In 400 g of a 25% solution of caustic potassium, 45 liters of carbon dioxide were dissolved. Find the mass of the resulting salt.

Given:
m solution (KOH) = 400 g
w (KOH) = 25% = 0.25
V (CO2) = 45 l
To find:
m (K2CO3)
Decision:
2KOH + CO2 = K2CO3 + H2O
m in islands (KOH) = w * m solution = 0.25 * 400 g = 100 g
n (KOH) = m / M = 100 g / 56 g / mol = 1.79 mol
n (CO2) = V / Vm = 45 l / 22.4 l / mol = 2 mol
Because KOH is in short supply, then
n (KOH): n (K2CO3) = 2: 1
n (K2CO3) = 1.79 mol / 2 = 0.895 mol
m (K2CO3) = n * M = 0.895 mol * 138 g / mol = 123.51 g
Answer: 123.51 g