Calculate the mass of the precipitate that forms when an aluminum chloride solution is exposed

univerkov | April 29, 2021 | education

Calculate the mass of the precipitate that forms when an aluminum chloride solution is exposed to a 150 g sodium hydroxide solution with a mass fraction of 10%.

Given:

m (NaOH) = 150 g

w% (NaOH) = 10%

To find:

m (draft) -?

Decision:

AlCl3 + 3NaOH = 3NaCl + Al (OH) 3, – we solve the problem, focusing on the composed reaction equation:

1) Find the mass of the alkali that has reacted:

m (NaOH) = 150 g * 0.1 = 15 g.

2) Find the amount of alkali:

n (NaOH) = m: M = 15 mol: 40 g / mol = 0.375 mol.

3) We compose a logical expression:

If 3 mol of NaOH gives 1 mol of Al (OH) 3,

then 0.375 mol of NaOH will give x mol of Al (OH) 3,

then x = 0.125 mol.

4) Find the mass of Al (OH) 3 precipitated:

m (Al (OH) 3) = n * M = 0.125 mol * 78 g / mol = 9.75 g.

Answer: m (Al (OH) 3) = 9.75 g.

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