Question

Сколько граммов 75%-ного раствора кислоты надо добавить к 30 г 15%-ного раствора кислоты, чтобы получить 50 %-ный раствор кислоты?

Answer 1

Надо так:
в 15-% расстворе кислоты есть 25,5 грамм воды и 4,5 грамма кислоты.
т.е. всего 30 грамм.
Пусть надо добавить х грамм кислоты и у грамм воды.Тогда
4,5 +х=25,5+у
в 75-% растворе масса кислоты в 3 раза больше чем воды, т.е. х=3у
4,5 +3у=25,5+у
2у=21
у=10,5
х=31,5
всего надо добавить х+у грамм 75-% раствора кислоты, т.е. х+у=10,5+31,5=42

Answer 2

Calculating the Amount of 75% Acid Solution Needed

To calculate the amount of 75% acid solution needed to add to 30g of 15% acid solution to obtain a 50% acid solution, we can use the following formula:

Amount of 75% acid + Amount of 15% acid = Total amount of 50% acid

Let's denote: - Amount of 75% acid as x (in grams) - Amount of 15% acid as 30 grams

Using the formula, we can set up the equation: 0.75x + 0.15(30) = 0.50(x + 30)

Solving for x will give us the amount of 75% acid solution needed.

Solving the Equation

Using the equation 0.75x + 0.15(30) = 0.50(x + 30), we can solve for x:

0.75x + 4.5 = 0.50x + 15

Subtracting 0.50x from both sides: 0.25x + 4.5 = 15

Subtracting 4.5 from both sides: 0.25x = 10.5

Dividing by 0.25: x = 42

So, 42 grams of the 75% acid solution need to be added to 30 grams of the 15% acid solution to obtain a 50% acid solution.

Therefore, to obtain a 50% acid solution, 42 grams of the 75% acid solution should be added to 30 grams of the 15% acid solution.