Neco 2019 Chemistry Question 37

Practice objective / multiple choice question 37 from the 2019 Neco Chemistry examination.

Neco 2019 Chemistry Objective / Multiple Choice Medium Difficulty
Question 37 NECO • 2019 • CHEMISTRY • objective

At 20°C the solubility of sodium chloride (NaCl) is 0.018 mol·L\(^{-1}\) and at 30°C it is 0.010 mol·L\(^{-1}\). (a) Using these data, calculate the standard enthalpy change \(\Delta H^{\circ}\) for the dissolution process (in kJ·mol\(^{-1}\)) assuming the van't Hoff relation applies. (b) A solution is prepared by mixing 250.0 mL of the 20°C saturated NaCl solution with 250.0 mL of a 0.0050 M Na\(^+\) solution. When the mixture is heated to 30°C, how many grams of NaCl precipitate? (Molar mass of NaCl = 58.44 g·mol\(^{-1}\)).

Answer Options

A. ΔH° = -95.3 kJ·mol⁻¹; mass precipitated ≈ 6.2×10⁻³ g
B. ΔH° = -86.7 kJ·mol⁻¹; mass precipitated ≈ 1.2×10⁻² g
Correct Answer C. ΔH° = -86.7 kJ·mol⁻¹; mass precipitated ≈ 5.0×10⁻³ g
D. ΔH° = +86.7 kJ·mol⁻¹; mass precipitated ≈ 5.0×10⁻³ g
Correct Answer
C
Correct Option:
ΔH° = -86.7 kJ·mol⁻¹; mass precipitated ≈ 5.0×10⁻³ g

About This Question

This is Neco 2019 Chemistry Question 37. It is one of the objective questions from the 2019 Neco Chemistry examination.

Difficulty level: Medium .

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