magnesium chlorate under goes decompostion, oxgen gas is realsed in the following reaction:

2KClO3 → 2KCl + 3O2

when 3.50 grams of potassuim chlorate is decomposed at STP, how many litters of oxgen will be produced?

2 answers

Two errors to point out. You say magnesium chlorate but use potassium chlorate. Second, L is liters, not litters (as in a litter of puppies).

Convert grams KClO3 to mols. mols = grams/molar mass
Using the coefficients in the balanced equation, convert mols KClO3 to mols O2.
Then convert mols O2 to L. 22.4 L/mol x mols = ?L
It will be 22.4 x 3/2 x the moles of KClO3

moles KClO3= 3grams/molmasspotassiumchlorate