Heat required to melt $1\, g$ of ice is $80\, cal$. $A$ man melts $60\, g$ of ice by chewing in one minute. His power is ........ $W$.

The ratio between kinetic energy and the total energy of the electrons of a hydrogen atom according to Bohr's model is

Honey bees also produce beeswax,which finds many uses in industry,such as:

Particles of masses $m, 2m, 3m, \ldots, nm$ grams are placed on the same line at distances $l, 2l, 3l, \ldots, nl$ $cm$ from a fixed point. The distance of the centre of mass of the particles from the fixed point in centimetres is

Half-life of a radioactive substance is $20 \, min$. The difference between the time when it is $33 \%$ disintegrated and $67 \%$ disintegrated is approximately ......... $min$.

Ammonia acts as a ligand but ammonium ion does not form complexes because