Question

11. Сколько килограммов пресной воды нужно добавить к 10 кг морской воды, чтобы её солёность упала с 5% до 2%? Солёность это процентное содержание соли в растворе.​

Answer 1

Ответ: 40 кг морской воды содержит 5% соли, что составляет 40*0,05=2 кг соли

Либо:       40 кг    -    100%

                х       -       5%       х=40*5:100=2 кг

Пошаговое объяснение: Теперь 2 кг соли - это будет 2%, а 100% составляет  р кг соли

           2 кг     -     2%

             р       -    100%        р=2*100:2=100 кг

Значит к 40 кг морской воды надо добавить 100-40=60 кг пресной воды.

Вот ответ

Пошаговое объяснение:

Answer 2

Calculation of Freshwater Needed to Reduce Salinity

To calculate the amount of freshwater needed to reduce the salinity of 10 kg of seawater from 5% to 2%, we can use the concept of mass balance. The total mass of the solution (seawater + freshwater) remains constant throughout the process.

Let's assume that x kg of freshwater needs to be added to the 10 kg of seawater. The resulting solution will have a total mass of (10 + x) kg.

According to the problem, the initial salinity of the seawater is 5%, which means that 5% of the total mass of the seawater is salt. Similarly, the final salinity is 2%, which means that 2% of the total mass of the resulting solution is salt.

Using the concept of mass balance, we can set up the following equation:

Salt mass in seawater = Salt mass in resulting solution

The salt mass in the seawater is 5% of 10 kg, which is 0.05 * 10 kg = 0.5 kg.

The salt mass in the resulting solution is 2% of (10 + x) kg, which is 0.02 * (10 + x) kg.

Setting up the equation:

0.5 kg = 0.02 * (10 + x) kg

Simplifying the equation:

0.5 = 0.02 * (10 + x)

Dividing both sides by 0.02:

25 = 10 + x

Subtracting 10 from both sides:

x = 25 - 10

x = 15 kg

Therefore, 15 kg of freshwater needs to be added to 10 kg of seawater to reduce its salinity from 5% to 2%.