Question

a chemistry student must write down in his lab notebook the concentration of a solution of potassium chloride. the concentration of a 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: 4.25 g he put some solid potassium chloride into the graduated cylinder and weighed it. with the potassium chloride added, the cylinder weighed 61.646 g. he added water to the graduated cylinder and dissolved the potassium chloride completely. then he read the total volume of the solution from the markings on the graduated cylinder. the total volume of the solution was 123.46 ml. what concentration should the student write down in his lab notebook? be sure your answer has the correct number of significant digits

Explanation:

Step1: Calculate mass of potassium chloride

The mass of potassium chloride ($m$) is the mass of the cylinder with the substance minus the empty - weight of the cylinder. So, $m = 61.646\ g-4.25\ g = 57.396\ g$.

Step2: Calculate the concentration of the solution

The concentration ($C$) of a solution is given by the formula $C=\frac{m}{V}$, where $m$ is the mass of the solute and $V$ is the volume of the solution. Here, $V = 123.46\ mL$. So, $C=\frac{57.396\ g}{123.46\ mL}\approx0.465\ g/mL$.

Answer:

$0.465\ g\ mL^{-1}$