Answer:
The answers are: (a )0.0058 M; (b) 0.00681 M; (c) 0.006912 M
Explanation:
Ionic strenght= μ= 1/2 ∑ c z²
Where c is the concentration of each ion (in M) and z is the charge of the ion. So, to calculate the ionic strenght of a solution you have to know the concentration of each ion and their charges. For this, the dissociation equilibrium is required.
a) HCl → H⁺ + Cl⁻
Conc H⁺= 0.00580 M
Conc Cl⁻= 0.00580 M
μ= 1/2 x ((Conc H⁺)(+1)²) + ((Conc Cl⁻)(-1)²
μ= 1/2 x ((0.00580 M) + (0.00580 M))
μ= 0.00580 M
b) CaBr₂ → Ca²⁺ + 2 Br⁻
Conc Ca²⁺= 0.00227 M
Conc Br⁻= 2 x 0.00227 M= 0.00454 M
μ= 1/2 ((Conc Ca²⁺)(+2)² + ((Conc Br⁻)(-1)²)
μ= 1/2 (0.00227 M (4)) + (0.00454 M)
μ= 0.00681 M
c) The solution has two dissociation equilibria:
Mg(NO₃)₂ → Mg²⁺ + 2 NO₃⁻
La(NO₃)₃ → La³⁺ + 3 NO₃⁻
Conc Mg²⁺= 0.000752 M
Conc NO₃⁻= 2 x (0.000752 M) + 3 x (0.000776 M)= 0.003832 M
Conc La³⁺= 0.000776 M
μ= 1/2 ((Conc Mg²⁺)(+2)²)+ ((Conc NO₃⁻)(-1)²) + ((Conc La³⁺)(+3)²)
μ= 1/2 (0.000752 M(4)) + (0.003832 M) + (0.000776 M)(9))
μ= 0.006912 M
