Chemistry Paper 1 Questions and Answers - Samia Joint Mock Examination 2023

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Instructions to candidates

Answer ALL the questions
KNEC Mathematical tables and electronic calculators may be used for calculations.
All working MUST be clearly shown where necessary.
Candidates should answer the questions in English.

What is the difference between chromatography and chromatology? (1mark)
When dilute Sulphuric (VI) acid is connected in a circuit to test conduction of electricity, the bulb lights while when concentrated Sulphuric (VI) acid is used in the same set-up, the bulb does not light. Explain this observation. (2marks)
Explain why Aluminium Chloride has PH 3 when dissolved in water? (2marks)
Below is a list of substances.
Soap solution, common salt, urine, lemon juice and baking powder.
Select:
1. A substance that is likely to give a PH of 3.0 when tested? (1mark)
2. A substance (s) which is likely to resemble sodium hydrogen carbonate.(1mark)
3. Two substances when reacted are likely to give the product with same PH as that of common salt. (1mark)
Briefly explain the observation made when a small piece of sodium metal is dropped into a bowl of water. (3marks)
1. Define Le Chatelier’s principle. (1mark)
2. A fixed mass of a gas has a volume of 400cm² at 20°C, what temperature rise would produce a 10% increase in volume if the pressure remains constant. (3marks)
Using Dots (.) and (x) diagram, show the number of electrons used in bonding of H₃O⁺ (2marks)
Explain why a luminous flame appears yellow. (2marks)
Some sodium chloride was found to be contaminated with copper (II) oxide. Describe how a dry sample of sodium chloride can be separated from the mixture. (2marks)
Hot platinum wire was lowered into a flask containing concentrated ammonia solutions shown below.

State and explain observations made (3marks)
Give three characteristics of gases according to Kinetic theory of matter. (3marks)
The formula below represents active ingredients of two cleansing agents A and B

Which one of the cleansing agents would be suitable to be used in water containing magnesium hydrogen carbonate? Explain. (2marks)
The set-up below was used to obtain a sample of iron

Write two equations for the reactions which occur in the combustion tube. (2marks)
The diagram below represents a set-up that can be used for the electrolysis of dilute Sulphuric acid.
1. Name the electrodes A and B (1mark)
2. Write an equation for the reaction taking place at electrode B. (1mark)
3. What happens to the concentration of dilute sulphuric acid as the reaction continues? (1mark)
Describe one physical and one chemical test that can be used to identify Ethane gas. (2marks)
15cm³of a solution containing 2.88g/dm³ of an alkali XOH completely reacts with 20cm³ of 0.045M sulphuric acid. Calculate the reactive atomic mass of X present in the alkali. (3marks)
Using equations, state and explain the changes in mass that occur when the following are heated separately in open crucible. (3marks)
1. Magnesium metal
2. Zinc carbonate
In the space provided below, draw a set-up that can be used to show the reaction between nitrogen (I) oxide with copper to give Nitrogen gas. (3marks)
The flow chart below shows some process in extraction of lead metal. Study it and answer the questions that follow;
1. Name two raw materials that were fed into Unit I (1mark)
2. State one environment hazard associated with the process in Unit I. (1mark)
3. What is the function of Coke in Unit II (1mark)
Sulphur exhibits as an allotropy.
1. What is allotropy? (1mark)
2. Name the two allotropes of sulphur. (1mark)
3. Sulphur powder was placed in a deflagrating spoon and heated on a Bunsen burner.
  1. State the observation made. (1mark)
  2. The product obtained was dissolved in water. Comment on the PH of the solution formed. (1mark)
The set-up below was used to prepare a sample of an organic compound X.
1. Identify gas X (1mark)
2. Write the equation for the reaction that produces gas X. (1mark)
3. 1 Mole of chlorine was reacted with gas X in presence of sunlight.
  1. State one observation made. (½ mark)
  2. Name the major product formed. (½ mark)
The apparatus shown below was used to investigate the effect of carbon (II) oxide on Copper (II) oxide.
1. State the observation that was made in the combustion tube at the end of the experiment. (1mark)
2. Write an equation for the reaction that took place in the combustion tube. (1mark)
3. Why is it necessary to burn the gas coming out of tube K? (1mark)
The equation below represents changes in the physical state of ions metal:
Fe_(s) → Fe_(I) ΔH = + 15.4Kjmol^-1
Fe₍₁₎ → Fe_(g) ΔH = + 354Kjmol^-1Calculate the amount of heat energy required to change 10kg of solid iron to gaseous iron. (Fe = 56) (3marks)
The section below represents part of the periodic table. Study it and answer the questions that follow; the letters are not the actual symbol of the elements.
1. Explain why the atomic radius of T is smaller than that of M (1mark)
2. Compare the electrical conductivity of element X and B. (2marks)
Read the following passage and answer the questions.
A salt X was heated with slaked lime (calcium hydroxide). A colorless gas R with a characteristic smell that turns red litmus paper blue was evolved. A large quantity of this gas was passed through an inverted filter funnel into Copper (II) sulphate solution, and a deep blue solution M was obtained.
1. Identify gas R (1mark)
2. What is X most likely to be? (1mark)
3. Write an equation for the reaction between X and slaked lime. (1mark)
Consider the following reaction:

