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PHYSICAL SCIENCES CHEMISTRY JULY 2021 ASSESSMENT

Last updated 10 months ago
50 questions
Note from the author:
2 HOURS - 100 MARKS
Wherever the question requires you to use the "show your work" feature, you must answer the question on paper. DO NOT COMPLETE THESE QUESTIONS ON FORMATIVE.
At the end of the assessment you will attach a scanned pdf of your written answers to the assignment in Google classroom.
2 HOURS - 100 MARKS
Wherever the question requires you to use the "show your work" feature, you must answer the question on paper. DO NOT COMPLETE THESE QUESTIONS ON FORMATIVE.
At the end of the assessment you will attach a scanned pdf of your written answers to the assignment in Google classroom.

SECTION A: ORGANIC CHEMISTRY (30 Marks)

1

Which one of the following will rapidly decolourise bromine water?

2

Identify the two reactants needed to make ethyl butanoate

Organic reactions

Consider the flow diagram showing how an alcohol (compound P) can be used to prepare other organic compounds. The letters A - F represent different organic rections. X, Y and Z are organic compounds.

1

Identify the functional group of Compound P.

12

Identify the general type of reaction and the specific type of reaction occuring for A - F

  • ADDITION
  • SUBSTITUTION
  • ELIMINATION
  • CONDENSATION
  • Halogenation
  • Hydration
  • Hydrohalogenation
  • Dehydrohalogenation
  • Dehydration
  • Hydrolysis
  • Dehalogenation
  • Hydrogenation
  • Dehydrogenation
  • No special name
  • Reaction A
  • Reaction B
  • Reaction C
  • Reaction D
  • Reaction E
  • Reaction F
1

To which homologous series does compound X belong?

4

Using STRUCTURAL FORMULAE, write down the balanced equation for reaction B.

2

Write down the IUPAC name of compound X

1

Write down the molecular formula of the inorganic reactant needed for reaction D

2

Write down the IUPAC name of compound Z.

4

Using molecular formulae, write a balanced equation for the complete combustion reaction of compound P

SECTION B: ENERGY, RATES AND EQUILIBRIUM (30 Marks)

The potential energy diagram for a chemical reaction is shown below.

1

X represents the potential energy of the products formed during the reverse reaction

1

This graph could represent the change in potential energy for the following reaction:

1

This graph could represent the change in potential energy for the combustion of methane

1

The role of a catalyst in a chemical reaction is to increase the ....

Consider the following chemical reaction:
Ea (forward) = 156 kJ.mol-1
Ea (reverse) = 175 kJ.mol-1
1

Is this reaction exothermic or endothermic?

1

What is the change in enthalpy for the forward reaction in kJ.mol-1? Write only the number, no units.

1

What is the change in enthalpy for the reverse reaction in kJ.mol-1? Write only the number, no units.

2

What is the change in enthalpy for the reverse reaction in kJ? Write only the number, no units.

Consider the following chemical reaction at equilibrium in a closed container:
2

Write a Kc expression for this reaction

2

More HgO(s) is now added to the container at constant temperature. How will the forward and reverse reaction rates be affected?

  • increases
  • decreases
  • remains the same
  • Forward reaction rate
  • Reverse reaction rate
1

Now the volume of the container is decreased. How will the concentration of O2 (g) have changed once the new equilibrium has been reached?

3

Redraw and complete the following rate graph illustrating the effect of reducing the volume of the container on reaction rate as the system adjusts to reach a new equilibrium. Be sure to complete the key. (if you don't have coloured pens then use solid line and dotted line)

Chemical equilibrium 1

Consider the following concentration vs time graph:

1

Write the balanced chemical equation for the forward reaction

3

How do the rates of the forward and reverse reactions compare at the following times?

  • Forward is faster than reverse
  • Reverse is faster than forward
  • Rates are equal
  • At 5 s?
  • At 23 s?
  • At 42 s?

Chemical equilibrium 2

Carbonyl bromide, COBr2 decomposes into carbon monoxide and bromine according to the following balanced equation:
Initially COBr2(g) is sealed in a 0,5 dm3 container and heated to 80 ºC. The reaction is allowed to reach equilibrium at this temperature. The equilibrium constant for the reaction at this temperature is 0,19. At equilibrium it is found that there is 3,1 g of CO(g) in the container
8

Calculate the equilibrium concentration of the COBr2(g). Show ALL working out.

1

Which one of the following correctly describes the Kc value when the equilibrium is reached at a lower temperature?

SECTION C: ACIDS AND BASES (40 Marks)

1

Consider HSO-4 and select all the statements which apply.

1

Which one of the following solutions has the highest pH? All of the solutions have a concentration 0,1 mol.dm-3

1

Order the following Ka values in order from strongest acid to weakest acid:

  1. 0,8
  2. 1 x 10-2
  3. 1 x 10-5
  4. 2 x 10-1
  5. 1 x 101
1.5 Consider Solution A:
1

What is the concentration of hydronium ions?

1

What is the concentration of hydroxide ions?

1

What is the pH?

Consider the following equation at 25 ºC:
H2SO4 + 2H2O ⇌ SO42- + 2H3O+
1

Describe sulphuric acid as strong/weak acid/base

2

Calculate the concentration of hydronium ions if originally [H2SO4] = 0,1 mol.dm-3.

3

Hence, calculate the concentration of hydroxide ions at equilibrium.

1

What will happen to the pH if concentrated NaOH is added?

1

What will happen to the pH if water is added?

pH and Kw

Kw = [H3O+][OH-] ∆H < 0
1

In pure water [H3O+] = [OH-] at any temperature

1

At 98 º C, the Kw for water will likely be:

1

The pH of pure water at 18 ºC is closer to:

1

How will Kw be affected if a few drops of KOH is added?

Titrations

A titration is performed using hydrochloric acid of concentration 0,2 mol.dm-3 and a solution of barium hydroxide Ba(OH)2.
The apparatus used in this titration is shown below:

1

What is the name of the chemical reaction that takes place during a titration?

3

Write a balanced chemical equation for this reaction

1

Which solution is the standard solution?

1

Identify glassware A

1

Identify glassware B

1

Identify glassware C

In this laboratory procedure, 25 cm3 of the hydrochloric acid is placed into glassware B with a few drops of indicator.

The barium hydroxide is placed into glassware C. After performing an initial “rough” titration, three titration attempts are performed. The following diagrams show sections of glassware C with the initial and final readings for each attempt:

6

a) Redraw and complete the following table.
b) Calculate the average volume of barium hydroxide used.

To recap - in this titration:
Glassware B contained 25 cm3 of the hydrochloric acid of concentration 0,2 mol.dm-3
Glassware C contained the barium hydroxide solution
6

a) Calculate the number of moles of hydrochloric acid that reacted. Express answer in 4 decimal places.
b) Calculate the number of moles of barium hydroxide that reacted. Express answer to 4 decimal places
c) Calculate the concentration of the barium hydroxide solution. Express answer in 2 decimal places

2

Which titration curve best matches this titration?