Gas Stoichiometry at STP


You want to calculate the number of moles H2O that form from 13.5 L O2, assuming the reaction ​is at STP.

Use the dimensional analysis below to set up the two-step calculation.

Ratio 1
\mathsf{\frac{1\,mol\, O_2}{22.4\, L\, O_2}}

Ratio 2
\mathsf{\frac{22.4\, L\, O_2}{1\,mol\, O_2}}

Ratio 3
\mathsf{\frac{2\, mol\, H_2O}{5\, mol\, O_2}}

Ratio 4
\mathsf{\frac{5\, mol\, O_2}{2\, mol\, H_2O}}
​Which ratio should be used for the first conversion, from liters O₂ to moles O₂?

Ratio 1

Ratio 3

Ratio 4

Ratio 2