Sketch an energy level diagram showing the relative activation energies for the catalyzed and uncatalyzed reactions using the axes below. (2marks)
The diagram below shows the radiations emitted by a radioactive sample.
1. Identify radiation particles S and R (2marks)
1. Starting with red roses, describe how a solution containing the red pigments may be prepared? (2marks)
2. How can the solution be used as an indicator? (1mark)
1. Give one reason why some of the laboratory apparatus are made of ceramics. (1mark)
2. Name the two apparatus that can be used to measure approximately 75cm3 of dilute sulphuric (VI acid. (2marks)
Dry chlorine was collected using the set-up below.
1. Name a suitable drying agent for chlorine gas? (1mark)
2. State one property of chlorine gas which facilitates this method of collection. (1mark)
3. State one observation made on the moist blue litmus paper. (1mark)

MARKING SCHEME

What is the difference between chromatography and chromatology? (1mark)
- Chromatography is the method of separating coloured substance while chromatology is the study of colours.
When dilute Sulphuric (VI) acd is connected in a circuit to test conduction of electricity, the bulb lights while when concentrated Sulphuric (VI) acid is used in the same set-up, the bulb does not light. Explain this observation. (2marks)
- Coonc. Sulphuric (vi)acid is molecular hence ions are fixed while Dil. H₂SO₄ dissociatesin water providing H⁺ and SO₄^2-that conducts electricity.
Explain why Aluminium Chloride has PH 3 when dissolved in water? (2marks)
- AlCl₃ hydrolysis in water to form Al₂Cl₆ which is acidic.
Below is a list of substances.
Soap solution, common salt, urine, lemon juice and baking powder.
Select:
1. A substance that is likely to give a PH of 3.0 when tested? (1mark)
  - Lemon juice
2. A substance (s) which is likely to resemble sodium hydrogen carbonate.(1mark)
  - Baking powder.
3. Two substances when reacted are likely to give the product with same PH with common salt. (1mark)
  - Baking powder and lemon juice
    (accept – Soap solution and lemon)
Briefly explain the observation made when a small piece of sodium metal is dropped into a bowl of water. (3marks)
- It floats and darts on surface of water
- T moves and melts a silvery ball.
- It produces a hissing sound
1. Define Le Chatelier’s principle. (1mark)
  - When a change in condition is applied to a system in equilibrium, the system moves so as to oppose that change.
2. A fixed mass of a gas has a volume of 400cm² at 20°C, what temperature rise would produce a 10% increase in volume if the pressure remains constant. (3marks)
  V₁ = V₂
  T₁ T₂ Conversion of volume by 10% = 1
  400 = 440
  293 T₂ T2 = 440 x 293 = 3223/49.3°C
  400
Using Dots (.) and (x) diagram, show the number of electrons used in bonding of H₃O⁺ (2marks)
Explain why a luminous flame appears yellow. (2marks)
- Because of unburnt carbon particle which glows yellow when burnt.
Some sodium chloride was found to be contaminated with copper (II) oxide. Describe how a sample of sodium chloride can be separated from the mixture. (2marks)
- Add water to the mixture to dissolve Nacl.
- Filter to obtain Nacl as filtrate and CuO as residue.
- Evaporate the filtrate in evaporating dish over a water bath to obtain dry sample.
Hot platinum wire was lowered into a flask containing concentrated ammonia solutions shown below.

