What is the molarity of each ion in a solution of (a) 2.0 M NaCl and (b) 0.40 M K2SO4 Assume complete dissociation.

Question

What is the molarity of each ion in a solution of (a) 2.0 M NaCl and (b) 0.40 M [latex]K_2SO_4[/latex] Assume complete dissociation.

Accepted Answer

(a) According to the dissociation equation,

[latex]NaCl \xrightarrow[]{H_2O} Na^+(aq) + Cl^-(aq)[/latex]

1 mol 1 mol 1 mol

the concentration of [latex]Na^+[/latex] is equal to that of NaCl : 1 mol NaCl → 1 mol [latex]Na^+[/latex] and the concentration of [latex]Cl^-[/latex] is also equal to that of NaCl Therefore the concentrations of the ions in 2.0 M NaCl are 2.0 M [latex]Na^+[/latex] and 2.0 M [latex]Cl^-[/latex]

(b) According to the dissociation equation

[latex]K_2SO_4 \xrightarrow[] {H_2O} 2K^+(aq) + SO^{2-}_4(aq)[/latex]

1 mol 2 mol 1 mol

the concentration of [latex]K^+[/latex] is twice that of [latex]K_2SO_4[/latex] and the concentration of [latex]SO_4^{2-}[/latex] is equal to that of [latex]K_2SO_4[/latex] .Therefore the concentrations of the ions in 0.40 M [latex]K_2SO_4[/latex] are 0.80 M [latex]K^+[/latex] and 0.40 M [latex]SO_4^{2-}[/latex]

Question 15.2: What is the molarity of each ion in a solution of (a) 2.0 M ...

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