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HYDROCARBON FUELS

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Title: HYDROCARBON FUELS


1
HYDROCARBON FUELS
  • MANY ARE ALKANES
  • ALKANES ARE HYDROCARBONS CONTAINING ONLY SINGLE
    BONDS BETWEEN CARBONS

2
  • OFTEN ARE MIXTURES OF STRAIGHT CHAIN AND BRANCHED
    CHAIN ALKANES

3
HYDROCARBONS CONTINUED
  • STRAIGHT CHAIN ALKANES ALKANES IN WHICH CARBONS
    ARE BONDED TO NO MORE THAN 2 OTHER CARBONS

4
  • BRANCHED CHAIN ALKANES AT LEAST ONE CARBON IS
    BONDED TO 3 OR 4 OTHER CARBONS

5
PREFIXES FOR ORGANIC COMPOUNDS
  • METH
  • ETH
  • PROP
  • BUT
  • PENTA
  • HEXA
  • HEPTA
  • OCTA
  • NONA
  • DECA

6
STRAIGHT CHAIN ALKANE EXAMPLES
  • CH4
  • METHANE
  • C2H6
  • ETHANE

7
  • C3H8
  • PROPANE

8
MOLECULAR FORMULAS OF ALKANES
  • GENERAL FORM IS CNH2N2 WHERE N IS THE NUMBER OF
    CARBONS

9
STRUCTURAL FORMULAS OF SC ALKANES
  • CONNECT CARBONS IN A STRAIGHT CHAIN WITH SINGLE
    BONDS

10
  • ATTACH HYDROGENS SO THAT EVERY CARBON HAS 4 BONDS
    IN TOTAL

11
INTERMOLECULAR ATTRACTION FORCES
  • CAUSED BY OPPOSITE CHARGES IN ATOMS
  • AFFECTED BY UNEQUAL SHARING OF ELECTRONS IN
    COVALENT BONDS

12
IM FORCES CONTINUED
  • DETERMINE PHASE, MELTING POINT, BOILING POINT,
    DENSITY, AND VISCOSITY

13
MELTING
  • SOLIDS HAVE MOLECULES CLOSE TOGETHER IN RIGID
    POSITIONS
  • TO MELT, MOLECULES MUST GAIN ENERGY AND MOVE
    APART SLIGHTLY

14
MELTING CONTINUED
  • THIS REQUIRES THEM TO OVERCOME ATTRACTION FORCES
  • SUBSTANCES WITH STRONG ATTRACTION FORCES REQUIRE
    MORE ENERGY FOR THIS TO HAPPEN

15
MELTING CONTINUED
  • MORE ENERGY MEANS THEY HAVE HIGHER MELTING POINTS
    THAN SUBSTANCES WITH WEAKER ATTRACTION FORCES

16
BOILING
  • MOLECULES MUST GAIN ENERGY AND MOVE FARTHER APART
    IN ORDER TO BOIL

17
  • SUBSTANCES WITH STRONG ATTRACTION FORCES REQUIRE
    MORE ENERGY FOR THIS TO HAPPEN

18
BOILING CONTINUED
  • WHAT AFFECT DOES THIS HAVE ON THE BOILING POINT?

19
VISCOSITY
  • VISCOSITY IS THE RESISTANCE TO FLOWING
    (THICKNESS)
  • HIGH VISCOSITY MEANS THICK (DOES NOT EASILY FLOW)

20
  • HIGH VISCOSITY IS THE RESULT OF STRONG ATTRACTION
    FORCES

21
DENSITY
  • HOW MUCH MASS IN A GIVEN SPACE
  • RELATED TO CLOSENESS OF MOLECULES
  • WHAT AFFECT DOES STRONG ATTRACTION FORCES HAVE?

22
PROPERTY DIFFERENCES OF SC ALKANES
  • AS THE MOLECULES GET LONGER, THEY ATTRACT ONE
    ANOTHER MORE
  • LONGER IS STRONGER!

23
PROPERTY DIFFERENCES
  • WHAT HAPPENS TO MP?
  • WHAT HAPPENS TO BP?
  • WHAT HAPPENS TO VISCOSITY?
  • WHAT HAPPENS TO DENSITY?