State and explain observations made (3marks)
- Hot platinum wire continues to glow red.
- Brown fumes are observed
- Hot platinum glows red since reaction of oxygen and NH3is exothermic.
- Brown fumes since NH₃ is oxidized in presence of Pt catalyst to produce NO which is further oxidized to NO₂
Give three characteristics of gases according to Kinetic theory of matter. (3marks)
- Continuous random motion
- Widely spread in space.
- Weak forces of attraction between molecules.
The formula below represents active ingredients of two cleansing agents A and B

Which one of the cleansing agents would be suitable to be used in water containing magnesium hydrogen carbonate? Explain. (2marks)
- Agent A
The set-up below was used to obtain a sample of iron

Write two equations for the reactions which occur in the combustion tube. (2marks)
- 2C + O₂ → CO₂
- 2CO + Fe₂ O₃ → 2 Fe + CO₂
The diagram below represents a set-up that can be used for the electrolysis of dilute Sulphuric acid.
1. Name the electrodes A and B (1mark)
  - A – Anode.
  - B – Cathode
2. Write an equation for the reaction taking place at electrode B. (1mark)
  - 4H⁺_(aq) + 4e_(aq) → 2H_2(g) / 2H⁺_(aq) + 2e → H2_(g)
3. What happens to the concentration of dilute sulphuric acid as the reaction continues? (1mark)
  - The concentration increases.
Describe one physical and one chemical test that can be used to identify ethane gas. (2marks)
- Physical - Burns with a yellow sooty flame.
- Chemical - Decolorizes purple acidified KMnO₄/
  - Decolorizes yellow bromine water
15cm³ of a solution containing 2.88g/dm³ of an alkali XOH completely reacts with 20cm³ of 0.045M sulphuric acid. Calculate the reactive atomic mass of X present in the alkali. (3marks)
2XOH + H₂SO₄ → X₂?SO₄ + H₂O
15 20
Moles of H2SO4 = 20 x 0.045 = 0.0009 moles
1000
Mols of XOH = 0.0009 x 2 = 0.0018
Molarity of XOH = M x 1000 = (0.0018 x 1000)
V 15
= 0.12M
RFM = Concing/dmo
Conc in m
= 2.88
0.12
= 24
X + 16 + 1 = 24
X = 7
Using equations state and explain the changes in mass that occur when the following are heated separately in open crucible. (3marks)
1. Magnesium metal
  - In magnesium the mass increases
  - @Mg(s) + O2(g) 2MgO(g)/ 3Mg(s) + N2 Mg3N2(s)
2. Zinc carbonate
  - Zinc carbonate mass decreases.
    ΔH
  - ZnCO_3(s) → ZnO_(s) + CO_2(g)
In the space provided below, draw a set-up that can be used to show the reaction between nitrogen (I) oxide with copper to give Nitrogen gas. (3marks)
The flow chart below shows some process in extraction of lead metal. Study it and answer the questions that follow;
1. Name two raw materials that were fed into Unit I (1mark)
  - Lead Sulphide
  - Air/Oxygen
2. State one environment hazard associated with the process in Unit I. (1mark)
  - SO₂ leads to formation of acidic rain
  - SO₂ Causes respiratory infection
3. What is the function of Coke in Unit II (1mark)
  - Reduces lead (II) oxide into lead metal
Sulphur exhibits as an allotropy.
1. What is allotropy? (1mark)
  - Existence of element in more than one structural form in the same physical state.
2. Name the two allotropes of sulphur. (1mark)
  - Rhombic
  - Monoclinic
3. Sulphur powder was placed in a deflagrating spoon and heated on a Bunsen burner.
  1. State the observation made. (1mark)
    - Blue flame/pungent smell
  2. The product obtained was dissolved in water. Comment on the PH of the solution formed. (1mark)
    - Acidic/low PH
The set-up below was used to prepare a sample of an organic compound X.
1. Identify gas X (1mark)
  - Propane
2. Write the equation for the reaction that produces gas X. (1mark)
  - CH₃Ch₂CH₂COONa + NaOH → Na₂CO₃ + C₃H₈ (ignore state symbols)
3. 1 Mole of chlorine was reacted with gas X in presence of sunlight.
  1. State one observation made. (½ mark)
    - Green – Yellow chlorine turns Yellow
  2. Name the major product formed. (½ mark)
    - Chloropropane
The apparatus shown below was used to investigate the effect of carbon (II) oxide on Copper (I) oxide.
1. State the observation that was made in the combustion tube at the end of the experiment. (1mark)
  - Black solid turns brown
2. Write an equation for the reaction that took place in the combustion tube. (1mark)
  - CO_(g) + CuO_(s) → Cu_(g) + CO_2(g)
3. Why is it necessary to burn the gas coming out of tube K? (1mark)
  - To avoid pollution when exposed to air.
The equation below represents changes in the physical state of ions metal:

