Question

A 40% solution of sodium chloride contains 20g sodium chloride . Calculate the amount of water present in this solution

Answer 1

So first we will calculate the amount of NaCl in the first solution:

w(NaCl) = m(NaCl)/ m(solution)

40% = m(NaCl)/ 60g

40/100 = m(NaCl)/ 60g

m(NaCl) = 60*40/ 100

m(NaCl) = 24g

After this we will calculate the amount of NaCl in the second solution:

w(NaCl) = m(NaCl)/ m(solution)

15% = m(NaCl)/ 100g

15/100 = m(NaCl)/ 100g

m(NaCl) = 15*100/ 100

m(NaCl) = 15g

Now when we now the amounts of sodium chloride in each of the solutions, we can say that the final solution will be 160g containing 39g of sodium chloride.

To find the mass percent of NaCl in this final solution, we will use the formula, we used above:

w(NaCl) = m(NaCl)/ m(solution)

w(NaCl) = 39g/ 160g

w(NaCl) = 0.24375

w(NaCl) = 24.375%

w(NaCl) = 24.4%

So the mass percent of sodium chloride in the final solution is 24.4%