Question

What is the mass of 3 moles of $O_2$?

Answer 1

Given: No. of moles (n)$O_2$ = 3 moles

Number of moles(n) =Given mass(m)/Molar mass(M)
So, Given mass = Number of moles $\times$ molar mass

Molar mass $O_2$(M) = 32g

Mass of 3 moles of $O_2$ = nM

= 3$\times$32

= 96g