When magnesium nitrate is heated, oxygen is released V = 5.6 l Calculate the mass of the salt obtained.

First, we compose an equation for this problem, which looks like this:
Mg (NO3) 2 = Mg (NO2) 2 + O2
Next, we find the amount of oxygen, for this we divide the volume of oxygen by the molar volume.
n (Mg (NO3) 2) = n (O2) = V (O2) / Vm = 5.6 / 22.4 = 0.25 mol
Further, knowing the amount of the substance, we calculate the mass of the resulting salt, for this we multiply the amount of the substance by the molar mass and the result is the following solution:
m (Mg (NO3) 2) = nxM = 0.25×148 = 37 g
we get that the mass of salt is 37 grams.