Name: Lab day/time: DUE: Week 12 at the beginning of the lab period!! Expt 11 Pr

Question

Name: Lab day/time: DUE: Week 12 at the beginning of the lab period!! Expt 11 Prelab Assignment Reading Assignment: . Lab Packet Expt 11 Determining the Solubility of KNOs in water Section 4.5 Section 6.7 Appendix 4 Concentrations of Solutions Heat of Solution Logarithms pp. A13-A14 Textbook Write a chemical equation that describes the dissolution of potassium nitrate into hydrated ions and the absorption of heat. 11a 11b How many moles of KNO, (s) are contained in 5.00 g of the substance? The specific heat capacity of water is 421/g-K· temperature increase of 25 , how much "heat energy" did it absorb? If a 50.0 g sample of water exhibited a 11c if the heat of solution is exothermic, does a compound become more soluble or less soluble when the temperature of the solution is increased? Briefly justify your answer. 11d 11e If In(S) = 4.02, what is S?

Explanation / Answer

11a ) The dissolution recation is :

KNO3(s) + H2O (l) ----> KNO3(aq) ----> K+(aq) + NO3-(aq)

11b) Number of moles of KNO3 is , n = mass/molar mass

n = 5.00 g / 101.1(g/mol)

= 0.05 moles

99c) Amount of heat , Q = mcdt

Where

m = mass of water = 50.0 g

c = specific heat capacity of water = 4.2 J/gK

dt = change in temperature = 25 oC

Plug the values we get Q = 5250 J

11e) Given lnS = 4.02

---> S = e4.02

= 55.7

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