24
ISOMERS
  • COMPOUNDS HAVING THE SAME MOLECULAR FORMULA BUT
    DIFFERENT STRUCTURAL FORMULAS
  • EXAMPLE BUTANE AND METHYLPROPANE

25
ISOMERS CONTINUED
  • METHANE, ETHANE, AND PROPANE HAVE NO ISOMERS
  • ALL OTHER ALKANES HAVE AT LEAST ONE ISOMER

26
  • FUELS ARE OFTEN MIXTURES OF ISOMERS

27
PROPERTY DIFFERENCES OF ISOMERS
  • BRANCHING KEEPS THE MOLECULES FROM BEING AS CLOSE
    TOGETHER AS STRAIGHT MOLECULES
  • THIS CAUSES WEAKER INTERMOLECULAR FORCES

28
PROPERTY DIFFS CONTINUED
  • HAVE DIFFERENT BOILING POINTS, MELTING POINTS,
    DENSITIES, AND VISCOSITIES THAN STRAIGHT CHAIN
    ISOMERS

29
  • MORE BRANCHING HAS A GREATER EFFECT

30
EXAMPLE EFFECTS
  • C5H12
  • PENTANE BP IS 36.1 ?C
  • 2 METHYL BUTANE BP IS 27.8 ?C
  • 2 DIMETHYL PROPANE BP IS 9.5 ?C

31
PROPERTY DIFFS CONTINUED
  • WHAT EFFECT DOES BRANCHING HAVE ON MP?
  • DENSITY?
  • VISCOSITY?

32
PETROLEUM
  • ALSO CALLED CRUDE OIL
  • LIQUID FOSSIL FUEL (MADE FROM DECOMPOSING ORGANIC
    MATTER)

33
  • MIXTURE OF HYDROCARBONS, NITROGEN, SULFUR,
    OXYGEN, AND SOME METAL COMPOUNDS

34
DISTILLATION
  • PROCESS OF SEPARATING LIQUIDS WITH DIFFERENT
    BOILING POINTS

35
  • FRACTIONAL DISTILLATION SEPARATES MIXTURES INTO
    MANY PARTS BASED ON BP
  • SEE PAGE 174

36
DISTILLATION CONTINUED
  • PRODUCTS ARE A MIXTURE OF VARIOUS HYDROCARBONS
  • PETROCHEMICAL SUBSTANCE MADE FROM PETROLEUM

37
CRACKING
  • BREAKING LONG CHAIN MOLECULES INTO SHORTER ONES
    (C1 TO C14)

38
  • INVOLVES A CATALYST A SUBSTANCE THAT SPEEDS UP
    A REACTION W/O BEING CONSUMED ITSELF

39
GASOLINE
  • HEXANE, HEPTANE, AND OCTANE TOO BURN RAPIDLY AND
    CAUSE ENGINE KNOCK (IGNITING TOO SOON)

40
  • BRANCHED CHAIN ALKANES ARE BETTER FUELS SINCE
    THEY DONT KNOCK AS MUCH

41
GASOLINE CONTINUED
  • 2,2,4 TRIMETHYLPENTANE (AN ISOMER OF OCTANE) IS
    THE BEST FUEL FOR CAR ENGINES BECAUSE IT DOES NOT
    KNOCK AS MUCH

42
  • ALSO CALLED ISOOCTANE

43
OCTANE NUMBER
  • RATING SHOWING HOW A FUEL COMPARES TO THE
    CHARACTERISTICS OF ISOOCTANE
  • HEPTANE ASSIGNED A RATING OF ZERO (IT IS A VERY
    POOR FUEL)

44
OCTANE CONTINUED
  • EXAMPLE 87 MEANS THE FUEL HAS THE SAME KNOCKING
    AS 87 ISOOCTANE AND 13 HEPTANE

45
  • 100 IS PURE ISOOCTANE (NOT THE HIGHEST NUMBER)

46
FUEL ADDITIVES
  • ADDED TO IMPROVE OCTANE RATING
  • TETRAETHYL LEAD (C2H5)4Pb SLOWS THE BURNING OF
    ALKANES AND REDUCES KNOCK AND ADDED 3 POINTS TO
    THE OCTANE RATING

47
FUEL ADDITIVES CONT.
  • LEAD BASED ADDITIVES NO LONGER USED DUE TO
    ENVIRONMENTAL POLLUTION

48
OXYGENATED FUELS
  • BLENDED WITH GAS TO ADD OXYGEN WHICH IMPROVES
    OCTANE RATING AND REDUCES CARBON MONOXIDE OZONE

49
  • EXAMPLES METHANOL, ETHANOL, AND MTBE (METHYL
    TERT BUTYL ETHER)

50
OXYGENATED FUELS CONTINUED
  • ARE VOCs
  • ALSO CALLED REFORMULATED GASOLINE
  • REQUIRED IN POLLUTED AREAS

51
  • MTBE HAS BEEN FOUND IN DRINKING WATER EFFECTS
    UNKNOWN

52
CHEMICAL REACTIONS
  • SUBSTANCES THAT GO INTO THE REACTION ARE CALLED
    REACTANTS
  • SUBSTANCES MADE FROM THE REACTION ARE CALLED
    PRODUCTS

