2NaNO3 --> 2NaNO2 + O2. When a sample of solid sodium nitrate was heated 96cm3 of gas was collected, calculate the mass of NaNO3 Decomposed

We know that the reaction is a 2:1 ratio as 2 moles of NaNO3 is used to form 1 mole of O2 so first we need to find the moles of the product produced 
SoVolume of gas (dm3)= number of moles x 24dm3Therefore volume of gas = 96cm3 = 0.096dm3Moles of NaN2O2 = 0.096/24 = 0.004 moles Therefore moles of NaNO3 is also 0.008 moles Mr of NaNO3 = 32 + 16 + 16 + 16 = 71Mass = Mr x moles Mass = 71 x 0.008 = 0.568 g