Question

Из раствора массой 700 г массовой долей нитрата калия 15% выпариванием удалили 400г воды. Какова массовая доля хлорида калия в новом растворе? Помогите, пожалуйста. За лето все забыла

Answer 1

W1(KNO3)=15%
m(KNO3)=700*0.15=105г
w2(KNO3)=105/300/100%=35%

Answer 2

Calculation of the Mass Fraction of Potassium Chloride in the New Solution

To calculate the mass fraction of potassium chloride in the new solution, we need to consider the initial solution and the amount of water that was evaporated.

Given: - Mass of the initial solution = 700 g - Mass fraction of potassium nitrate in the initial solution = 15% - Mass of water evaporated = 400 g

To find the mass fraction of potassium chloride in the new solution, we need to determine the mass of potassium chloride and the total mass of the new solution.

1. Calculate the mass of potassium nitrate in the initial solution: - Mass of potassium nitrate = Mass of the initial solution * Mass fraction of potassium nitrate - Mass of potassium nitrate = 700 g * 0.15 = 105 g

2. Calculate the mass of potassium chloride in the initial solution: - Since the initial solution only contains potassium nitrate and water, the remaining mass is potassium chloride. - Mass of potassium chloride = Mass of the initial solution - Mass of potassium nitrate - Mass of potassium chloride = 700 g - 105 g = 595 g

3. Calculate the total mass of the new solution: - The total mass of the new solution is the mass of potassium chloride plus the mass of water that was not evaporated. - Total mass of the new solution = Mass of potassium chloride + Mass of water remaining - Total mass of the new solution = 595 g + (700 g - 400 g) = 895 g

4. Calculate the mass fraction of potassium chloride in the new solution: - Mass fraction of potassium chloride = Mass of potassium chloride / Total mass of the new solution - Mass fraction of potassium chloride = 595 g / 895 g ≈ 0.665

Therefore, the mass fraction of potassium chloride in the new solution is approximately 0.665 or 66.5%.

Please note that the calculation assumes that the mass of the solute (potassium nitrate and potassium chloride) does not change during the evaporation process.