MEDIUM
8th CBSE
IMPORTANT
Earn 100
Graphite is used as a solid lubricant. Give reasons.
Important Questions on Carbon and its Compounds
MEDIUM
8th CBSE
IMPORTANT
How does a dry powder type fire extinguisher work?
HARD
8th CBSE
IMPORTANT
A naturally occurring minerals of sedimentary rocks on heating to high temperatures decomposes giving a solid 'A' and a gas. The solid on dissolution in water undergoes chemical reactions which is associtated with hissing sound and the solution appears to be boiling. Compound 'B' formed during this reaction on long standing forms a layer of white powder. When excess is passed through this milky white solution, a clear solution is formed again. Identify the substances and justify the above observations. Give reasons wherever required.
MEDIUM
8th CBSE
IMPORTANT
In the manufacture of silicon carbide by Acheson process, sawdust is used along with sand and coke in the electric furnace. What is the main purpose of using sawdust as one of the constituents of the mixture?
MEDIUM
8th CBSE
IMPORTANT
The genuineness of a pearl can be verified by dipping it in lemon juice. Why?
MEDIUM
8th CBSE
IMPORTANT
Why does fogging occur while using a soda-acid fire extinguisher?
HARD
8th CBSE
IMPORTANT
With what material are pencil leads made of? Justify its usage and also explain why it is called 'lead'. Also, explain why different pencils give different shades of darkness?
MEDIUM
8th CBSE
IMPORTANT
Why is wood charcoal considered to be an excellent household fuel?
HARD
8th CBSE
IMPORTANT
Two compounds X and Y, when dissolved in water, produced sodium bicarbonate. If hydrochloric acid is added to compound X, compound Y is liberated. Identify X and Y.
