Question

РЕБЯТА ПРОШУ ПОМОЧЬ.РЕШАЕТСЯ МОЯ СУДЬБА!!!!! Лаборанту необходимо получить 40г 20% серной кислоты. В наличии имеется 30% и 5% кислоты. Сколько каждой кислоты нужно взять (по массе) для получения необходимого раствора? Возможные ответы, но нужно решение 1) 16 г и 24 г. 2) 24 г и 16 г. 3) 12 г и 20 г. [!!!] Если вы понимаете хотябы как решать, прошу под ответ посмотреть и решить правильно. Ну очень нужно [!!!]

Answer 1

Ответ 2 - 24 г 30% р-ра + 16 г 5% р-ра

Answer 2

Problem Analysis

The lab assistant needs to obtain 40g of a 20% sulfuric acid solution. They have two different concentrations of sulfuric acid available: 30% and 5%. The task is to determine how much of each acid should be taken to obtain the desired solution.

Solution

To solve this problem, we can set up a system of equations based on the principles of mass and concentration.

Let's assume that x grams of the 30% sulfuric acid solution is taken and y grams of the 5% sulfuric acid solution is taken.

# Equation 1: Mass of sulfuric acid

The total mass of sulfuric acid in the resulting solution should be equal to 40g: x * 0.30 + y * 0.05 = 40

# Equation 2: Concentration of sulfuric acid

The concentration of sulfuric acid in the resulting solution should be 20%: (x * 0.30 + y * 0.05) / (x + y) = 0.20

Simplifying Equation 2: 0.30x + 0.05y = 0.20(x + y) 0.30x + 0.05y = 0.20x + 0.20y 0.10x = 0.15y x = 1.5y Now, we can substitute Equation 2 into Equation 1 to solve for the values of x and y.

Substituting x = 1.5y into Equation 1: (1.5y * 0.30) + (y * 0.05) = 40 0.45y + 0.05y = 40 0.50y = 40 y = 80

Substituting y = 80 into x = 1.5y: x = 1.5 * 80 x = 120

Therefore, the lab assistant needs to take 120g of the 30% sulfuric acid solution and 80g of the 5% sulfuric acid solution to obtain the desired 40g of a 20% sulfuric acid solution.

Answer

The lab assistant should take 120g of the 30% sulfuric acid solution and 80g of the 5% sulfuric acid solution to obtain the desired 40g of a 20% sulfuric acid solution. Therefore, the correct answer is 2) 24g and 16g.