The volume of mixture of 2gms of helium and 7gms of nitrogen under STP conditions of

A) 22.4lit B) 11.2lit
C) 16.8 D) 5.6lit

2 answers

2g*(1 mole/4.003g)=0.5 moles of He

7g*(1 mole/14.01g)=0.5 moles of N

Together we have a total of 1 mole of gas.

At STP, 1 mole of a gas has a volume of 22.4L. That is just a relationship that you must commit to memorization.
Options (c)