HI
So, the formula for water is H2O
When you have the same amount of the reactants , hydrogen will be the limiting reactant.
Limiting reactant is the thing that runs out first.
The term that best described a 10 gram of KClO3 per 100 grams of water solution at 30 degree Celcius is Saturated. The solubility chart is needed for this work. If the solubility chart is drawn for KClO3, it will be observed that the proportion of KClO3 that is needed to dissolve in 100ml of water to make the solution saturated is 10 grams at 30 degree Celcius.
This is an application of Boyle's law:
P₁V₁ = P₂V₂. we don't have to convert volume and pressure to standard forms. we can even use the pressure with mmHg
1 atm = 760 mmHg
V₂ = P₁V₁ / P₂ = 745 x 500 / 760 = 490 ml
Note that here we assume constant temperature