Find concentration

Question

What concentration of Cl- results when 871mL of 0.713 M LiCl is mixed with 677 mL of 0.377 M MgCl2?

Answer 1

The Cl- comes from two sources: the LiCl and the MgCl2. We will find the moles of Cl- from each source, then find the total volume. We will then divide the moles of Cl- by the liters to obtain mole/liter which is what is asked for.

moles Cl^- from LiCl: 871 ml x 1 L/1000 ml x 0.713 mol/L = 0.621 moles Cl^-

moles Cl^- from MgCl₂: 677 ml x 1 L/1000 ml x 0.377 mol/L x 2 mol Cl^-/mol MgCl₂ = 0.510 moles of Cl^-

Total moles of Cl^- = 0.621 + 0.510 = 1.13 moles Cl^-

Total volume in liters = 0.871 L + 0.677 L = 1.55 L

Final concentration of Cl^- = 1.13 moles / 1.55 L = 0.729 mol/L = 0.729 M