How many grams of water and salt do you need to take to prepare 40 g of an 8% solution?

The mass of the solution is 40 grams;
To find the mass of salt, it is necessary to multiply its mass fraction by the mass of the solution.
m salt = 40 x 0.08 = 3.2 grams;
To find the mass of water, subtract the mass of salt from the mass of the solution:
m of water = 40 – 3.2 = 36.8 grams;
The density of water is 1 gram / cm3. To prepare this solution, you must measure out 36.8 milliliters of water.
Check: 36.8 + 3.2 = 40;

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