Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them.

(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminum fluoride

Find out the correct sentence about manure

(i) Manure contains large quantities of organic matter and small quantities of nutrients.

(ii) It increases the water holding capacity of sandy soil.

(iii) It helps in draining out of excess of water from clayey soil.

(iv) Its excessive use pollutes environment because it is made of animal excretory waste.

‘Osmosis is a special kind of diffusion’ comment.

Write the molecular formulae for the following compounds

(a) Aluminum (III) nitrate

(b) Calcium (II) phosphate

(c) Mercury (II) chloride

(d) Magnesium (II) acetate

Helium atom has 2 electrons in its valence shell but its valency is not 2, Explain.