![\textsf{\qquad\qquad\huge\underline{{\sf Answer}}}](https://img.qammunity.org/2023/formulas/mathematics/high-school/trhnafi81eej17382z2z5tyjdk0rj5l4im.png)
As per the given equation, we can infer that :
For getting 2 moles mole of water, 1 mole of oxygen gas was required. so to get 4 moles of water we need :
We just have to multiply the whole reaction by 2 on both sides, in order to get 4 moles of H2O on product side.
![\qquad \qquad \rm4 \: H_2 + 2 \: O_2 \rightarrow4 \: H_2O](https://img.qammunity.org/2023/formulas/chemistry/high-school/8eepmialvwj5amwphrrj67mjf8xj5ptnp4.png)
therefore, we need
![\qquad \sf \dashrightarrow \: 2 * 1 = 2 \: moles \: \: oxygen \: gas](https://img.qammunity.org/2023/formulas/chemistry/high-school/8xpdv5a5ww5qatgo7x9n153dj2f53hcpar.png)