53
CHEMICAL EQUATIONS
  • DESCRIBE REACTIONS
  • MUST BE BALANCED (NUMBERS OF ATOMS MUST BE THE
    SAME ON BOTH SIDES) BECAUSE OF THE LAW OF
    CONSERVATION OF MATTER

54
CHEMICAL EQUATIONS CONTINUED
  • COEFFICIENTS SHOW HOW MANY MOLECULES ARE
    INVOLVED IN A REACTION

55
BALANCING EQUATION
  • CHANGE COEFFICIENTS (NOT SUBSCRIPTS) SO THAT
    NUMBERS OF EACH ELEMENT ARE EQUAL ON BOTH SIDES

56
EXAMPLE 1
  • H2 O2 ? H2O
  • 2H2 1O2 ? 2H2O

57
EXAMPLE 2
  • Na Cl2 ? NaCl
  • 2Na 1Cl2 ? 2NaCl

58
EXAMPLE 3
  • CH4 O2 ? CO2 H2O
  • 1CH4 2O2 ? 1CO2 2H2O

59
COMBUSTION OF HYDROCARBONS
  • RAPID EXOTHERMIC REACTION WITH OXYGEN
  • ALSO CALLED BURNING
  • PRODUCTS OF COMPLETE COMBUSTION ARE CO2 AND H2O

60
EXAMPLE COMBUSTION REACTION FOR WAX
  • 1C25H52 38O2 ? 25CO2 26H2O

61
INCOMPLETE COMBUSTION
  • CAUSED BY INSUFFICIENT OXYGEN
  • PRODUCTS INCLUDE SOME CARBON MONOXIDE AND CARBON
    (SOOT)

62
CATALYTIC CONVERTERS
  • HIGH TEMPERATURE ENCOURAGES COMPLETE BURNING TO
    REDUCE CO AND CARBON EMISSIONS IN EXHAUST

63
HEAT OF COMBUSTION
  • THE ENERGY GIVEN OFF BY BURNING IS CALLED THE
    HEAT OF COMBUSTION
  • AMOUNT OF HEAT VARIES WITH FUEL

64
  • EXPRESSED IN KILOJOULES PER GRAM

65
HEAT OF COMBUSTION CONTINUTED
  • hC ENERGY PRODUCED / MASS BURNED
  • METHANE IS 55. 6 kJ/g
  • PROPANE IS 50.0 kJ/g
  • BUTANE IS 49.3 kJ/g

66
  • OCTANE IS 47. 8 kJ/g
  • PREDICTION FOR DECANE?

67
OXIDATION
  • ANY REACTION IN WHICH A SUBSTANCE LOSES ELECTRONS
  • IRON LOSES ELECTRONS TO OXYGEN DURING RUSTING

68
REDUCTION
  • ANY REACTION IN WHICH A SUBSTANCE GAINS ELECTRONS
  • OXYGEN GAINS ELECTRONS FROM IRON DURING RUSTING

69
EXAMPLE REACTION
  • Zn O ? Zn2 O-2
  • ZINC LOSES 2 ELECTRONS AND IS OXIDIZED
  • OXYGEN GAINS 2 ELECTRONS AND IS REDUCED

70
HALF REACTIONS
  • SHOW THE OXIDATION OR REDUCTION SEPARATE FROM THE
    OTHER
  • Zn ? Zn2 2e-
  • O 2e- ? O-2

71
OXIDATION-REDUCTION REACTION
  • CALLED A REDOX REACTION
  • ALSO CALLED A GALVANIC PROCESS

72
OXIDATION CONTINUED
  • MAKES ELECTRONS AVAILABLE
  • THE RELEASED ELECTRONS FLOW TO FORM A CURRENT

73
OXIDATION CONTINUED
  • THE AMOUNT OF CURRENT IS RELATED TO HOW STRONGLY
    ATOMS HOLD VALENCE e-
  • DIFFERENT FOR EACH ELEMENT

74
OX CONTINUED
  • ELECTRONS WILL FLOW FROM AN ELEMENT THAT GIVES
    THEM UP EASILY TO ONE THAT DOES NOT GIVE THEM UP
    EASILY
  • THIS CAUSES AN ELECTRIC CURRENT

