Determine the mass fraction of caustic soda in the solution formed by the interaction of 4.6 g

Determine the mass fraction of caustic soda in the solution formed by the interaction of 4.6 g of sodium with 150 g of water.

2Na + 2H2O = 2NaOH + H2

First, let’s calculate the number of moles of the starting reagents.

n (Na) = m (Na) / M (Na) = 4.6 / 23 = 0.2 mol

n (H2O) = m (H2O) / M (H2O) = 150/18 = 8.3 mol

There is a large excess of water, which means that we carry out further calculations for sodium.

Let’s calculate the number of moles of the formed caustic soda NaOH.

n (NaOH) = n (Na) = 0.2 mol

Let’s calculate the mass of alkali.

m (NaOH) = n (NaOH) * M (NaOH) = 0.2 * 40 = 8 g

w (NaOH) = m (NaOH) / M (Na + H2O) = 8 / (150 + 4.6) * 100% = 5.2%