Rehan takes two test tubes. In the first test tube, he takes lead nitrate solution and in the second, he takes a few zinc granules. He adds potassium iodide solution to lead nitrate solution in the first test tube. He adds dilute sulphuric acid in the second test tube containing zinc granules.
(A) What is observed in the first test tube on adding potassium iodide solution?
| Formula of Precipitate Formed | Colour of Precipitate | |
|---|---|---|
| (a) | KNO₃ | Yellow |
| (b) | KNO₃ | Brown |
| (c) | PbI₂ | Yellow |
| (d) | PbI₂ | Brown |
(B) When dilute sulphuric acid is added to a few zinc granules in the second test tube:
(I) bubbles of hydrogen gas can be seen.
(II) bubbles of carbon dioxide can be seen around zinc granules.
(III) the flask becomes hot.
(IV) colour of solution changes to blue.
Select the correct observations:
(a) Only (I)
(b) Both (I) and (III)
(c) Both (II) and (III) (d) (I), (III) and (IV)
(C) Assertion (A): A single displacement reaction takes place when zinc granules are added to dilute sulphuric acid.
Reason (R): Hydrogen gas is evolved in the reaction and there is no change in colour.
(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true, and (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.
(D) Suppose Rehan added dil. hydrochloric acid in place of sulphuric acid in the second test tube. Select the correct observation made by him.
(a) Chlorine gas will be evolved.
(b) The test tube will become cold as heat is absorbed during this reaction.
(c) Hydrogen gas will be evolved.
(d) A precipitate of zinc chloride will be formed.
OR
(D) The reaction between lead nitrate and potassium iodide is a double displacement reaction. If a student heats only lead nitrate powder and gets the brown coloured gas. What type of reaction is heating of lead nitrate? Identify the brown coloured gas.
| Type of reaction | Name of gas | |
|---|---|---|
| (a) | Decomposition | NO₂ |
| (b) | Combination | NO₂ |
| (c) | Decomposition | O₂ |
| (d) | Combination | O₂ |
(A) What is observed in the first test tube on adding potassium iodide solution?
| Formula of Precipitate Formed | Colour of Precipitate | |
|---|---|---|
| (a) | KNO₃ | Yellow |
| (b) | KNO₃ | Brown |
| (c) | PbI₂ | Yellow |
| (d) | PbI₂ | Brown |
(I) bubbles of hydrogen gas can be seen.
Explanation: In the second test tube, a single displacement reaction takes place,
In this reaction, hydrogen gas is evolved and no colour change takes place.
(D) (c) Hydrogen gas will be evolved.
Explanation: If we add dilute hydrochloric acid instead of dilute sulphuric acid to the second test tube containing zinc granules, the following reaction will take place:
Bubbles will be observed as hydrogen gas will be evolved. It is also an exothermic reaction as heat is evolved during this reaction. However, as zinc chloride formed is soluble in the solution, no precipitate will be formed.
(D) (a) Type of reaction: Decomposition; Name of gas:
Explanation: If a student heats only lead nitrate powder, the reaction taking place will be thermal decomposition.
Lead nitrate would decompose into yellow coloured lead oxide, brown coloured nitrogen dioxide gas and colourless oxygen gas.