When magnesium nitrate was heated, 5.6 liters of oxygen was released, calculate the mass of decomposed salt.

1. The decomposition of magnesium nitrate is described by the equation:

2Mg (NO3) 2 = 2MgO + 4NO2 ↑ + O2 ↑;

2. Let’s calculate the chemical amount of released oxygen:

n (O2) = V (O2): Vm = 5.6: 22.4 = 0.25 mol;

3. Determine the amount of decomposed salt:

n (Mg (NO3) 2) = n (O2) * 2 = 0.25 * 2 = 0.5 mol;

4. Calculate the mass of magnesium nitrate:

m (Mg (NO3) 2) = n (Mg (NO3) 2) * M (Mg (NO3) 2);

M (Mg (NO3) 2) = 24 + 2 * 14 + 6 * 16 = 148 g / mol;

m (Mg (NO3) 2) = 0.5 * 148 = 74 g.

Answer: 74 g.