Question

Какую массу воды необходимо выпарить из 500 г 4% раствора гидроксида калия, чтобы получить 10% раствор этой щелочи? Ответ_____г. (с точностью до целых)

Answer 1

Ну тут если я не ошибаюсь, выходит 12,78 г (я не уверена что правильно)

Answer 2

Calculation of Water Evaporation

To calculate the mass of water that needs to be evaporated from a 500 g 4% solution of potassium hydroxide to obtain a 10% solution of the same alkali, we can use the following approach:

Let's assume that the initial mass of the potassium hydroxide in the 4% solution is X grams. Since the solution is 4% potassium hydroxide, we can write the equation:

X grams of potassium hydroxide / 500 grams of solution = 4% (or 0.04)

From this equation, we can find the value of X:

X = 500 grams of solution * 0.04

Now, let's assume that Y grams of water need to be evaporated to obtain a 10% solution of potassium hydroxide. The final mass of the potassium hydroxide in the 10% solution can be calculated as follows:

X grams of potassium hydroxide / (500 grams of solution - Y grams of water) = 10% (or 0.1)

From this equation, we can find the value of X:

X = (500 grams of solution - Y grams of water) * 0.1

Since the initial mass of potassium hydroxide is the same in both equations, we can equate the two expressions for X:

500 grams of solution * 0.04 = (500 grams of solution - Y grams of water) * 0.1

Simplifying the equation:

20 = 10 - 0.02Y

0.02Y = 10 - 20

0.02Y = -10

Y = -10 / 0.02

Y = 500

Therefore, 500 grams of water need to be evaporated from the 500 g 4% solution of potassium hydroxide to obtain a 10% solution of the same alkali.

Please note that the negative value obtained for Y indicates that the given concentration cannot be achieved by evaporating water from the solution. It is likely that additional potassium hydroxide would need to be added to reach the desired concentration.