Magnesium metal was placed in 400 g of a 30% phosphoric acid solution.

Magnesium metal was placed in 400 g of a 30% phosphoric acid solution. How much hydrogen is released in this case.

Determine the mass of phosphoric acid.

m = 400 * 0.3 = 120 g / mol.

Let’s write down the reaction equation.

2Н3РО4 + 3Mg = Mg3 (PO4) 2 + 3H2.

Determine the amount of phosphoric acid substance.

M (H3PO4) = 98 g / mol.

n = m / M.

n = 120/98 = 1.2 mol.

Let’s determine the amount of hydrogen substance and volume.

1.2 mol – x mol.

2 mol – 3 mol.

X = 1.8 mol.

V = 1.8 * 22.4 = 40.32 liters of hydrogen.