----->
ClO● + O2
ClO● + O3 ----> Cl● + 2O2
A small amount of the freon CF3Cl with a mass of 1.78 × 10-4 kg escaped from a refrigerator,
into a room of volume 100 m3 .
Assuming that the freon is evenly distributed throughout the air in the room, calculate the
number of freon molecules in a volume of 500 cm3 .
Give your answer to the appropriate number of significant figures.
The Avogadro constant = 6.02 × 1023 mol -1 correct answers Mr of CF3Cl = 104.5
The effect of gentle heat on maleic acid is shown below.
A student predicted that the yield of this reaction would be greater than 80%. In an
experiment,10.0 g of maleic acid were heated and 6.53 g of organic product were obtained.
Is the student correct?
Justify your answer with a calculation using these data correct answers Moles of maleic acid =
10.0/116.0 = 8.62 × 10-2
mass of organic product expected = (8.62 × 10-2 ) × 98.0 = 8.45 g
% yield = 100 × 6.53/8.45
D statement that the student was NOT correct
Initial mass of spirit burner and alcohol / g 56.38
Final mass of spirit burner and alcohol / g 55.84
Initial temperature of water / °C 20.7
Final temperature of water / °C 40.8
Use the results from Table 1 to calculate a value for the enthalpy of combustion of leaf alcohol.
Give units in your answer. (The specific heat capacity of water is 4.18 J K-1 g -1) correct
answers Temperature rise = 20.1
q = 50.0 × 4.18 × 20.1 = 4201 (J) Mass of alcohol burned = 0.54 g
Mr alcohol = 100.0
∴ mol of alcohol = n = 0.54/100 = 0.0054
Heat change per mole = q/1000n
mol-1 ΔH = -778 kJ mol-1
A 50.0 g sample of water was used in this experiment. Explain how you could measure out this
mass of water without using a balance correct answers Water has a known density (of 1.0 g cm-
3) Therefore, a volume of 50.0 cm3 could be measured out
Glucose can decompose in the presence of microorganisms to form a range of products. One of
these is a carboxylic acid (Mr = 88.0) containing 40.9% carbon and 4.5% hydrogen by mass.
, Deduce the empirical and molecular formulas of the carboxylic acid formed correct answers
Percentage of oxygen by mass = 100 - 40.9 - 4.5 = 54.6
C H O % 40.9 4.5 54.6
Divide by Ar 12 1 16 = 3.41 = 4.5 = 3.41
Divide by smallest = 3.41 = 1 4.5 = 1.32 3.41 = 1 3.41 3.41 3.41
Nearest whole number ratio = 1 × 3 1.32 × 3 1 × 3 = 3 : 3.96 : 3 Nearest integer ratio = 3 : 4 : 3
Empirical formula C3H4O3
Empirical formula mass = 88 = molecular formula mass
Therefore, molecular formula is same as the empirical formula - C3H4O3
Ethanol is formed by the fermentation of glucose. A student carried out this fermentation
reaction in a beaker using an aqueous solution of glucose at a temperature of 25 °C in the
presence of yeast. Write an equation for the reaction occurring during fermentation. correct
answers C6H12O6 ----> 2C2H5OH + 2CO2
The method used by the student in Question 4.2 would result in the ethanol being contaminated
by ethanoic acid. How does this contamination occur? correct answers Air gets in / oxidation
occurs
Identify the condition that causes a bond in CCl4 to break in the upper atmosphere. Deduce an
equation for the formation of the reactive species. correct answers UV light
CCl 4 ----> CCl3● + ●Cl
One of the reactive species formed from CCl4 acts as a catalyst in the decomposition of ozone.
Write two equations to show how this species acts as a catalyst. correct answers Cl ● + O3 ----->
ClO● + O2
ClO● + O3 ----> Cl● + 2O2
A small amount of the freon CF3Cl with a mass of 1.78 × 10-4 kg escaped from a refrigerator,
into a room of volume 100 m3 .
Assuming that the freon is evenly distributed throughout the air in the room, calculate the
number of freon molecules in a volume of 500 cm3 .
Give your answer to the appropriate number of significant figures.
The Avogadro constant = 6.02 × 1023 mol -1 correct answers Mr of CF3Cl = 104.5
