a) Calculate the mass of $112 \mathrm{L} {\mathrm{CO}}_2$ gas kept at STP (molecular mass $=44$)

b) How many molecules of ${\mathrm{CO}}_2$ are present in it?

The molecular mass of ammonia is $17$.

a) How much is the GMM of ammonia?

b) Find out the number of moles of molecules present in $170 \mathrm{g}$ of ammonia.

c) Calculate the number of ammonia molecules present in the above sample of ammonia?

The molecular mass of oxygen is $32$.

a) What is the GMM of ${\mathrm{O}}_2$?

b) How many moles of molecules are there in $64 \mathrm{g}$ of oxygen? How many molecules are there in it?

c) Calculate the number of oxygen atoms present in $64 \mathrm{g}$ of oxygen?

Examine the samples given.

a. $20 \mathrm{g} \mathrm{He}$           b. $44.8 \mathrm{L}$ of ${\mathrm{NH}}_3$ at STP

c. $67.2 \mathrm{L} {\mathrm{N}}_2$ at STP          d. $1$ mole of ${\mathrm{H}}_2{\mathrm{SO}}_4$        e. $180 \mathrm{g}$ of water.

i) Arrange the samples in the increasing order of the number of molecules in each. 
ii) What will be the ascending order of the number of atoms? 
iii) What will be the mass of samples b, c, and d?