# Calculate the mass of salt that can be formed by the interaction of magnesium oxide, weighing 16 g

Calculate the mass of salt that can be formed by the interaction of magnesium oxide, weighing 16 g and hydrochloric acid, weighing 21.3 g.

Let’s write down given:
m (MgO) = 16 g
m (HCl) = 21.3 g
m (salt) -?
Decision.
1) We write the equation for the reaction of the interaction of magnesium oxide with hydrochloric acid:
MgO + 2HCl = MgCl 2 + H2O
2) Let’s calculate the amount of substance of each of the reacting substances:
M (MgO) = 24 + 16 = 40 g / mol
n (MgO) = 16 g / 40 g / mol = 0.4 mol
M (HCl) = 1 + 35.5 = 36.5 g / mol
n (HCl) = 21.3 g / 36.5 g / mol = 0.58 mol
3) Find a substance that is in excess:
According to the reaction equation, 1 mol (MgO) interacts with 2 mol (HCl)
This means that 0.8 mol (HCl) is needed for 0.4 mol (MgO), and we have 0.58 mol of acid, therefore, it is in short supply and we make the calculation using hydrochloric acid.
M (MgCl2) = 24 + 2 * 35.5 = 95 g / mol
2 * 36.5 g (HCl) forms 95 g (MgCl2)
21.3 g (HCl) forms x g (MgCl2)
X = 95g * 21.3g / 2 * 36.5g
X = 27.72 g (MgCl2)