Question

a chemist prepares a solution of calcium bromide (cabr₂) by measuring out 19.7 μmol of calcium bromide into a 250. ml volumetric flask and filling the flask to the mark with water.
calculate the concentration in mmol/l of the chemists calcium bromide solution. round your answer to 3 significant digits.

Explanation:

Step1: Convert micromoles to millimoles

We know that \(1\space\mu mol = 10^{- 3}\space mmol\). Given \(n = 19.7\space\mu mol\) of \(CaBr_{2}\), then \(n=19.7\times10^{-3}\space mmol\)

Step2: Convert volume from milliliters to liters

We know that \(1\space L=10^{3}\space mL\). Given \(V = 250.0\space mL\), then \(V=\frac{250.0}{10^{3}}\space L = 0.2500\space L\)

Step3: Calculate the concentration

The formula for concentration \(C=\frac{n}{V}\). Substituting \(n = 19.7\times10^{-3}\space mmol\) and \(V = 0.2500\space L\) into the formula, we get \(C=\frac{19.7\times 10^{-3}\space mmol}{0.2500\space L}\)

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Answer:

\(7.88\times 10^{-2}\space mmol/L\)