Question

A chemistry student must write down in her lab notebook the concentration of a solution of sodium hydroxide. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution. Here's how the student prepared the solution: The label on the graduated cylinder says: She put some solid sodium hydroxide into the graduated cylinder and weighed it. With the sodium hydroxide added, the cylinder weighed 13.195 g. She added water to the graduated cylinder and dissolved the sodium hydroxide completely. Then she read the total volume of the solution from the markings on the graduated cylinder. The total volume of the solution was 127.53 mL. What concentration should the student write down in her lab notebook? Be sure your answer has the correct number of significant digits.

Answer 1

Empty cyclinder weight = 1.5 g

After addition of sodium hydroxide into cylinder weight = 13.195 g

sodium hydroxide weight, which was put in cyclinder = 13.195-1.5 = 11.695 g

Total volume of the solution = 127.53 ml

Molarity = (Wt/MWt)x(1000/V in ml) = (11.695/40)x(1000/127.53) = 11695/5101.2 = 2.292 g/mL

The concentration of solution of sodium hydroxide = 2.292 g/mL