There are 34 g of oxygen in the container.
We can use the<em> Ideal Gas Law</em> to solve this problem.
But
, so
and

STP is 0 °C and 1 bar, so

The correct option is C. The amount of MgCl2. we know this because <span>no matter how much you increase KOH, if you dont increase Mgcl2, the amount of Mg(OH)2 remains the same. Hope this works for you</span>