Question

5) A 35.6 g sample of ethanol (C2HsOH) is burned in a bomb calorimeter, according to the following on. If the temperature rose from 35.0 to 76.0°C and the heat capacity of the calorimeter is 23.3 kJ/PC, what is the value of AHrxn? The molar mass of ethanol is 46.07 gmol C2HsOH)+302() 2 Co2()+3 H20) frxn7 A) -1.24 x 103 kJ/mol C)-809 x 103 kJ/rnol B) +1.24 x 103 kJ/mol E) +9.55 x 103 kJ/mol D) -9.55 x 103 kJ/mol Qana when qna--qeal oqrxn-. (955 U)--955 kj qeal Cal x T qcal-23.3 klC x (76.0-35.0-C cal 955 kJ 1 mol C,H OH 46.07 g C2HsOH mol C,HsOH? -35.6 g CH,OHx 0.773 mol COH Qraen 955 kJ AHan in kJ/mol?- --1.24x 103 kJ/mol n0.773 mol 6) When 21.45 g of potassium nitrate, KNOj, was dissolved in water in a calorimeter, the temperature fell from 25.00 °C to 14.14°C. If the heat capacity of the calorimeter is 0.505 kJ/°C, what will be the ?? for the solution process? KNOj(s) K (ag)+ NOj (aq)

Answer 1

Heat capacity of calorimeter, C = 0.505 kJ/degree C Change in temperature produced, AT = 14.14 degree C - 25.00 degree C = - 10.86 degree C Amount of heat released in the reaction is equal to the heat absorbed by the calorimeter. ix (- 10.86 degree C CAT 0.505 kJ+ 5.4843 kJMass of KN03 = 21.45 g No of moles of KNOj = 21.45 g x1 mo1 KN degree 3 101. lg + 5.4843 kJ 0.2122 mol + 25.84 kJ mol 0.2122 mol KNO,Enthalpy change,AH