Gives reasons as to why :
(i) almost 90 % of all known compunds are organic in nature.
(ii) it is dangerous to burn methane in an insufficient supply of air.

Almost 90% of all known compounds are organic in nature. Give reason.

Give reasons why dilute sulphuric acid (i) behaves as an acid when dilute (ii) is dibasic in nature.

Give reasons for the following : (i) Methane does not undergo addition reactions, but ethene does. (ii) Ethyne is more reactive than ethane. (iii) Hydrocarbons are excellent fuels.

Fill in the blanks with correct word/symbol to make it a true statement: (i) A triangle has .. sides. (ii) A triangle has ..vertices. (iii) A triangle has ..angles. (iv) A triangle has ..parts. (v) A triangle whose no two side are equal is known as.. (vi) A triangle whose two sides are equal is known as (vii) A triangle whose all the sides are equal is known as (viii) A triangle whose one angle is a right angle is known as. (ix) A triangle whose all the angles are of measure less than 90^0 is known as (x) A triangle whose one angle is more than 90^0 is known as.....

Give reasons for each of the following: (i) Size of trivalent lanthanoid cation decreases with increase in the atomic number. (ii) Transition metal fluorides are ionic in nature whereas bromides and chlorides are usualy covalent in nature. (iii) Chemistry of all the lanthanoids is quite similar.

Give reasons for the following : (i) Metals can be recovered from their ores by chemical methods. (ii) High purity metals can be obtained by zone refining method. (iii) Why is sodium choride added during electrolysis of fused anhydrous magnesium chloride ? (iv) Why is chalcocite roasted and not calcinated during recovery of copper ?

Give reasons why : (i) most zygotes in angiosperms divide only after certain amount of endosperm is formed. (ii) ground nut seeds are exalbuminous and castor seeds are albuminous. (iii) Micropyle remains as a small pore in the seed coat of a seed. (iv) integuments of an ovule harden and the water content is highly reduced,as. the seed matures. apple and cashew are not called true fruits.

Give reasons for i] alkanes are said to be saturated organic compounds ii] alkenes are known as olefins iii) alkenes are more reactive than alkanes iv) ethanoic acid is known as an aliphatic monocarboxylic acid.

State , giving reasons , which of the following pairs of sets are disjoint sets : (i) A = { natural numbers multiples of 3 and less than 28 and (ii) B = { natural numbers divisible by 4 and between 19 and 40 }

Answer the following with relevant reason. (i)Xenon has closed shell configuration but is known to give compounds with fluorine. (ii)The boiling points of noble gases increase with increase in atomic number. (iii)Why helium and neon do not form clathrate compounds with quinol ?