What is the mass of the salt obtained by passing carbon dioxide through 400 g of a 20% sodium hydroxide solution?

Given:

m (NaOH) = 400 g

w% (NaOH) = 20%

To find:

m (salt) -?

Solution:

1) We compose the reaction equation corresponding to the condition of the problem:

2NaOH + CO2 = Na2CO3 + H2O;

2) Find the mass of sodium hydroxide in the solution:

m (NaOH) = 400 g * 0.2 = 80 g;

3) Find the amount of sodium hydroxide:

n (NaOH) = m: M = 80 g: 40 g / mol = 2 mol;

4) We compose logical equality:

if 2 mol gives 1 mol,

then 2 mol will give x mol,

then x = 1 mol, – a tautology is possible in the calculations.

5) Find the mass of sodium carbonate obtained during the reaction:

m (Na2CO3) = n * M = 1 mol * 106 g / mol = 106 g.

Answer: m (Na2CO3) = 106 g.