Question

A solution is prepared by mixing 0.10 of 0.12 M sodium chloride with 0.23 L of a 0.18 M magnesium chloride solution. What is the pCl- of the resulting solution?

Answer 1

pCl⁻ = 0.54

Step-by-step explanation:

First we calculate how many Cl⁻ moles are coming from each substance, using the given volumes and concentrations:

• 0.12 M NaCl * 0.10 L = 0.012 mol NaCl = 0.012 mol Cl⁻

• 0.18 M MgCl₂ * 0.23 L = 0.0414 mol MgCl₂ = (0.0414 * 2) 0.0828 mol Cl⁻

The final volume of the mixture is = 0.10 L + 0.23 L = 0.33 L

Now we calculate [Cl⁻], using the total number of Cl⁻ moles and the final volume:

• [Cl⁻] = (0.012 mol + 0.0828 mol) / 0.33 L = 0.29 M

Finally we calculate the pCl⁻ of the resulting solution:

• pCl⁻ = -log[Cl⁻]

• pCl⁻ = 0.54