Which of the following fertilisers contains the least percentage of nitrogen?

Heating of orthophosphoric acid to about 900°C, produces

A. Metaphosphoric acid

B. Pyrophosphoric acid

C. No change in it

D. None of these

A potassic fertiliser contains 50% K₂O. It could be

A. Potassium sulphate

B. Potassium chloride

C. A mixture of NaCl + KCl

D. None of these

Liquid ammonia is not used as such a fertiliser in tropical countries like India, because

A. Its N₂ content is very low

B. It is very costly

C. It will evaporate on spraying

D. It is not available

Which one of the following is used as a nitrogenous fertiliser, as a weed killer in the onion fields and for correcting acidic soils?

A. Urea

B. CAN

C. Ammonium sulphate

D. Calcium cyanamide