Among the following identify the molecules with gram molecular mass 44 g.

 Gram molecular mass of a molecule is defined as the weight of 1 mole of molecule that is represented in grams.

Let us see the gram molecular mass of each molecule

The gram molecular mass of ${\mathrm{CO}}_2$is find as given below.

GMW = 1(C)+2(O)

=1(12g)+2(16g)=44g

The gram molecular mass of ${\mathrm{NO}}_2$ is find as given below.

GMW=1(N)+2(O)

=1(14g)+2(16g)=46g

The gram molecular mass of ${\mathrm{C}}_3{\mathrm{H}}_8$ is find as given below.

GMW=3(C)+8(H)

=3(12g)+8(1g)=44g

The gram molecular mass of ${\mathrm{N}}_2\mathrm{O}$ is find as given below.

GMW=1(N)+2(O)

=2(14g)+1(16g)

=44g

Therefore, the molecules with gram molecular mass as 44 g are ${\mathrm{CO}}_2,{\mathrm{C}}_3{\mathrm{H}}_8 \mathrm{and} {\mathrm{N}}_2\mathrm{O}$