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 dissolved 10.1 gMass of aqueous solution (c = 4.18 J/gºC) 100. gT initial 30.0ºCT final 21.6ºCMolar mass of KNO3 101 g/molWhich of the following equations correctly shows the heat of solution (kJ/mol) for the dissolving of KNO3?KNO3(s) --> K+(aq) + NO3-(aq) + 3510 kJKNO3(s) --> K+(aq) + NO3-(aq) + 8.4 kJKNO3(s) + 35.1 kJ --> K+(aq) + NO3-(aq)KNO3(s) +3.51 kJ --> K+(aq) + NO3-(aq)

Answer 1

Answer:

Equation correctly showing the heat of solution

$KNO_3(s)+35.2 kJ \rightarrow K^+(aq) + NO_{3}^-(aq)$

Explanation:

Mass of aqueous solution = m = 100 g

Specific heat of solution = c = 4.18 J/gºC

Change in temperature = $\Delta T=T_f-T_i$

ΔT = 21.6ºC - 30.0ºC = -8.4ºC

Heat lost by the solution = Q

$Q = mc\Delta T$

$Q=100 g\times 4.18 J/g^oC\times (-8.4^oC)$

Q = -3,511.2 J ≈ -3.51 kJ

Heat absorbed by potassium nitrate when solution in formed; Q'

Q' = -Q = 3.51 kJ

Moles of potassium nitrate , n= $\frac{10.1 g}{101 g/mol}=0.1 mol$

$KNO_3(s)\rightarrow K^+(aq) + NO_{3}^-(aq)$

The heat of solution =

$\frac{Q'}{n}=\frac{3.5112 kJ}{0.1 mol}=35.1 kJ/mol$

So, the equation correctly showing the heat of solution

$KNO_3(s)+35.2 kJ \rightarrow K^+(aq) + NO_{3}^-(aq)$