A 4.691 g sample of MgCl₂ is dissolved in enough water to give 750.mL of solution.What is the magnesium ion concentration in this solution? A)3.70 × 10^-2 M B)1.05 × 10^-2 M C)6.57 × 10^-2 M D)4.93 × 10^-2 M E)0.131 M

Question

Quizplus · Accepted Answer

To find the magnesium ion concentration in the solution, we need to first calculate the number of moles of MgCl2 present in the solution.

m(MgCl2) = 4.691 g

The molar mass of MgCl2 = 95.21 g/mol

Number of moles of MgCl2 = m(MgCl2) / Molar mass(MgCl2)

Number of moles of MgCl2 = 4.691 g / 95.21 g/mol = 0.04928 mol

Now, we need to calculate the concentration of Mg2+ ions in the solution.

Molarity of Mg2+ = (0.04928 mol / 0.750 L) = 0.0657 M = 6.57 × 10^-3 M

Since magnesium chloride dissociates into Mg2+ and Cl- ions, the concentration of magnesium ions in the solution is equal to 6.57 × 10^-3 M or 6.57 × 10^-2 mM. Therefore, the best choice is C.

A 4691 G Sample of MgCl2 Is Dissolved in Enough Water

A 4691 G Sample of MgCl₂ Is Dissolved in Enough Water