Question

a chemist prepares a solution of potassium chloride (kcl) by measuring out 0.24 g of kcl into a 250. ml volumetric flask and filling to the mark with distilled water. calculate the molarity of cl^- anions in the chemists solution. be sure your answer has the correct number of significant digits.

Explanation:

Step1: Calculate the moles of KCl

The molar mass of \(KCl\) is \(M = 39.10\ g/mol+35.45\ g/mol = 74.55\ g/mol\).
Using the formula \(n=\frac{m}{M}\), where \(m = 0.24\ g\) and \(M = 74.55\ g/mol\), we have \(n=\frac{0.24\ g}{74.55\ g/mol}\approx0.00322\ mol\).

Step2: Determine the volume of the solution

The volume of the solution \(V = 250\ mL=0.250\ L\) (since \(1\ L = 1000\ mL\)).

Step3: Calculate the molarity of \(KCl\)

Using the formula \(C=\frac{n}{V}\), where \(n = 0.00322\ mol\) and \(V = 0.250\ L\), we get \(C=\frac{0.00322\ mol}{0.250\ L}=0.0129\ M\).

Step4: Relate \(KCl\) molarity to \(Cl^-\) molarity

Since \(KCl = K^++Cl^-\), the molarity of \(Cl^-\) is equal to the molarity of \(KCl\).

Answer:

\(0.013\ \frac{mol}{L}\)