Calculate the amount of heat energy required to change 10kg of solid iron to gaseous iron. Fe = 56 (3marks)
I mole of Fe(56) required 154 + 354 = 396.5KJ/
10,000g =?
10,000 x 360.4 = 65964.285KJ.
56
The section below represents part of the periodic table. Study it and answer the questions that follow; the letters are not the actual symbol of the elements.
1. Explain why the atomic radius of T is smaller than that of M (1mark)
  - T has more protons hence the nuclear charge than M attracting outermost electrons closer to the nucleus reducing atomic radius.
2. Compare the electrical conductivity of element X and B. (2marks)
  - B has higher conductivity than X since B has three/more delocalized electrons than X which has one/less.
Read the following passage and answer the questions.
A salt X was heated with slaked lime (calcium hydroxide). A colorless gas R with a characteristic smell that turns red litmus paper blue was evolved. A large quantity of this gas was passed through an inverted filter funnel into Copper (II) sulphate solution, and a deep blue solution M was obtained.
1. Identify gas R (1mark)
  - Ammonia gas
2. What is X most likely to be? (1mark)
  - Ammonium chloride.
3. Write an equation for the reaction between X and slaked lime. (1mark)
  - Ca(OH)_2(aq) + NH₄Cl_(aq) CaCl_2(aq) + 2NH_3(g) + H₂O_(I)
Consider the following reaction:

Sketch an energy level diagram showing the relative activation energies for the catalyzed and unanalyzed reactions using the axes below. (2marks)
The diagram below shows the radiations emitted by a radioactive sample.

Identify radiation particles S and R (2marks)
- S Alpha accept symbols
- R Beta
1. Starting with red roses, describe how a solution containing the red pigments may be prepared? (2marks)
  - Crush roses using mortar and pestle to obtain smooth paste
  - Add propanone /ethanol and continue crushing to dissolve red pigment
  - Filter to obtain red pigment solution
  - Place under the sun for propanone to evaporate.
2. How can the solution be used as an indicator. (1mark)
  - Add drops of pigments in different sample of acid and bases ½ hence show some colour in acid but different colour in acid ½
1. Give one reason why some of the laboratory apparatus are made of ceramics. (1mark)
  - They do not react with acids and bases.
2. Name the two apparatus that can be used to measure approximately 75cm3 of dilute sulphuric (VI acid. (2marks)
  - Pipette
  - Burette
  - Measuring cylinder
Dry chlorine was collected using the set-up below.
1. Name a suitable drying agent for chlorine gas? (1mark)
  - Conc. Sulphuric (iv) acid/anhydrous calcium chloride.
2. State one property of chlorine gas which facilitates this method of collection. (1mark)
  - Slightly denser than air.
3. State one observation made on the moist blue litmus paper. (1mark)
  - It turns red then decolourises