Question

Химия 8 класс Расписать подробно 40 баллов К 145 граммам 3%-ного раствора уксусной кислоты добавили еще 20 граммов уксусной кислоты. Рассчитайте массовую долю уксусной кислоты в полученном растворе. Затем из полученного раствора выпарили 40 граммов воды. Какой стала массовая доля кислоты в растворе?​

Answer 1

Ответ:

14,(75)% когда ещё не выпарили воды

а когда выпарили массовая доля стала 20,2

Answer 2

To calculate the mass fraction of acetic acid in the solution, we need to consider the initial solution and the solution after evaporation.

Initial Solution:

- The initial solution consists of 145 grams of a 3% acetic acid solution and an additional 20 grams of acetic acid. - To calculate the mass fraction of acetic acid in the initial solution, we need to determine the total mass of acetic acid and the total mass of the solution.

1. Total mass of acetic acid: - The initial solution contains 3% acetic acid, which means that 3 grams of acetic acid are present in every 100 grams of the solution. - Therefore, the initial solution contains (3/100) * 145 = 4.35 grams of acetic acid. - In addition, 20 grams of acetic acid were added to the solution. - So, the total mass of acetic acid in the initial solution is 4.35 + 20 = 24.35 grams.

2. Total mass of the solution: - The initial solution has a mass of 145 grams. - Therefore, the total mass of the solution is 145 grams.

3. Mass fraction of acetic acid in the initial solution: - The mass fraction of a component in a solution is calculated by dividing the mass of the component by the total mass of the solution and multiplying by 100%. - In this case, the mass fraction of acetic acid in the initial solution is (24.35/145) * 100% = 16.79%.

Solution after Evaporation:

- After evaporating 40 grams of water from the solution, we need to calculate the new mass fraction of acetic acid.

1. Mass of acetic acid after evaporation: - Since acetic acid does not evaporate, the mass of acetic acid remains the same as in the initial solution, which is 24.35 grams.

2. Mass of the solution after evaporation: - The mass of the solution after evaporation is the initial mass of the solution minus the mass of water evaporated. - Therefore, the mass of the solution after evaporation is 145 - 40 = 105 grams.

3. Mass fraction of acetic acid in the solution after evaporation: - The mass fraction of acetic acid in the solution after evaporation is calculated by dividing the mass of acetic acid by the total mass of the solution and multiplying by 100%. - In this case, the mass fraction of acetic acid in the solution after evaporation is (24.35/105) * 100% = 23.19%.

Summary: - The mass fraction of acetic acid in the initial solution is 16.79%. - After evaporating 40 grams of water from the solution, the mass fraction of acetic acid in the solution becomes 23.19%.