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

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
12. 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
       
       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
13. 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
14. 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?
15. 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

16. 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. 
          
       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