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.
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They recorded their observations in the form of a table given below:
Student
| Colour of the solution
| I | II | III | IV |
A | InitialFinal | ColourlessColourless | ColourlessColourless | Light greenColourless | BlueColourless |
B | InitialFinal | ColourlessColourless | Light yellowColourless | Light greenLight green | BlueColourless |
C | InitialFinal | ColourlessLight blue
| ColourlessColourless | Light greenColourless | BlueLight blue |
D | InitialFinal | Light greenColourless | ColourlessColourless | Light greenDark green | BlueColourless |
Which student noted the colour change in all the four beakers correctly?"
Correct answer: The observation made by student A is correct.
Explanation:
- For beaker I, the zinc rod is dipped in aluminium sulphate, as zinc is less reactive than aluminium so, no reaction will take place.
- For beaker II, the zinc rod is dipped in zinc sulphate, no reaction takes place as the zinc rod is dipped in zinc solution.
- For beaker III, zinc rod is dipped in ferrous sulphate, as zinc is more reactive than ferrous sulphate (light green), it reacts with zinc to produce zinc sulphate (colourless).
- For beaker IV, the zinc rod is dipped in copper sulphate (light blue), as zinc is more reactive than copper sulphate it reacts with zinc to produce zinc sulphate (colourless).
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