Acids, Bases and Indicators Questions and Answers - Chemistry Form 1 Topical Revision

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Questions

  1. The table below shows solutions A, B and C are tested and observations records as shown:
    Solution  Observations on indicator
    A Methyl orange turns yellow
    B Phenolphthalein turns colourless
    C Litmus turns purple
    1. Using the table above, name an acid
    2. How does the pH value of 1M potassium hydroxide solution compare with that of 1M aqueous ammonia? Explain
  2. The information below gives PH values of solutions V, W, X, Y, Z
    Solution  PH values
    V
    W
    X
    Y
    Z
    2
    6.5
    11
    14
    4.5
    1. Which solution is likely to be:
      1. Calcium hydroxide? 
      2. Rain water?
    2. Which solution would react most vigorously with Zinc carbonate
  3.  
    1. Complete the table below to show the colour of the given indicator in acidic and basic solutions.
      Indicator Colour in
      Methyl Orange Acidic Solution Basic Solution
         
      Phenolphthalein  Colourless  
    2. How does the PH value of 0.1M potassium hydroxide solution compare with that of 0.1M aqueous ammonia? Explain.
  4. Use the information given below to answer the questions that follow:
    Solution  G H I J K
    pH 1.5  6.5  13.0  7.0  8.0
    1. Which of the solutions would be used to relieve a stomach upset caused by indigestion?
    2. Which solution is likely to be:
      1. Dilute sulphuric acid?
      2. Sodium hydroxide solution?
  5. Solid copper (II) oxide is a base although it does not turn litmus paper to blue. Explain
  6. Below are the pH values of 4 types of medicine represented by letters P, Q, R and S
    MEDICINE pH VALUES
    P
    Q
    R
    S
    7.0
    5.0
    8.0
    6.0

    1. It is not advisable to use S when a patient has indigestion .Explain
    2. What is the role of chemistry in drug manufacture
  7. Explain why very little Carbon (IV) oxide gas is evolved when dilute sulphuric (VI) acid is added to lead (II) carbonate
  8. State one commercial use of Calcium Oxide
  9. The following data gives the pH values of some solutions
    Solution  pH
    P
    Q
    R
    14.0
    6.8
    2.5
    1. What colour change would occur in solution P on addition of two drops of phenolphthalein indicator?
    2. State the pH value of a resulting solution when equal moles of solution P and R react
  10. In an experiment, ammonia gas was prepared by heating ammonium salt with an alkali.
    After drying, ammonia gas was collected at room temperature and pressure.
    1. What is meant by the term alkali?
    2. Explain using physical properties of the gas why ammonia is not collected by downward delivery
  11. The table shows the colours obtained when some indicators are added to solutions:-
    Solution Blue litmus paper  Indicator W
    Distilled water ………………….. Colourless
    Calcium hydroxide  Blue Pink
    Nitric acid ………………………… Colourless
    1. Complete the table by filling in the missing colours
    2. Identify indicator W
    1. Flower extracts can be used as Acid-base indicators. Give two limitations of such indicators
    2. The diagram below shows spots of pure substances W, X, and Y on a chromatography paper. Spot Z is that of a mixture
      chromatogram of pure substance
      After development W, X, and Y were found to have moved 9cm3, 4cm3 and 7cm3 respectively. Z has separated into two spots which have moved 7cm3 and 9cm3:-
      On the diagram:-
      1. Label the baseline and solvent front
      2. Show the position of all the spots after development
      3. Identify the substances present in mixture Z
  12. A beekeeper found that when stung by a bee, application of a little solution of sodium hydrogen carbonate helped to relieve the irritation of the affected area. Explain
  13. 10g of sodium hydrogen carbonate were dissolved in 20cm3 of water in a boiling tube. Lemon juice was then added dropwise with shaking until there was no further change.
    1. Explain the observation which was made in the boiling tube when the reaction was in progress
    2. What observations would be made if the lemon juice had been added to copper turnings in a boiling tube?
  14. Complete the table below to show the colour of the given indicator in acidic and basic solutions:
    Indicator Colour in acidic solution Basic Solution
    Methyl orange Pink  
    Phenolphthalein   Pink
  15. Solutions can be classified as acids, bases or neutral. The table below shows solutions and their pH values:-
     Solutions  pH Values
     K  1.5
     L  7.0
     M  14.0
    1. Select any pair that would react to form a solution of PH 7
    2. Identify two solutions that would react with aluminium hydroxide. Explain

Answers

  1.  
    1. B
    2. pH of potassium hydroxide is higher than that of aqueous ammonia. KOH ions are dissociated more than that of aqueous NH3
  2.  
    1.  
      1. X
      2. W
    2. V
  3.  
    1. Methyl Orange Red/Pink ✓½
      Phenolphthalein Colourless/Pink ✓½
    2. The PH of 0.1M KOH is higher than of 0.1M aqueous ammonia ✓1
      KOH is strongly dissociated in solution. ✓1
  4.  
    1. K
    2.  
      1. G
      2. I
  5. Copper (II) oxide is insoluble in water hence there are no OH- ions in the mixture
  6.  
    1. S is acidic and would make the situation worse ✓ ½
    2. Discovery of drugs processing and testing is the work of chemists. Chemists are professionals who have studied chemistry ✓ ½
  7. Its due to formation of insoluble Lead(II) carbonate hence preventing any further reaction.
  8. CaO is used in correcting soil acidity. √ 1
  9.  
    1. Pink
    2. 7.0
  10.  
    1. alkali is soluble base. √ 1
    2. Because it is lighter than air. √ 1
  11.  
    1.  
       Solution  Blue litmus paper  Indicator W
         Blue  
           
         Red  
    2. Phenolphthalein
  12.  
    1. -give inconsistent results√ ½
      -expire shortly√ ½
    2.  

      1. Base line and solvent front
      2. Maximum sports-award 1 ½ mks
        Fail any one- award
      3. W √ ½ and Y √ ½
  13. Sting of a bee is acidic √ 1 and is neutralized by sodium hydrogen carbonate√ ½ into a salt, carbon IV) oxide and water. This gives pain relief. √ ½
  14.  
    1. There was production of effervescence . The lemon juice contain an acid that reacts with the carbonate to produce carbon (IV) oxide.
    2. No production of bubbles. Copper is below hydrogen in the reactivity
  15.  
    1. Yellow
    2. Colourless
  16.  
    1. K and M
    2. K and M

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