AS-Level Chemistry: June 2016 Paper 2 PP

Question 1

Suggest one reason, other than Incomplete Combustion or Heat Transfer to the Atmosphere, why the student’s value for the Enthalpy of Combustion of Methanol is different from that in a Data book.

(1 mark)

Answer 1

Heating up Copper/Calorimeter/Container/Thermometer/Heat Capacity of Copper/Calorimeter/Thermometer not taken into account.

Question 2

The Uncertainty in each of the Temperature readings from the Thermometer in this experiment was +_0.25’C. This gave an overall Uncertainty in the Temperature rise of +_0.5’C.
Calculate the Percentage Uncertainty for the use of the Thermometer in this experiment.

(1 mark)

Answer 2

(100 * 0.5 / 38) = 1.3%

Question 3

The student said correctly that using a thermometer with an overall Uncertainty for the rise in Temperature of +_0.5’C was adequate for this experiment.
Explain why this thermometer was adequate for this experiment.

(1 mark)

Answer 3

Because Temperature Changes, and Thermometers Measure Change in Temperature.

Question 4

Octane and Isooctane can be separated in the laboratory.
Name a laboratory technique that could be used to separate Isooctane from a Mixture of Octane and Isooctane.
Outline how this technique separates Isooctane from Octane.

(3 marks)

Answer 4

-Name: (Fractional or Simple) Distillation.

-Outline:
-Isooctane has Lower BP so Boils first.
-Isooctane Condenses and Collected Separately.

Question 5

Explain, in general terms, how a Catalyst works.

(2 marks)

Answer 5

-Provides an Alternate Reaction Pathway

-With Lower Activation Energy.

Question 6

Platinum, Palladium and Rhodium are Metals used inside Catalytic Converters. A very thin layer of the Metals is used on a honeycomb ceramic support.
Explain why a thin layer is used in this way.

(2 marks)

Answer 6

-To Reduce amount of Metals needed.

-Increases the Surface Area of the Catalyst.

Question 7

Explain why determining the precise Relative Molecular Mass of Propanol and Prop-2-en-1-ol by Mass Spectrometry could not be used to distinguish between samples of these two Compounds.

(2 marks)

Answer 7

-Have the Same Molecular Formula (C3H6O)

-Identical Mr

Question 8

1,1,1-trifluoroethane (CF3CH3) is one of the Molecules that has been used as a refrigerant in place of CFCs.
Explain why 1,1,1-trifluoroethane does not lead to the depletion of the Ozone in the Upper Atmosphere.

(1 mark)

Answer 8

Does not contain Cl / Does not Release Cl.

Question 9

There are growing concerns about the use of 1,1,1-trifluoroethane as a refrigerant as it is a Greenhouse Gas that absorbs some of Earth’s Infrared Radiation.
Give one reason why bonds in Molecules such as Carbon Dioxide and 1,1,1-trifluoroethan Absorb Infrared Radiation.

(1 mark)

Answer 9

Bonds Vibrate/Stretch/Bend OR Bonds are Polar.

Question 10

Anti-bumping granules are placed in the flask when refluxing.
Suggest why these granules prevent bumping.

(1 mark)

Answer 10

Form Smaller Bubbles. Prevent Large Bubbles.

Question 11

Which of the following Compounds would form an orange-red Precipitate when
heated with Fehling’s Solution? (1)

A) CH3CH2CN
B) CH3CH2COOH
C) CH3CHO
D) CH3COCH3

Answer 11

C) CH3CHO

Question 12

Pentanenitrile can be made by Reaction of 1-bromobutane with Potassium Cyanide.
Which of these is the correct name for the mechanism of this Reaction? (1)

A) Electrophilic addition
B) Electrophilic substitution
C) Nucleophilic addition
D) Nucleophilic substitution

Answer 12

D) Nucleophilic substitution

Question 13

Propene can be made by the dehydration of propan-2-ol. What is the percentage yield when 30 g of propene (Mr = 42.0) are formed from 50 g of propan-2-ol (Mr = 60.0)?. (1)

A) 60%
B) 67%
C) 81%
D) 86%

Answer 13

D) 86%

Question 14

Sulfur dioxide (SO2) is Produced when some Fossil Fuels are burned.
Which of the following statements is true? (1)

A) Sulfur dioxide can be removed from waste gases in a power station by an acid-base reaction with calcium oxide.

B) Sulfur dioxide is insoluble in water.

C) Sulfur dioxide is a basic oxide.

D) Sulfur dioxide is an ionic compound.

Answer 14

A

Question 15

An Organic Compound is found to contain 40.0% Carbon, 6.7% Hydrogen and 53.3% Oxygen.
Which of the following Compounds could this be? (1)

A) Ethanol
B) Ethanoic Acid
C) Methanol
D) Methanoic Acid

Answer 15

B) Ethanoic Acid

Question 16

Which of the following is the General Formula of Cyclic Alkenes such as
Cyclohexene? (1)

A) CnH2n-4
B) CnH2n-2
C) CnH2n
D) CnH2n+2

Answer 16

B) CnH2n-2

Question 17

A and B React together in this Reversible Reaction.
A + 3B ⇌ C + 2D
A Mixture of 10mol of A and 10mol of B were left to reach Equilibrium. The
Equilibrium Mixture contained 4mol of B.
What is the total amount, in moles, of Substances in the Equilibrium Mixture? (1)

A) 14
B) 16
C) 18
D) 20

Answer 17

C) 18

Question 18

The Mr of hydrated copper Sulfate (CuSO4.5H2O) is 249.6. Which of the following is the mass of Hydrated Copper Sulfate required to make 50.0 cm3 of a 0.400 mol dm−3 solution? (1)

A) 3.19 g
B) 3.55 g
C) 3.71 g
D) 4.99 g

Answer 18

D) 4.99 g

Question 19

2mol of Ideal Gas X are stored in a flask of fixed Volume.
Which of the following changes would lead to the greatest increase in Pressure
inside the flask? (1)

A) Increasing the temperature from 20 °C to 200 °C

B) Adding another 1 mol of gas X into the flask at fixed temperature

C) Adding 0.5 mol of argon gas and increasing the temperature
from 20 °C to 150 °C

D) Removing 0.5 mol of gas X and increasing the temperature from 20 °C to 300 °C

Answer 19

C