the equation is,

2KCL0subscipt3--->2KCL+3Osubscript2

if 5.0 g of KCLOsubscript3 is decomposed, what volume of 0subcript2 is produced at STP?

Write the equation and balance it.

2KClO3 ==> 2KCl + 3O2

1. Convert g KClO3 to moles. # moles = grams/molar mass.
2. Using the coefficients in the balanced equation, convert moles KClO3 to moles O2.
3. Convert moles O2 to volume remembering at STP that 22.4 L/mole x # moles = ?? L.
Post your work if you get stuck.