Question

a chemist prepares a solution of magnesium fluoride (mgf₂) by measuring out 7.6 mg of magnesium fluoride into a 100. ml volumetric flask and filling the flask to the mark with water. calculate the concentration in mol/l of the chemists magnesium fluoride solution. round your answer to 2 significant digits. mol/l

Explanation:

Step1: Convert mass to grams

Given mass of \(MgF_2\) is \(m = 7.6\space mg\). Since \(1\space mg=10^{- 3}\space g\), then \(m = 7.6\times10^{-3}\space g\).

Step2: Calculate molar mass of \(MgF_2\)

The molar mass of \(Mg\) is \(M_{Mg}=24.305\space g/mol\), and the molar mass of \(F\) is \(M_{F} = 19.00\space g/mol\). For \(MgF_2\), \(M = 24.305+(2\times19.00)=62.305\space g/mol\)

Step3: Calculate the number of moles of \(MgF_2\)

Using the formula \(n=\frac{m}{M}\), where \(m\) is mass and \(M\) is molar mass. So \(n=\frac{7.6\times 10^{-3}\space g}{62.305\space g/mol}\approx1.22\times10^{-4}\space mol\)

Step4: Convert volume from mL to L

Given volume \(V = 100.\space mL\). Since \(1\space L = 1000\space mL\), then \(V=\frac{100.}{1000}\space L = 0.100\space L\)

Step5: Calculate the concentration (molarity)

Using the formula \(c=\frac{n}{V}\), where \(c\) is concentration, \(n\) is number of moles and \(V\) is volume. So \(c=\frac{1.22\times 10^{-4}\space mol}{0.100\space L}=1.2\times10^{-3}\space mol/L\)

Answer:

\(1.2\times 10^{-3}\space mol/L\)