Calculate the final concentration: Water is added to 0.25 L of a 5.5 M NaF solution to make 2.6 L of a diluted NaF solution.

Question

Express your answer to two significant figures and include the appropriate units.

Answer 1

The simplest way to approach this problem is to determine the number of moles of sodium fluoride in the initial solution. You are given that you have 0.25 L of a 5.5 M solution. Recall that M = molar = moles/liter.

Therefore, (0.25 L) * (5.5 moles NaF/L) = 1.375 moles of NaF.

By adding water, you have not changed the number of moles of NaF in the solution. Therefore, since you finished with 2.6 L, the new concentration is

(1.375 moles NaF)/(2.6 L) = 0.5288 M solution. You are asked to express the answer to two significant figures and include appropriate units, so the final answer is

0.53 M NaF solution or 0.53 moles NaF/L