A student puts his signature with graphite pencil. If the mass of carbon in the signature is 10^-12 g, calculate the number of carbon atoms in the signature.

An unknown gas shows a density of 3 g per litre at 273°C and 1140 mm Hg pressure. What is the gram molecular mass of this gas?

Calculate the number of molecules in one kg of NaOH.

Calculate the number of atoms present in :

(a) 10 g of Chlorine

(b) 10 g of Nitrogen