Question

If 200. mL of 0.60 M MgCl2(aq) is added to 400 mL of distilled water, what is the concentration of Mg and Cl in the resulting solution?
A. 0.20 M Mg ion & 0.20 M Cl ionB. 0.40 M Mg ion & 0.40 M Cl ionC. 0.20 M Mg ion & 0.40 M Cl ionD. 2.0 M Mg ion & 2.5 M Cl ion

Answer 1

Answer:

C. 0.20 M Mg ion & 0.40 M Cl ion

Explanation:

MgCl₂ is a ionic salt which is dissociated as this

MgCl₂  →  Mg²⁺  +  2Cl⁻

First of all, we have a solution of 200 mL, with [MgCl₂] = 0.6M

Molarity . volume = moles.

0.6 mol/l . 0.2l = 0.12 mol

  MgCl₂  →  Mg²⁺  +  2Cl⁻

0.12mol      0.12         0.24

This moles are also in 400mL of water, so the new concentration is

[Mg²⁺] = 0.12 m/0.6L = 0.2M

[Cl⁻] = 0.24 m/0.6L = 0.4M

Remember we initially have 200mL and then, we add 400 mL, so we supose aditive volume. (600mL)