Unit 6 – Chemistry Test

1. Two samples of iron, one with a mass of 50g and the other with a mass of 500g were placed in a boiling water bath at 1000C and were allowed to reach thermal equilibrium. What statement is true?a. The 50g piece has a higher temp.b. The 500g piece can transfer more heatc. The 500g piece has a higher temp.d. The 50g piece can transfer more heat

2. When your body is warmed from the effect of a electric blanker during the winter, this process is said to be (your body is the system)a. exothermicb. polythermicc. endothermicd. isothermic

3. When a sugar cube is dissolved in a cup of tea, entropy isa. decreasingb. increasing and decreasingc. at equilibriumd. increasing

4. Which of the following systems has the lowest entropya. salt dissolved in a container of waterb. sand mixed in a container of waterc. oil floating in a container of waterd. a container of frozen water

5. A reaction is spontaneous if G isa. greater than Hb. positivec. negatived. zero

6. Calculate the energy required to produce 7.0 mol Cl2O7 on the basis of the following balanced equation2Cl2(g) + 7O2(g) + 130 Cal

a. 460 Calb. 65 Calc. 19 Cald. 910 Cal

7. In an endothermic reaction, the total energy at the beginning of the reaction isa. equal to the total energy at the end of the reactionb. greater than the total energy at the end of the reactionc. less than the total energy at the end of the reactiond. None of the above

8. Two factors that determine whether a reaction will occur spontaneously are the change in the energy of a reaction system anda. the randomness of the particles in the systemb. the pressure of the systemc. the quickness of the reaction

d. the concentration of the reactants in the system

9. Which of the following best describes energy in the form of heata. the energy transferred between samples of matter because of a difference in their temperatureb. a measure of the average kinetic energy of the particles in a sample of matterc. the energy stored in a sample of matter than can be emitted during combustion reactiond. bond energy

10. Given the equation I2(s) + 62.4 kJ I2(g), which of the following is truea. H = + 62.4 kJb. The reaction releases heatc. H = - 62.4 kJd. The reaction is exothermal

11. If the enthalpy involved in a chemical reaction has a negative signa. heat is gained from the surroundingsb. no heat is involved in the reactionc. heat is neither gained nor lostd. heat is lost to its surroundings

12. What is the enthalpy change, H for the following reaction2Mg(s) + SiCl4(l) Si(s) + 2MgCl2(s)

USE THE FOLLOWINGSi(s) + 2CL2(g) SiCl4(l) H = -687 kJMg(s) + CL2(g) MgCL2 H = -641 kJ

a. -595 kJb. -1328 kJc. 46 kJd. -1969 kJ

13. Standard conditions of temperature and pressure for a thermochemical equation area. 0oC & 101 KPab. 0oC & O KPac. 25oC & 101 KPad. 25oC & 22.4 KPa

14. Free energy change depends ona. change of enthalpy onlyb. temperature onlyc. temperate and changes of entropy and enthalpyd. change of entropy only

15. As a general rule, the entropy of a solid isa. more than that of a liquidb. zeroc. more than that of a gasd. less than that of a liquid

16. In a calorimeter, the energy content of a substance is calculated from measurement of the temperature change in a known mass ofa. ironb. air

c. waterd. steel

17. Suppose reaction A has a H of -200 kJ and reaction B has a H of -100 kJ. If reaction can be written as the sum of reaction A forward and reaction B reversed, what is H for reaction C?a. +100 kJb. +300 kJc. -300 kJd. -100 kJ

18. The majority of spontaneous chemical reaction in nature area. exothermicb. free energy reactionc. positive enthalpic reactiond. endothermic

19. The standard enthalpy of formation for an element in its natural form is equal toa. its molar massb. the standard entropy minus the temperaturec. its enthalpy of fusiond. zero kilojoules per mole

20. The amount of heat transferred from an object depends on which of the followinga. mass of the objectb. initial temperature of the objectc. specific heat of the objectd. all of the above

21. In the reaction below, entropy is 2H2(g) + O2(g) 2H2O(g)a. at equilibriumb. increasingc. equal to the enthalpyd. decreasing

22. In an exothermic reaction, the energy stored in the chemical bonds of the reactants isa. less than the heat releasedb. equal to the energy stored in the bonds of the productsc. less than the energy stored in the bond of the productsd. greater than the energy stored in the bonds of the products

23. Two objects are sitting next to each other in direct sunlight. Object A gets hotter than Object B. Choose the correct statement from the choices belowa. Can’t tell from the given informationb. Object A has a lower specific heat capacity than Object Bc. Both objects have the same specific heat capacityd. Object A has a higher specific heat capacity than Object B

24. What would likely happen if you were to touch a flask in which an endothermic reaction were occurringa. the flask would feel the same as before reaction startedb. the flask would feel warmer than before reaction startedc. the flask would feel cooler than before reaction started

d. None of the above

25. How does a calorie compare to a joulea. calorie is larger than a jouleb. calorie is smaller than a joulec. relationship can’t be determinedd. calorie is equal to a joule

26. If there are 4.187 J per calorie, what would be the equal of 15 caloriesa. 6300 Jb. 63 Jc. 63 kJd. 3600 J

27. The heart required to change one mole of a substance from a solid to a liquid is called thea. Hvap

b. Hcont

c. Hfus

d. Hsolid

28. Based on the chart of specific heat capacities, which element would require the most heat to raise one gram of a substance 10C?a. silverb. ironc. leadd. mercury

29. The vaporization of a substance is a(n) _________________ processa. polythermicb. exothermicc. ectothermicd. endothermic

30. Spontaneous reactions are driven bya. increasing enthalpy and increasing entropyb. decreasing enthalpy and increasing entropyc. increasing enthalpy and decreasing entropyd. decreasing enthalpy and decreasing entropy

FREE RESPONSE

31. A 135.0 g piece of gold initially at a temperature of 2820C is placed in 125 mL of water in a coffee cup calorimeter originally at a temperature of 24.50C. What is the final temperature of the water?

32. Determine how many kilojoules of heat are given off when 122.6 g of sodium iodide, NaI, is produced.

33. Using the standard heat of formations provided on the reference sheet, calculate the standard heat of reaction ( Hrxn) for the following: 2SO2(g) + O2(g) 2503(g).

34. How much energy (in kJ) would be needed to heat 500.0 g of water from 350C to 1500C?

35. Mercury has a density of 13.534 g/cm3. How much heat is required to change from 22.75 cm3 of mercury from 240C to 980C.

36. Nitrogen dioxide can combine to form dinitrogen tetroxide according to the following:2NO2(g) N2O4(g) H = -57.2 kJ. If the change in entropy is -175.9 J/K, under what

temperature conditions is this reaction spontaneous.

ANSWER KEY

Question # Correct Answer1 B2 C3 D4 D5 C6 A7 C8 A9 A10 A11 D12 A13 C14 C15 D16 C17 D18 A19 D20 D21 ??22 D23 B24 C25 A26 C27 C28 B29 D30 B