Question

Сколько граммов воды нужно испарить из 500 г 10%-ного раствора гидроксида натрия, чтобы увеличить его концентрацию в 1,5 раза? Ответ укажите в граммах с точностью до целых.

Answer 1

исходный раствор содержит 300*0,15 = 45 г твердого КОН
конечный раствор имеет концентрацию в 15*2=30% при том же кол-ве твердого КОН в 45 грамм. Или это 45/0,3= 150 г раствора
имеем:
300 г исходного раствора, содержащего 45 г КОН и 300-45=255 г Н2О
150 г конечного раствора, содержащего 45 г КОН и 150-45=105 г Н2О
итого, надо выпарить 255-105=150 г воды

Answer 2

Calculation of Water Evaporation

To calculate the amount of water that needs to be evaporated from a 500 g 10% solution of sodium hydroxide to increase its concentration by 1.5 times, we need to follow these steps:

1. Determine the initial concentration of the sodium hydroxide solution: - The initial concentration is given as 10%. - This means that in a 500 g solution, there are 10% or 50 g of sodium hydroxide.

2. Calculate the final concentration of the sodium hydroxide solution: - To increase the concentration by 1.5 times, we multiply the initial concentration by 1.5. - Final concentration = 10% * 1.5 = 15%.

3. Determine the final mass of the sodium hydroxide in the solution: - The final mass of sodium hydroxide can be calculated by multiplying the final concentration by the total mass of the solution. - Final mass of sodium hydroxide = 15% * 500 g = 75 g.

4. Calculate the amount of water that needs to be evaporated: - The difference between the initial mass of sodium hydroxide (50 g) and the final mass of sodium hydroxide (75 g) represents the amount of water that needs to be evaporated. - Amount of water to be evaporated = Final mass of sodium hydroxide - Initial mass of sodium hydroxide = 75 g - 50 g = 25 g.

Therefore, 25 grams of water need to be evaporated from the 500 g 10% solution of sodium hydroxide to increase its concentration by 1.5 times.