Question

Определите массу 30% ого раствора некоторой соли, необходимую для приготовления 400 г 10% ого раствора.

Answer 1

W=mв-ва/mр-ра
mв-ва=0,1*400=40 г
mр-ра=40/0,3=133,3 г

Answer 2

Calculating the Mass of 30% Solution Needed

To determine the mass of a 30% solution of a certain salt required to prepare a 400g 10% solution, we can use the following approach:

1. Calculate the Mass of the Salt in the 10% Solution: - The 10% solution contains 10% of the salt and 90% of the solvent. - Therefore, the mass of the salt in the 10% solution can be calculated as 10% of 400g.

2. Calculate the Mass of the Salt in the 30% Solution: - The 30% solution contains 30% of the salt and 70% of the solvent. - We need to find the mass of the 30% solution that contains the same amount of salt as the 10% solution.

3. Find the Difference: - Subtract the mass of the salt in the 10% solution from the mass of the salt in the 30% solution to determine the additional mass of the salt needed.

Let's proceed with the calculations.

Solution

1. Calculate the Mass of the Salt in the 10% Solution: - Mass of salt in the 10% solution = 10% of 400g - Mass of salt in the 10% solution = 0.10 * 400g - Mass of salt in the 10% solution = 40g

2. Calculate the Mass of the Salt in the 30% Solution: - Let's denote the mass of the 30% solution needed as 'x' grams. - Mass of salt in the 30% solution = 30% of x - Mass of salt in the 30% solution = 0.30x

3. Find the Difference: - Additional mass of the salt needed = Mass of salt in the 30% solution - Mass of salt in the 10% solution - Additional mass of the salt needed = 0.30x - 40g

To find the value of 'x', we can set up the equation: - 0.30x - 40g = 0 - 0.30x = 40g - x = 40g / 0.30 - x = 133.33g

Conclusion

To prepare a 400g 10% solution, you would need approximately 133.33 grams of the 30% solution of the salt.