Question

2.800 г раствора с массовой долей соли равной 1% упарили до 400 г. Определите массовую долю соли в полученном растворе и массу испарившейся воды.

Answer 1

W=m/M
w-массовая доля
m-масса соли 
M-масса раствора
отсюда масса соли
m=0.01*2800=28 г
найдём массовую долю соли в растворе после упаривания
w1=(28/400)*100%=7%
масса воды в 1 растворе равна 2800г-28г=2772 г
масса воды в 2 растворе 400-28=372 г
Найдём массу испарившейся воды m=2772-372=2400г

Answer 2

1 найдем массу соли в исходном растворе w=(2800*1%)/100%=28 грамм.
Соль из раствора не испаряется, следовательно её масса равна исходной, по формуле w= (mв-ва/m р-ра)*100%, масса конечного раствора равно 400, следовательно w= (28/400)*100%= 7%
масса воды=2800-400=2400 грамм

Answer 3

Problem Analysis

We are given that 2.800 g of a solution with a salt mass fraction of 1% is evaporated to obtain a residue of 400 g. We need to determine the mass fraction of salt in the resulting solution and the mass of evaporated water.

Solution

To solve this problem, we can use the concept of mass fraction. The mass fraction of a component in a solution is the ratio of the mass of that component to the total mass of the solution.

Let's calculate the mass of salt in the original solution and the mass of water in the original solution.

Step 1: Calculate the mass of salt in the original solution. Given: - Mass of the original solution = 2.800 g - Salt mass fraction in the original solution = 1%

The mass of salt can be calculated as follows: ``` Mass of salt = Mass of the original solution * Salt mass fraction = 2.800 g * 0.01 = 0.028 g ```

Step 2: Calculate the mass of water in the original solution. Given: - Mass of the original solution = 2.800 g - Mass of salt in the original solution = 0.028 g

The mass of water can be calculated as follows: ``` Mass of water = Mass of the original solution - Mass of salt = 2.800 g - 0.028 g = 2.772 g ```

Step 3: Calculate the mass fraction of salt in the resulting solution. Given: - Mass of the resulting solution = 400 g - Mass of salt in the resulting solution = 0.028 g

The mass fraction of salt can be calculated as follows: ``` Mass fraction of salt = Mass of salt in the resulting solution / Mass of the resulting solution = 0.028 g / 400 g = 0.00007 ```

Step 4: Calculate the mass of evaporated water. Given: - Mass of the original solution = 2.800 g - Mass of the resulting solution = 400 g - Mass of water in the original solution = 2.772 g

The mass of evaporated water can be calculated as follows: ``` Mass of evaporated water = Mass of water in the original solution - Mass of water in the resulting solution = 2.772 g - (Mass of the resulting solution - Mass of salt in the resulting solution) = 2.772 g - (400 g - 0.028 g) = 2.772 g - 399.972 g = 0.828 g ```

Answer

Therefore, the mass fraction of salt in the resulting solution is approximately 0.00007 and the mass of evaporated water is approximately 0.828 g.

Please note that the calculations are approximate due to rounding.