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Units Calculations Energy Vocab Temperature.

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Presentation on theme: "Units Calculations Energy Vocab Temperature."— Presentation transcript:

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4 Units

5 Calculations

6 Energy

7 Vocab

8 Temperature

9 Grab Bag

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11 What is the SI unit for temperature?

12 Kelvin

13 What is the unit for molar heat capacity?

14 J/K∙mol

15 What is the unit for n?

16 mol

17 What is the unit of energy? Write the word and symbol on the board.

18 Joules, J

19 What is the unit for molar enthalpy?

20 J/mol

21 What is the generic equation for changing Celsius into Kelvin.

22 ° C + 273= K

23 Use this equation if you are finding the change in heat for 25g of water.

24 q =nC∆T

25 Use this equation if you are finding the molar enthalpy change and do not have the amount in moles.

26 ∆ H=C∆T

27 What is the generic equation for finding the change in enthalpy for a reaction using Enthalpies of Formation?

28 ∆H= ∆H° f products- ∆H° f reactants

29 Calculate the change in enthalpy when forming aluminum oxide. 2Al(s) + 3H 2 O(l)→ Al 2 O 3 (s) + 3H 2 (g) ∆H f H2O = -285.8 kJ/mol ∆H f Al2O3 = -1676.0 kJ/mol

30 -1676.0- (3x-285.8)= -818.6kJ/mol

31 If the energy change in a reaction is negative the reaction is __________.

32 Exothermic

33 When ∆H is positive, the reaction is __________.

34 Endothermic

35 What is the only way we measure energy?

36 With a thermometer

37 Calculate the molar enthalpy change of N 2 (g) when it is heated from 90.0°C to 100.°C. The molar heat capacity of nitrogen is 29.1 J/K∙mol. Don’t forget to round to the correct sig figs.

38 291 J/mol

39 Calculate ∆H for this reaction: 3Fe 2 O 3 (s) → 6Fe(s) + 4.5O 2 (s) 3Fe 2 O 3 (s)→2Fe 3 O 4 (s) + 1/2O 2 (s) ∆H=-316kJ/mol 3Fe(s) + 2O 2 (g) → Fe 3 O 4 (s) ∆H=-201kJ/mol.

40 86kJ/mol

41 Define molar heat capacity. Hint: think about the units

42 The amount of energy required to raise 1 mole of a substance 1K.

43 Define extensive property.

44 A property that depends on the amount of substance, like heat.

45 Define intensive property. Is heat or temperature intensive?

46 A property that is independent of the amount of substance, like temperature.

47 Define heat.

48 The energy transferred between two objects of different temperatures.

49 Define Hess’s Law.

50 The change in enthalpy for a reaction is equal to the sum of the individual enthalpy changes.

51 Define temperature.

52 The average kinetic energy of the particles in an object.

53 Convert 17°C to Kelvin.

54 17°C + 273= 315K

55 Correctly write the standard thermodynamic temperature in Celsius and Kelvin on the board. This is the temp that the reactants are at for all heat measurements

56 25°C and 298K (no degree symbol for K)

57 What is ∆T in Kelvin if an object is cooled from 50°C to 30°C.

58 20K

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60 What is the generic equation when solving for ∆T in this equation: q=nC∆T?

61 ∆T = q/nC

62 Write the symbol(s) for “the change in temperature” on the board.

63 ∆T

64 How many sig figs does the following measurements have? a. 4500J b. 350.J c. 111.0J

65 a. 4500J= 2 b. 350.J = 3 c. 111.0J = 4

66 What do all the variables in q=nC∆T represent?

67 q= heat n= moles C= molar heat capacity ∆T = temperature

68 This chapter is about Thermodynamics, it is the study of _______ changes.

69 energy

70 Explain why a balloon with 50mL of water in it won’t pop when a flame is held to it.

71 Because the molar heat capacity of water is high (which means it takes a lot of energy to heat water). and the energy from the flame is transferred to the water before the balloon.

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