i. What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube? ii. What type of reaction is this? iii. Write a balanced chemical equation to represent the above reaction. OR A brown substance ‘X’ on heating in air forms a substance ‘Y’. When hydrogen gas is passed over heated ‘Y’, it again changes back into ‘X’. i. Name the substance ‘X’ and ‘Y’ ii. Name the type of chemical reactions occurring during both the changes. iii. Write the chemical equations of the reactions.

Question

Philoid · Accepted Answer

i. When lead nitrate reacts with potassium iodide, it forms a yellow coloured precipitate of lead iodide along with potassium nitrate.

ii. This type of reaction is a double displacement reaction.

iii. [PbNO₃]₂ + 2KI → 2KNO₃ + PbI₂

Here,

PbNO₃ is lead nitrate.

KI is potassium iodide.

KNO₃ is potassium nitrate.

PbI₂ is lead iodide.

OR

i. X is Cu.

Y is CuO.

ii. This a redox chemical reaction. Here, copper gets oxidised by heating to copper oxide, and hydrogen reduces copper oxide back to copper.

iii. Cu + O₂ → 2CuO

CuO + H₂ → Cu + H₂O