JAMB and WAEC Chemistry questions

800 questions with answers and explanations. Tap an option to check yourself.

1. Question 781· Water· JAMB

   Hard water forms scum with soap because

   • Ait contains dissolved oxygen
   • Bit contains sodium ions
   • Cit is too acidic
   • Dcalcium and magnesium ions react with the soap

   Show answer

   Answer: D. calcium and magnesium ions react with the soap

   Explanation and discussion

2. Question 782· Water· WAEC

   A test for pure water is that it

   • Aturns lime water milky
   • Bboils at 100 °C at standard pressure
   • Cturns red litmus blue
   • Dhas a pH of 2

   Show answer

   Answer: B. boils at 100 °C at standard pressure

   Explanation and discussion

3. Question 783· Water· JAMB

   Soap forms scum in hard water because of dissolved

   • Acalcium and magnesium ions
   • Bsodium ions
   • Cchloride ions
   • Dhydrogen ions

   Show answer

   Answer: A. calcium and magnesium ions

   Explanation and discussion

4. Question 784· Water· WAEC

   Anhydrous copper(II) sulphate is used to test for water because it turns from

   • Ablue to white
   • Bcolourless to pink
   • Cgreen to red
   • Dwhite to blue

   Show answer

   Answer: D. white to blue

   Explanation and discussion

5. Question 785· Water· WAEC

   In water treatment, alum is added to

   • Aadd flavour
   • Bkill bacteria
   • Csoften water
   • Dcoagulate fine suspended particles

   Show answer

   Answer: D. coagulate fine suspended particles

   Explanation and discussion

6. Question 786· Water· JAMB

   Permanent hardness of water can be removed by

   • Aboiling
   • Badding washing soda
   • Cfiltration
   • Dadding chlorine

   Show answer

   Answer: B. adding washing soda

   Explanation and discussion

7. Question 787· Water· JAMB

   Water is called a universal solvent because it

   • Ais cheap
   • Bdissolves every substance
   • Cdissolves a wide range of substances
   • Dboils at 100 °C

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   Answer: C. dissolves a wide range of substances

   Explanation and discussion

8. Question 788· Water· JAMB

   Sodium reacts with cold water to produce

   • Asodium oxide and oxygen
   • Bsodium hydroxide and hydrogen
   • Csodium chloride and water
   • Dsodium and steam

   Show answer

   Answer: B. sodium hydroxide and hydrogen

   Explanation and discussion

9. Question 789· Water· WAEC

   Temporary hardness in water is caused by dissolved

   • Acalcium hydrogentrioxocarbonate(IV)
   • Bcalcium tetraoxosulphate(VI)
   • Csodium chloride
   • Dmagnesium chloride

   Show answer

   Answer: A. calcium hydrogentrioxocarbonate(IV)

   Explanation and discussion

10. Question 790· Water· WAEC

    Boiling removes temporary hardness because calcium hydrogencarbonate

    • Aturns to calcium chloride
    • Bevaporates
    • Cdecomposes to insoluble calcium carbonate
    • Ddissolves further

    Show answer

    Answer: C. decomposes to insoluble calcium carbonate

    Explanation and discussion

11. Question 791· Water· WAEC

    Temporary hardness of water can be removed by

    • Aadding chlorine
    • Bfiltration
    • Cboiling
    • Daeration

    Show answer

    Answer: C. boiling

    Explanation and discussion

12. Question 792· Water· WAEC

    In water treatment, the water is passed through sand beds in order to

    • Asoften it
    • Bkill bacteria
    • Cadd fluoride
    • Dfilter out suspended particles

    Show answer

    Answer: D. filter out suspended particles

    Explanation and discussion

13. Question 793· Water· WAEC

    The test for water is that it turns anhydrous copper(II) sulphate

    • Afrom blue to red
    • Bfrom blue to white
    • Cfrom white to green
    • Dfrom white to blue

    Show answer

    Answer: D. from white to blue

    Explanation and discussion

14. Question 794· Water· WAEC

    Rain water is the purest natural water, but it may contain dissolved

    • Acalcium salts
    • Bsodium chloride
    • Cgases from the air
    • Dsand

    Show answer

    Answer: C. gases from the air

    Explanation and discussion

15. Question 795· Water· WAEC

    Which of the following methods removes temporary hardness of water but not permanent hardness?

    • AAdding washing soda
    • BBoiling
    • CIon exchange
    • DDistillation

    Show answer

    Answer: B. Boiling

    Explanation and discussion

16. Question 796· Water· JAMB

    When calcium hydrogentrioxocarbonate(IV) solution is boiled, it forms

    • Acalcium chloride
    • Bcalcium oxide and hydrogen
    • Ccalcium hydroxide only
    • Dcalcium trioxocarbonate(IV), water and carbon(IV) oxide

    Show answer

    Answer: D. calcium trioxocarbonate(IV), water and carbon(IV) oxide

    Explanation and discussion

17. Question 797· Water· JAMB

    Anhydrous copper(II) tetraoxosulphate(VI) is used to test for water because it

    • Aturns from white to blue
    • Bturns from blue to white
    • Cgives off a gas
    • Dturns black

    Show answer

    Answer: A. turns from white to blue

    Explanation and discussion

18. Question 798· Water· WAEC

    Permanent hardness can be removed by adding

    • Aalum only
    • Bboiling only
    • Cchlorine
    • Dwashing soda (sodium carbonate)

    Show answer

    Answer: D. washing soda (sodium carbonate)

    Explanation and discussion

19. Question 799· Water· WAEC

    Caustic soda pellets left open in the laboratory become wet and finally form a solution. They are

    • Avolatile
    • Befflorescent
    • Chygroscopic only
    • Ddeliquescent

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    Answer: D. deliquescent

    Explanation and discussion

20. Question 800· Water· WAEC

    White anhydrous copper(II) tetraoxosulphate(VI) turns blue when it

    • Adissolves in acid
    • Bis heated
    • Cabsorbs water
    • Dreacts with oxygen

    Show answer

    Answer: C. absorbs water

    Explanation and discussion