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Chemistry Paper 2: Form 4 QA Model – Document ID 20250302001

Name: Chemistry Paper 2: Form 4 QA Model – Document ID 20250302001
Brand: 8-4-4 Exams and Tutorials
SKU: 1170
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Featured Questions

Here are the featured questions from the “KCSE MOCK-CHEMISTRY PAPER 2 QA MODEL”:

Question 1:
- (a) Write down the electron arrangement of the elements A and B from the given ion configurations A³⁺ and B²⁻.
- (b) Study the information in the table and answer the following:
  - (i) Which element is a gas at room temperature? Explain, taking room temperature as 25ºC.
  - (ii) Which element does not form an oxide? Explain.
  - (iii) Write down the equation for the reaction between elements K and M.
  - (iv) What type of bond would exist in the compound formed when elements M and L react? Give a reason for your answer.
  - (v) Select the most electropositive element. Explain.
  - (vi) Why is the boiling point of element L higher than that of element K?
Question 2:
- (a) The sketch below represents a graph obtained when zinc granules were reacted with excess 0.2M Sulphuric (VI) acid in the presence of a catalyst. Answer the following:
  - (i) Write an equation for the reaction that took place.
  - (ii) Explain why there is a loss in mass.
  - (iii) Name the catalyst used.
  - (iv) (a) Sketch, on the same axes, the curves obtained when:
    - I the same mass of zinc powder was used under the same conditions.
    - II no catalyst was used.
  - (b) In the contact process, explain:
    - (i) What is meant by dynamic equilibrium?
    - (ii) How a decrease in temperature affects the position of equilibrium.
    - (iii) How a decrease in pressure affects the position of equilibrium.
    - (iv) State and explain the observation made when aqueous sodium hydroxide is added to the mixture of chromate and dichromate ions.
Question 3:
- (a) The table below shows the standard reduction potentials for four half-cells. Answer the following:
  - (i) Identify the strongest reducing agent.
  - (ii) Write the equation for the reaction that takes place when solid G is added to a solution containing H₂⁺ ions.
  - (iii) Calculate the E° value for the reaction in (ii) above.
- (b) The diagram shows the apparatus used to electrolyze acidified water. Answer the following:
  - (i) Identify the electrode at which oxidation takes place.
  - (ii) Give a reason why it is necessary to acidify the water.
  - (iii) Explain why hydrochloric acid is not used to acidify the water.
- (c) During electrolysis of aqueous copper (II) sulfate, calculate the mass of copper metal obtained using 144750 C of electricity.
Question 4:
- (a) Describe how a sample of the solution could be tested to find out if it contained chloride ions.
- (b) Given a series of experiments with potassium chloride and varying volumes of water, answer the following:
  - I. Calculate the missing solubility values.
  - II. Plot the graph of solubility against temperature.
  - (i) What is the effect of temperature on the solubility of potassium chloride in water?
  - (ii) From the graph, what is the solubility of potassium chloride at 60ºC?
  - (iii) At what temperature will solubility be 35g/100g of water?
  - (iv) What is the mass of crystals deposited when the solution is cooled from 70ºC to 40ºC?
Question 5:
- (a) Below is a simplified diagram of the Downs cell used for the manufacture of sodium. Answer the following:
  - (i) What material is the anode made of? Give a reason.
  - (ii) What precautions are taken to prevent chlorine and sodium from recombining?
  - (iii) Write an ionic equation for the reaction in which chlorine gas is formed.
- (b) In the Downs process, identify the salt added to lower the melting point of sodium chloride and explain why it is necessary to lower the temperature.
- (c) Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of sodium in the Downs process.
- (d) Give the formulae of the oxides formed when sodium metal reacts with air.
- (e) Draw a well-labeled diagram that can be used to extract zinc metal by electrolysis.
Question 6:
- (a) For the compounds given, answer the following:
  - (i) Give the systematic name of each compound.
  - (ii) Write the molecular formula of each compound.
  - (iii) How does the boiling point of I compare to that of II? Explain.
  - (iv) Name gas J that is bubbled into concentrated Sulphuric (VI) acid to yield compound II.
  - (v) Draw the structural formula of the compound immediately after compound I in the homologous series.
- (b) For the two monomers given, answer the following:
  - (i) Name the type of polymerization these monomers would undergo.
  - (ii) Draw the structural formula to represent the polymer formed.
  - (iii) What is the name of the polymer?
  - (iv) State the use of this polymer.
- (c) Select a detergent suitable for washing in water containing magnesium chloride and explain.
Question 7:
- (a) Define the term molar heat of neutralization.
- (b) Write an ionic equation for the neutralization reaction between hydrochloric acid and sodium hydroxide.
- (c) Calculate:
  - (i) The amount of heat produced during the reaction.
  - (ii) The molar heat of neutralization of sodium hydroxide.
  - (iii) Explain why the molar heat of neutralization of 1M NaOH is higher than that of 1M NH₄OH when reacted with 1M HCl.
- (d) Write the thermochemical equation for the reaction.
- (e) Draw an energy level diagram for the reaction.
- (f) Calculate the heat of formation of ethanol based on the heats of combustion provided.

