Name KEY with Assignment 25 Practice – Thermodynamics …

Name_______________________________________________ Assignment 25 Practice – Thermodynamics II CP2120 Fall 2020 Write legibly, show calculations, and use the correct chemical symbols and formatting for full credit. 1. Convert 435 calories to energy in joules. 2. Look up the number of calories in one tablespoon of

olive oil. How many joules of energy are obtained from 1 tablespoon of olive oil? Keep in mind that one dietary calorie (1 Cal) is equal to 1000 scientific calories (1000 cal = 1 kcal).

3. If an expanding gas inside a cylinder does 305 J of

work pushing a piston up against gravity, and the gas gives off 175 joules of heat, what is the change in internal energy of the gas?

4. Deduce the mathematical sign of q or w for each of

the following statements and write the value. a. “The block of copper metal gave off 250 joules

of heat”

b. “The endothermic reaction absorbed 50 joules of heat”

c. “Running for ten seconds, this hair dryer puts out 5 kilojoules of heat.”

d. “Sounds unbelievable, but that weightlifter raised 350 kg by 80 cm in a deadlift!”

e. “I used about 78 calories of energy to push the piston down and compress the gas.” (write two answers, one for the person and one for the gas.

5. How much work is performed on or by a gas that is compressed from 8.0 liters to 4.0 liters under an external pressure of 1.0 atm?

6. Glucose, C6H12O6, has an enthalpy of combustion of

DcH = -2803 kJ/mol. a. Write the balanced chemical equation. b. What is the heat of combustion for the burning of

2.00 mol of glucose? c. What is the heat of combustion for the production of

30 moles of water?

7. When powdered aluminum metal is mixed with

powdered iron (II) oxide and the mixture is ignited, solid aluminum oxide and 2 moles of pure iron are formed. This reaction releases approximately 850 kJ/mol of heat. Write the thermochemical equation for this process.

8. How much energy is released during the formation

of 100 g of ammonia from the elements?

2 2 3N ( ) + 3H ( ) 2NH ( ); = –91.8 kJg g g H¾¾® D

KEY answerswithcorrectnumber ofSrgfigs

435Cat4.184J 1,820 J I tiatm I JICANw PAV

115 125Calpickanumber 1.0atm4.0L 8.0DW 4,0 Latin

if Icat4.184Jthen1kcals4.184KJ CatinoG 60dg 7602cg166120cL120Callikat4.184151 502KJlKeats

5.0 102KJ a

2.002mi 2803151 5606KIIMOI 5610150IN qt w C175J 1 f305J

480J Phase usestandardstate4.80102 J 30m04 2803 14,015KJ 104KJ6mots

ironAIDq 250 J

qs 50J FED3671211167 AKO36312FELDDrHs850KJmoi

q 5 KJ

IN Mgh 350kg9.8067m520,8m2745,88kgm252 052 molarmassofammonia36.002947 14.00674 9mo

10094,4amggygxz9l.m8oykI 269.52KJW person 78cal 300KJW gas 78 cal