1-30

1. Objects can possess energy as:

(b) potential energy & (c) kinetic energy BOTH

10. ΔH for the reaction IF5 (g) IF3 (g) + F2 (g) is __________ kJ, given the data below. IF (g) + F2(g) IF3 (g) ) ΔH = -390 kJ IF (g) + 2F2(g) IF5 (g) ΔH = -745 kJ

+355

16. Which of the following is not true?

-Liquid water at 100°C causes more severe burns than water vapour at 100°C. -When water vapour at 100°C condenses to liquid, the phase change releases a large amount of heat. ***BOTH

21. A student determined the heat of fusion of water to be 366.9 J/g. If the accepted value is 333.3J/g, what is the student's percent error?

10.0% ***SEE Calculation Set value and then multiplying by 100. Calculated value - accepted value / accepted value x 100 = 366.9 - 333.6 / 333.6 x 100 = 33.3 / 333.6 x 100 = 10%

20. How many joules of heat are absorbed when 70.0 grams of water is completely vaporized at its boiling point?

158,130 ***SEE Calculation Set The heat of vaporization for water is 2259 J/g. Multiply heat of vaporization by the grams to find the calories absorbed in vaporizing water. 70 g x 2259 J/g = 158, 130 J.

26. How many changes of state are represented in this graph?

2

6. The specific heat capacity of lead is 0.13 J/g-K. How much heat (in J) is required to raise the temperature of 15g of lead from 22 °C to 37 °C?

29

24. How many states of matter are represented in this graph?

3

7. A 50.0-g sample of liquid water at 25.0 C is mixed with 29.0 g of water at 45.0 °C. The final temperature of the water is __________.

32.3

19. How many joules are equivalent to 35 kilojoules?

35,000 joules ***SEE Calculation Set kilo means 103 or 1000. 35 x 1000 = 35,000 joules.

8. The value of H0 for the reaction below is -72 kJ. __________ kJ of heat are released when 1.0 mol of HBr is formed in this reaction: H2(g) + Br2 (g) 2HBr(g)

36

15. How much heat is absorbed by 2.00 kg of water at 20°C if it is heated until it is converted completely into water vapour?

5.2E3 kJ ***Remember the "K"

9. Which of the following is a statement of Hess's Law?

If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the sum of the enthalpy changes for the individual steps.

11. Which of the following is true of a cooling curve showing the conversion of liquid water to ice cubes?

Temperature is shown on the y-axis

13. Which of the following does not occur when liquid water freezes to form ice?

The average kinetic energy of the particles changes.

22. A student using a Styrofoam cup as a calorimeter added a piece of metal to distilled water and stirred the mixture. a) The initial temperature of 50.0 g of water was 25°C. b) The initial temperature of 20.0 g of metal was 100 °C. c) The final temperature of the water and metal was 32.0° C

The water "gained 350" calories of heat and the metal lost 350 calories of heat. ***SEE Calculation Set Heat flows from hot to cold. Since the initial temp. of the water is colder than that of the metal, the metal will lose heat while the water gains heat. Eliminate answers 1 and 2. Amount of heat flow or H = m x change in temp H = mass of water x 32°C - 25°C (initial water temp) or H = 50 x 7 = 350 calories of heat gained by the water. Heat loss must equal heat gain. Therefore the metal lost 350 cal of heat while the water gained 350 cal of heat.

18. Solid X is placed in contact with solid Y. Heat will flow spontaneously from X to Y when

X is 10°C and Y is 5°C

25. During what segments does the graph show increasing kinetic energy (motion)?

a, c, and e

14. The flat portion of a heating curve occurs

at either the melting point or the boiling point

27. What letter represents the temperature at the Melting Point (mp) of this substance?

b

28. During what segments does the graph show no increase in kinetic energy (motion), but there is increasing potential energy?

b and d

29. The substance is all liquid in what segment?

c

30. The substance is both liquid and a gas... and energy is being used by atoms/molecules to leave the liquid and become gaseous in what segment?

d

5. The reaction 4Al(s) + 3O2 (g) 2Al2O3 (s) ΔH° = -3351 kJ

exothermic; released

***FOR PROBLEM 23-30 use DIAGRAM The substance in this diagram is being

heated

2. Which one of the following is an endothermic process?

ice melting boiling soup BOTH

3. A __________ ΔH corresponds to an __________ process

negative; exothermic

12. When gaseous water condenses to form liquid water,

only potential energy changes

4. ΔH for an endothermic process is _____ while ΔH for an exothermic process is _______.

positive; negative

17. The heat of fusion is defined as the energy required at constant temperature to change 1 unit mass of a

solid to a liquid