Question

Q.17. (a) A piece of black electrode used in dry cell on strong heating in air gave a
colorless gas which turned lime water -milky. What was the material of the
electrode?
(b) Why does graphite conducts electricity, but diamond not?
OR
(a) Draw the structure of propanoic acid (C2H3COOH).
(b) Why does the bottom of a cooking vessel blacken?
(c) What is a micelle? Draw a labelled diagram of a micelle.​

Answer 1

Answer

a) Since the colourless gas evolved turns lime water milky, the gas is carbon dioxide.

Carbon on strong heating in air releases carbon dioxide, hence the material of the electrode was carbon.

b) 3 Carbon atoms join together to form ring like structure in graphite. Hence 1 electron is free. Due to this free electron, graphite conducts electricity.

OR

a) Propanoic acid has a formula $\sf C_2H_5COOH$ (Refer attachment)

b) Bottom of cooking vessels get blackened due to deposition of unburnt carbon particles. Incomplete combustion of carbon occurs when there is lack of air (oxygen) for burning.

c) Micelles are structure formed by soap molecules where one end of the soap molecule is towards the oil droplet or dirt (hydrophobic tail) and the other ionic end faces outside (hydrophilic head).

Refer attachment for diagram.

Answer 2

Answer:

17(a)

Explanation:

It converts lime water milky means Carbon dioxide or Carbon is present...

Here the piece of black electrose is Graphite(Lead) which is an allotrope of Carbon