CHE112H1 Lecture Notes - Lecture 13: Enthalpy, Ideal Gas, Real Gas

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cerisegiraffe538

19 Oct 2015

School

UTSG

Department

Chemical Engineering and Applied Chemistry

Course

CHE112H1

Professor

Philip Yaneff

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Document Summary

Che112h1 - lecture 13 - chapter 8 enthalpy and heat reaction. Enthalpy is the heat flows under condition of constant pressure. Most chemical processes are done under constant pressure and volume can change. H - chemical reaction or process. H = h2 - h1 = (u2 + p2v2) - (u1 + p1v1) Up = q - p v. = (u2 - u1) + (p2v2 - p1v1) H = u + pv. H = q + w + p v = q - p v + p v = q ( u) Hp = qp constant volume process constant pressure process. Hp = qp = cp t. 1 mol liquid h2o at stp occupies 18 cm3. 1 mol water vapor at stp occupies 22400 cm3. H = cp t (heat/cool at all pressure) H = cp t (heat/cool at constant pressure)

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Question 2 Energy Calculations

a) Calculate the heat energy (q) when 12.0 g of water is heated from 20oC to 100oC. The

specific heat for water is given in your textbook.

b) Is the process of heating water exothermic or endothermic? Explain your answer.

Question 3 Energy Calculations

You dissolve 0.1 mol of ammonium nitrate in 100 mL of H2O. The temperature of the solution

changes from 22oC to 15oC. The specific heat capacity for water is 4.184 J/g.K. Show all

calculations on a separate sheet of paper!

a) Is this reaction endothermic or exothermic?

b) Calculate the heat, q, released or absorbed in the dissolution reaction.

c) Calculate the enthalpy change, ?Hrxn (kJ/mol), for dissolving 1 mol of ammonium nitrate.

Question 4. A gas expands from 264 mL to 971 mL at constant temperature. Calculate

the amount of work done in Joules by the gas when it expands against a constant pressure of 955

torr.

Question 5 Energy Calculations

a) The nutritional calorie (Calorie) is equivalent to 1 kcal. One pound (1.0 lb) of body fat is

equivalent to 4.1 x 103 kcal. Express this quantity in joules and kilojoules. Use

scientific notation for your answer!

b) If an athlete expends 1850 kJ/h (kilojoules per hour), how long does he have to exercise

to work off 1.0 lb of body fat?

c) The average amount of calories burned during running is 125 kcal/mile. How many

miles does this athlete have to run to burn off 1.0 lb of body fat?

Question 6

Calculate ?Ho for the following reactions at 298 K. Give the balanced thermochemical

equations and show the correct physical state in each equation. Calculate the enthalpy change

for each reaction. You will find thermochemical data in the back of your textbook in Appendix 3

(p. A-8 to A-12)

a) The formation of 1 mol of HCl (gas) from its elements

b) The formation of 1 mol of sodium chloride from its elements

c) The combustion of 1 mol glucose to water and carbon dioxide

d) HCl(g) + NH3(g) ? NH4Cl(g)

Question 7

Calculate heat of formation of SO2 under nonstandard state conditions, given the following

equations

SO2(g) +

CHE112H1 Lecture Notes - Lecture 13: Enthalpy, Ideal Gas, Real Gas

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