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Standard VIII
Chemistry
Question

Four students A, B, C, and D noted the initial colour of the solution in beakers I, II, III and IV. After inserting zinc rods in each solution and leaving it undisturbed for two hours, noted the colour of each solution again.
The recorded observations in the form of the table given below:
Which student noted the colour change in all the four beakers correctly.
210851_2cc0d8486b074baea6fb31dea51237d9.png
  1. (B)
  2. (C)
  3. (D)
  4. (A)

A
(A)
B
(C)
C
(D)
D
(B)
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Solution
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The student designated as (A) made the correct observation.
  • In breaker (I), the solution remained colourless or unchanged in colour since no chemical reaction was possible. Actually, aluminium is placed above zinc in the activity series.

  • In beaker (II), no chemical reaction was possible and the solution remained colourless.

  • In beaker (III), the initial colour of the ferrous sulphate solution was light green. It became colourless after the reaction.
Zn(s)+FeSO4(aq)→ZnSO4(aq)+Fe(s)
Blue Colourless

  • In beaker (IV), the initial colour of the ferrous sulphate solution was blue. It became colourless after the reaction.
Zn(s)+CuSO4(aq)→ZnSO4(aq)+Cu(s)
Blue Colourless

Option A is correct.

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Similar Questions
Q1
Four students A, B, C, and D noted the initial colour of the solution in beakers I, II, III and IV. After inserting zinc rods in each solution and leaving it undisturbed for two hours, noted the colour of each solution again.
The recorded observations in the form of the table given below:
Which student noted the colour change in all the four beakers correctly.
210851_2cc0d8486b074baea6fb31dea51237d9.png
View Solution
Q2
Four students A, B, C and D noted the initial colour of the solutions in beakers I, II, III and IV. After inserting zinc rods in each solution and leaving it undisturbed for two hours, noted the colour of each solution again.



They recorded their observations in the form of a table given below:
Student Colour of the solution I II III IV
A Initial
Final		 Colourless
Colourless		 Colourless
Colourless		 Light green
Colourless		 Blue
Colourless
B Initial
Final		 Colourless
Colourless		 Light yellow
Colourless		 Light green
Light green		 Blue
Colourless
C Initial
Final		 Colourless
Light blue		 Colourless
Colourless		 Light green
Colourless		 Blue
Light blue
D Initial
Final		 Light green
Colourless		 Colourless
Colourless		 Light green
Dark green		 Blue
Colourless

Which student noted the colour change in all the four beakers correctly?
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Q3

A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below

(I) Sodium hydroxide is in the form of pellets.

(II) It dissolves in water readily.

(III) The beaker appears cold when touched from outside.

(iv) The red litmus paper turns blue when dipped into the solution


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Q4
Aluminium sulphate and copper sulphate solutions were taken in two test tubes I and II respectively. Iron filings were then added to both the solutions. The four students A, B, C and D recorded their observations in the form of a table as given below.
Student Aluminium sulphate solution (I) Copper sulphate solution (II)
A Colourless changes to light green Blue colour of the solution is retained
B Colour of colourless solution does not change Blue colour of the solution changes to light green
C Colourless solution changes to light blue Blue colour of the solution changes to colourless
D
 Colour of colourless solution remains unchanged Blue colour of the solution fades away
The correct set of observations have been recorded by the students :
(1) A
(2) B
(3) C
(4) D
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Q5
Green coloured ferrous sulphate solution is taken in four beakers, A, B, C and D. Strips of magnesium, zinc, copper and silver are dipped in A, B, C and D respectively. Green colour fades away slowly in two beaker. Identify the beakers.
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