75
POTENTIAL DIFFERENCE
  • FORCE PUSHING ELECTRONS IN A CURRENT
  • CALLED VOLTAGE

76
GALVANIC CELL
  • A DEVICE CONTAINING SUBSTANCES THAT UNDERGO AN
    REDOX REACTION AND PRODUCE A VOLTAGE

77
  • ALSO CALLED VOLTAIC CELL

78
GALVANIC CELL CONTINUED
  • SUBSTANCES ARE SEPARATED
  • REACTION TAKES PLACE WHEN THE SUBSTANCES ARE
    CONNECTED WITH A CONDUCTOR

79
PARTS OF A CELL
  • CATHODE IS THE PLACE WHERE REDUCTION OCCURS
    (ELECTRONS FLOW TO IT)
  • CATHODE IS POSITIVE

80
PARTS OF A CELL CONT.
  • ANODE IS THE PLACE WHERE OXIDATION OCCURS
    (ELECTRONS FLOW FROM IT)
  • IT IS NEGATIVE

81
  • ELECTROLYTE SUBSTANCE THAT ALLOWS IONS TO MOVE
    IN THE CELL

82
BATTERY
  • A SERIES OF GALVANIC CELLS (SOME ARE ONLY 1 CELL)
  • DRY CELLS USE MOIST ELECTROLYTES RATHER THAN
    LIQUID ONES

83
CARBON DRY CELL
  • GRAPHITE ROD SURROUNDED BY MOIST MnO2 CARBON
    PASTE IS THE CATHODE
  • ZINC ANODE (CASE)
  • MOIST NH4Cl AND ZnCl2 ELECTROLYTE

84
DRY CELL CONTINUED
  • Mn IS REDUCED
  • REACTION PRODUCES AMMONIA GAS THAT CAUSES BATTERY
    TO EXPAND
  • ELECTROLYTE IS ACIDIC

85
ALKALINE DRY CELL
  • CATHODE IS A MOIST PASTE OF MnO2 AND GRAPHITE
  • ANODE IS MOIST PASTE OF ZINC AND KOH AROUND A
    BRASS COLLECTOR

86
ALKALINE VS. CARBON
  • HAS LONGER SHELF LIFE THAN CARBON DRY CELL
  • LESS ACIDIC
  • NO AMMONIA GAS
  • MORE RELIABLE OPERATING LIFE

87
LEAD STORAGE BATTERY
  • ANODE IS LEAD METAL
  • CATHODE IS PbO2
  • ANODE IS OXIDIZED TO Pb2
  • CATHODE IS REDUCED FROM Pb4 TO Pb2

88
LEAD STORAGE CONTINUED
  • Pb2 COMBINES WITH SO4-2 FROM SULFURIC ACID
    ELECTROLYTE TO FORM PbSO4

89
  • APPLYING A VOLTAGE TO THIS BATTERY CAUSES PbSO4
    TO REACT WITH WATER TO FORM PbO2 AND Pb

90
NICKEL-CADMIUM BATTERY
  • ANODE IS CADMIUM
  • CATHODE IS NiO2
  • ELECTROLYTE IS KOH SOLUTION

91
CORROSION
  • A NATURAL GALVANIC PROCESS (REDOX REACTION)
  • OCCURS WHEREVER ACTIVE METALS ARE IN CONTACT WITH
    SUBSTANCES THAT CAN OXIDIZE THEM

92
RUST
  • OXIDATION OF IRON BY OXYGEN IN THE PRESENCE OF
    WATER
  • WATER IS THE ELECTROLYTE
  • ANODIC RXN Fe ? Fe2 2e-

93
  • MANY CATHODIC REACTIONS

94
RUST CONTINUED
  • OVERALL 2Fe 3O2 ? 2Fe2O3

95
CORROSION INHIBITORS
  • SUBSTANCES THAT SLOW THE RATE OF ELECTRON
    TRANSFER FROM THE OXIDIZED SUBSTANCE
  • ADDED TO CAR COOLING SYSTEM STICK TO IRON
    SURFACE

96
INHIBITORS CONTINUED
  • EXAMPLES CERTAIN PHOSPHATES, CHROMATES, AND
    ORGANIC COMPOUNDS
  • PAINT CONTAINING RED LEAD (Pb3O4) OR ZINC
    CHROMATE (ZnCrO4) WORK WELL

97
CATHODIC PROTECTION
  • PUT A MORE ACTIVE METAL IN CONTACT WITH METAL TO
    BE PROTECTED
  • ZINC OR MAGNESIUM IS OFTEN USED

98
  • THEY OXIDIZE INSTEAD OF THE PROTECTED METAL

99
GALVANIZED IRON
  • COATED WITH A ZINC COMPOUND TO PROVIDE CATHODIC
    PROTECTION
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