Question

solution equals the mass of whats dissolved divided by the total volume of the solution.
heres how the student prepared the solution:

• the label on the graduated cylinder says:

empty weight: 5.000 g

• she put some solid sodium hydroxide into the graduated cylinder and weighed it. with the sodium hydroxide added, the cylinder weighed 40.53 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 119.86 ml.

what concentration should the student write down in her lab notebook? be sure your answer has the correct number of significant digits.
g·ml⁻¹

Explanation:

Step1: Calculate mass of sodium hydroxide

The mass of sodium hydroxide $m$ is the mass of the cylinder with sodium hydroxide minus the empty - weight of the cylinder. So $m = 40.53\ g-5.000\ g = 35.53\ g$.

Step2: Calculate concentration

The concentration $C$ of the solution is given by the mass of the solute divided by the volume of the solution. So $C=\frac{m}{V}$, where $m = 35.53\ g$ and $V = 119.86\ mL$. Then $C=\frac{35.53\ g}{119.86\ mL}\approx0.2964\ g\cdot mL^{-1}$.

Answer:

$0.2964\ g\cdot mL^{-1}$