These questions cover a wide range of chemistry topics, including atomic structure, chemical reactions, electrochemistry, solubility, organic chemistry, and thermodynamics.

Categories: Chemistry Exams and Notes, Form 4 Examinations Tags: #CHEMISTRY, #exams, #KCSE Brand: 8-4-4 Exams and Tutorials

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Description

The document is a chemistry examination paper for the Kenya Certificate of Secondary Education (KCSE), specifically Paper 2, which focuses on theoretical concepts in chemistry. It consists of various sections, including instructions for candidates, several questions, and a marking scheme. Below is a comprehensive overview of the key sections and topics covered:

General Structure

Title and Instructions: The paper is titled “CHEMISTRY PAPER 2 (THEORY)” and instructs candidates on how to fill in their details (name, index number, etc.) and answer the questions.
Scoring: The paper includes a section for expected scores and candidate scores for each question, totaling a maximum of 80 marks.

Question Breakdown

Electron Arrangement and Element Properties:
- Candidates are asked to deduce electron arrangements for elements based on given ion configurations.
- Questions explore properties of elements, such as states at room temperature, oxide formation, and types of chemical bonds.
Chemical Reactions:
- A section asks candidates to write chemical equations for reactions, analyze mass changes during reactions, and identify catalysts.
- Questions about equilibrium in reactions and how changes in temperature and pressure affect equilibrium positions are included.
Electrochemistry:
- Candidates must interpret standard reduction potentials, identify reducing agents, and write ionic equations for reactions involving electrolysis.
- Questions on the electrolysis of water and copper(II) sulfate are included, along with calculations related to electricity and mass of metals obtained.
Solubility and Temperature:
- A section involves experiments to determine the solubility of potassium chloride (KCl) at different temperatures, requiring candidates to analyze data, draw graphs, and deduce solubility trends.
Electrolytic Processes:
- Candidates answer questions related to the Downs cell and the production of sodium, including the materials used for electrodes, precautions to prevent recombination of products, and the role of added salts to lower melting points.
Organic Chemistry:
- Questions involve identifying compounds based on structural formulas, naming them systematically, and discussing their boiling points and reactions.
- The document covers polymerization and the properties of different types of detergents.
Heat of Reaction:
- Candidates are asked to define molar heat of neutralization, write thermochemical equations, and draw energy level diagrams.
Calculations:
- Many questions require calculations involving chemical quantities, such as determining the mass of products formed from given reactants and analyzing thermodynamic properties.

Marking Scheme

The document includes a marking scheme that provides answers and grading criteria for each question, detailing what constitutes correct and complete responses.

Conclusion

Overall, the document is a comprehensive assessment tool for chemistry students, designed to evaluate their understanding of theoretical concepts, practical applications, and problem-solving abilities in chemistry. It covers a wide range of topics, including inorganic chemistry, electrochemistry, organic chemistry, and thermodynamics, ensuring a thorough examination of the candidates’ knowledge and skills.