Akwankyerɛ

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?

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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.

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1

Identify the functional group of Compound P.

12

1

To which homologous series does compound X belong?

4

2

1

2

4

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

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

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1

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

Nokorɛ

Ɛnyɛ ampa

1

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

Nokorɛ

Ɛnyɛ ampa

1

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

activation energy

heat of reaction

rate of the reaction

yield

Consider the following chemical reaction:

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E_a (forward) = 156 kJ.mol_^-1

E_a (reverse) = 175 kJ.mol_^-1

1

Is this reaction exothermic or endothermic?

exothermic

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

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

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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

3

Chemical equilibrium 1

Consider the following concentration vs time graph:

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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, COBr_² decomposes into carbon monoxide and bromine according to the following balanced equation:

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Initially COBr₂(g) is sealed in a 0,5 dm_³ 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 K_c value when the equilibrium is reached at a lower temperature?

K_c > 0,19

K_c < 0,19

K_c = 0,19

SECTION C: ACIDS AND BASES (40 Marks)

1

Consider HSO^-₄and 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

Na₂CO₃(aq)

HNO₃(aq)

NH₄Cl(aq)

CH₃COOH

1

Order the following K_avalues in order from strongest acid to weakest acid:

2 x 10^-1
1 x 10^-2
1 x 10^-5
1 x 10¹
0,8

1.5 Consider Solution A:

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1

What is the concentration of hydronium ions?

1 x 10^-2 mol.dm^-3

0,02 mol.dm^-3

1 x 10^-12 mol.dm^-3

1 x 10^-14 mol.dm^-3

1

Consider the following equation at 25 ºC:

H₂SO₄+ 2H₂O ⇌ SO₄_^2- + 2H₃O⁺

1

Describe sulphuric acid as strong/weak acid/base

strong

weak

acid

base

2

3

1

pH and K_w

K_w = [H₃O_⁺][OH_^-] ∆H < 0

1

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

Nokorɛ

Ɛnyɛ ampa

1

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:

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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

Identify glassware A

1

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:

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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 cm_³ 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

PHYSICAL SCIENCES CHEMISTRY JULY 2021 ASSESSMENT

SECTION A: ORGANIC CHEMISTRY (30 Marks)

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

SECTION C: ACIDS AND BASES (40 Marks)

PHYSICAL SCIENCES CHEMISTRY JULY 2021 ASSESSMENT

SECTION A: ORGANIC CHEMISTRY (30 Marks)

Which one of the following will rapidly decolourise bromine water?

Identify the two reactants needed to make ethyl butanoate

Organic reactions

Identify the functional group of Compound P.

To which homologous series does compound X belong?

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

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

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

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

Is this reaction exothermic or endothermic?

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

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

Write a Kc expression for this reaction

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

Chemical equilibrium 1

Write the balanced chemical equation for the forward reaction

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

Chemical equilibrium 2

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

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)

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

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

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

What is the concentration of hydronium ions?

Describe sulphuric acid as strong/weak acid/base

pH and Kw

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

Titrations

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

Write a balanced chemical equation for this reaction

Identify glassware A

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

Which one of the following will rapidly decolourise bromine water?

Identify the two reactants needed to make ethyl butanoate

Organic reactions

Identify the functional group of Compound P.

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

To which homologous series does compound X belong?

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

Write down the IUPAC name of compound X

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

Write down the IUPAC name of compound Z.

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

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

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

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

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

Is this reaction exothermic or endothermic?

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

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

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

Write a Kc expression for this reaction

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

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

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

Write the balanced chemical equation for the forward reaction

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

Chemical equilibrium 2

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

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

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

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

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

What is the concentration of hydronium ions?

What is the concentration of hydroxide ions?

What is the pH?

Describe sulphuric acid as strong/weak acid/base

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

Hence, calculate the concentration of hydroxide ions at equilibrium.

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

What will happen to the pH if water is added?

pH and Kw

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

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

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

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

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

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

Order the following K_avalues in order from strongest acid to weakest acid:

pH and K_w

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

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

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

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

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

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

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

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

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

Order the following K_avalues in order from strongest acid to weakest acid:

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

pH and K_w

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

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

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

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

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

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

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

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