Answer:
(4) 2.0 M CaCl₂(aq).
Explanation:
- Adding solute to water elevates the boiling point.
- The elevation in boiling point (ΔTb) can be calculated using the relation:
<em>ΔTb = i.Kb.m,</em>
where, ΔTb is the elevation in boiling point.
i is the van 't Hoff factor.
- van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.
Kb is the molal elevation constant of water.
m is the molality of the solution.
<u><em>(1) 1.0 M KCl(aq):</em></u>
i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.
suppose molarity = molality, m = 1.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(1.0 m) = 2(Kb).
<u><em>(2) 2.0 M KCl(aq):</em></u>
i for KCl = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.
suppose molarity = molality, m = 2.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (2)(Kb)(2.0 m) = 4(Kb).
<u><em>(3) 1.0 M CaCl₂(aq):</em></u>
i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.
suppose molarity = molality, m = 1.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(1.0 m) = 3(Kb).
<u><em>(4) 2.0 M CaCl₂(aq):</em></u>
i for CaCl₂ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.
suppose molarity = molality, m = 2.0 m,
∴ ΔTb for (1.0 M KCl) = i.Kb.m = (3)(Kb)(2.0 m) = 6(Kb).
- <em>So, the aqueous solution has the highest boiling point at standard pressure is: (4) 2.0 M CaCl₂(aq).</em>
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