Maher H. answered • 02/25/21

Highly Experienced Math, Science, MCAT, and Test Prep Tutor

So to figure this out, first we need to write the decomposition reaction

2KClO_{3} --> 2KCl + 3O_{2}

From this equation we see that it takes 2 moles of KClO_{3} to make 3 moles of O_{2}The molar mass of KClO_{3} is 122.5g.

So now let's turn grams of KClO_{3 }into moles of O_{2. }

30.6g x 1mol KClO_{3 }/ 122.5g x 3 moles O_{2} / 2 mol KClO_{3 }= 0.375 moles O_{2}

At STP, we know 1 mole of any gas has a volume of 22.4L. So, we just multiply the moles of oxygen by 22.4L and we get 8.4L