Find the number of sodium chloride molecules in 260 g of a 40% solution.

Let us determine what mass of salt is present in the specified solution, when from the condition of the task we know that this solution is 40%:

260 * 40: 100 = 104.

As we know from the school chemistry curriculum, the number of moles of a substance can be determined by the ratio of its mass to its molar mass.

Determine how many moles of trusted salt are contained in our solution:

v = m / M;

M (NaCL) ≈ 58 g / mol;

v = 104: 58 ≈ 1.793 mol.

Determine the number of molecules by multiplying by Avogadro’s constant:

1.793 * 6.02 * 10 ^ 23 = 10.79386 * 10 ^ 23.

Answer: 10.79386 * 10 ^ 23.