Chemistry Trial Exams Paper 3 Questions - Alliance Boys High School Mock December 2020

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Instructions to Candidates

  1. Write your name and index number in the spaces provided above. 
  2. Sign and write the date of examination in the spaces provided above
  3. Answer ALL the questions in the spaces provided in the question paper
  4. KNEC Mathematical tables and electronic calculators may be used for calculations
  5. All working MUST be clearly shown where necessary
  6. This paper consists of 6 printed pages
  7. Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing 
  8. Candidates should answer the questions in English

FOR EXAMINERS USE ONLY

Question  Maximum score  Candidates score 
 1  19  
 2  11  
 3  10  
Total  40  


QUESTIONS

Question One
You are provided with:

  • Solid A, metal carbonate M2CO3
  • Solution B, hydrochloric acid for use in questions 1 and 2
  • Solution C 0.30M sodium hydroxide
  • Methyl orange indicator

You are required to:

  • for Prepare a dilute solution of hydrochloric acid and determine its concentration;
  • Determine the solubility of solid A in water

Procedure:
Reserve one dry conical flask for use in step 4)

  1. Step 1 Place all of solid A in a 250 ml dry beaker. Add 100cm of distilled water to solid A in the beaker. Using glass rod, stir the mixture thoroughly for about two minutes. Leave the mixture to stand and proceed with step 2 and 3.
  2. Step 2 using a pipette and pipette fller, place 25.0cm of solution B in a 250mlvolumetric flask. Add about 200cm3 of distilled water. Shake the mixture well and add distilled water to make up to the mark. Label this as solution D
  3. Step 3 Fill a burette with solution C. Using a pipette and a pipette filler place 25cm of solution D into a 250ml conical flask. Add two drops of the indicator provided and titrate solution with C. Record your results in table 1. Repeat the titration two more times and complete table 1. Retain the remaining solution D for use in step 5 
  4. Step 4: filter the mixture obtained in step 1 using a dry filter funnel into a dry conical flask. Label the filtrate as solution A. 
  5. Step 5. Clean the burette and fill it with solution D. Using a pipette and pipette filler, place 25cms of solution A into a 250ml conical flask. Add two drops of the indicator provided and titrate solution A with solution D. Record your results in table 2. Repeat the titration two more times and complete table 2.

Table 1

  II III 
Finial burette reading (cm3)      
Initial burette reading (cm3)      
Volume of solution C used (cm3)       
  1. Calculate
    1. The average volume of solution C used. (1mk)
    2. Moles of sodium hydroxide in the average volume of solution C used.(1mk)
    3. Calculate moles of HCl in 25.0cm of solution
    4. Calculate the Molarity of HCl solution D

Table II

  II III 
Finial burette reading (cm3)      
Initial burette reading (cm3)      
Volume of solution C used (cm3)       

(4 marks)

b). Calculate;

  1. Average volume of solution D used
  2. Moles of HCl in average volume of solution D used
  3. Moles of metal carbonate in solid A in 25.0cm3 of solution A (2 marks)
  4. The solubility of metal carbonate solid A in water (relative molecular mass of metal carbonate = 74) assume density of solution is 1g/cm3 (2 marks)

2. You are provided with solids E and solid F. carry out the test below, write your observation and you are provided with solid A, carry out the test below and answer the questions that follow.

  1. Describe the appearance of solid E (1mk)
    1. Place half of solid in a boiling tube and heat strongly. Test the gas produced with a burning splint
      Observations (1mk)
      Inferences (1mk)
    2. Add dilute hydrochloric to the residue and shake, divide the resulting solution into three portions 
      Observations (1mk)
      Inferences (2mk)
    3. To the first portion add aqueous ammonia drop wise till in excess 
      Observations (1mk)
      Inferences
    4. To the second portion add solid a 
      Observations (1mk)
      Inferences (1mk)
  2. Identify the cation and anion present in E
    Cation:
    Anion:

3. You are provided with solid G
Carry out the tests below write your observations and inferences in the spaces provided

  1. Place the remaining portion of solid G in a boiling tube and add 10cm of distilled water divide the resulting solution into five portions
    1. To the first portion add 2-3 drops of acidified potassium dichromate (VI) solution and warm
      Observations (1mk)
      Inferences (1mk)
    2. To the second portion add 2-3 drops of acidified potassium manganate (VII) solution and warm
      Observations (1mk)
      Inferences (1mk)
    3. To the third portion warm and then add NaHCO
      Observations (1mk)
      Inferences (1mk)
    4. To the four portion add bromine water 
      Observations (1mk)
      Inferences (1mk)
    5. Determine the pH using universal Indicator paper 
      Observations (1mk)
      Inferences (1mk)

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