Question

KNO3(s) --> K+(aq) + NO3-(aq)This reaction was carried out in a Styrofoam insulated calorimeter and the following data were recorded:Mass of solid KNO3 dissolved10.1 gMass of aqueous solution (c = 4.18 J/gºC)100. gT initial30.0ºCT final21.6ºCMolar mass of KNO3101 g/molWhich of the following equations correctly shows the heat of solution (kJ/mol) for the dissolving of KNO3?KNO3(s) + 35.1 kJ --> K+(aq) + NO3-(aq)KNO3(s) +3.51 kJ --> K+(aq) + NO3-(aq)KNO3(s) --> K+(aq) + NO3-(aq) + 8.4 kJKNO3(s) --> K+(aq) + NO3-(aq) + 3510 kJ

Answer 1

Answer:

KNO₃(s) + 35.1 kJ ⇒ K⁺(aq) + NO₃⁻(aq)

Explanation:

In the solution of KNO₃, solid KNO₃ dissolves and ionizes into aqueous K⁺(aq) and NO₃⁻(aq). Since the final temperature (21.6 °C) is lower than the initial temperature (30.0°C), the reaction is endothermic.

The heat absorbed (Q) is:

Q = c(sol) . m(sol) . ΔT = (4.18 J/g. °C) × 100g × (30.0 °C - 21.6 °C) = 3511 J = 3.51 kJ

The heat absorbed per mole of KNO₃ is:

$\frac{3.51kJ}{10.1g} .\frac{101g}{mol} =35.1kJ/mol$

The resulting equation is:

KNO₃(s) + 35.1 kJ ⇒ K⁺(aq) + NO₃⁻(aq)