Question

A 35.0 mL sample of 1.00 M KBr and a 60.0 mL sample of 0.600 M KBr are mixed. The solution is then heated to evaporate water until the total volume is 50.0 mL. What is the molarity of KBr in the final solution?

Answer 1

Answer: The molarity of KBr in the final solution is 1.42M

Explanation:

We can calculate the molarity of the KBr in the final solution by dividing the total number of moles of KBr in the solution by the final volume of the solution.

We will first calculate the number of moles of KBr in the individual sample before mixing together

In the first sample:

Volume (V) = 35.0 mL

Concentration (C) = 1.00M

Number of moles (n) = C × V

n = (35.0mL × 1.00M)

n= 35.0mmol

For the second sample

V = 60.0 mL

C = 0.600 M

n = (60.0 mL × 0.600 M)

n = 36.0mmol

Therefore, we have (35.0 + 36.0)mmol in the final solution

Number of moles of KBr in final solution (n) = 71.0mmol

Now, to get the molarity of the final solution , we will divide the total number of moles of KBr in the solution by the final volume of the solution after evaporation.

Therefore,

Final volume of solution (V) = 50mL

Number of moles of KBr in final solution (n) = 71.0mmol

From

C = n / V

C= 71.0mmol/50mL

C = 1.42M

Therefore, the molarity of KBr in the final solution is 1.42M