Formula of Hydrocarbons, Alkenes & Alkynes

Formulas of Hydrocarbons
Alkenes
They are also known as olefins.
They are unsaturated hydrocarbons.
They have a general formula of
CnH2n, n = 2, 3, 4, …�
C2H4, C3H6, C4H8, C5H10 ….. Homologous
series of alkenes.
Their functional group is – C = C –.
For example if n is 3, then the formula of
the alkene becomes:
C3H2×3 = C3H6.�
Generally alkenes have the following
physical state.
1. C2 - C4 => exist in gaseous state.
2. C5 - C17 => occur in liquid state.
3. C18 and above are found in solid state�
Alkynes
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They are unsaturated hydrocarbons.
They have a general formula of
CnH2n-2, where n = 2, 3, 4, … .
C2H2, C3H4, C4H6, C5H8 ……..
Homologous series of alkynes.
Their functional group is –C=_ C –.
�For example if n is 3, then the formula
of the alkyne becomes:
C3H2×3-2 = C3H4.
Generally alkynes have the following
physical state.
1. Ethyne, propyne and butyne are gases.
2. C5 - C17 => exist in liquid state.
3. C18 and above are found in solid state.
�Nomenclature of Hydrocarbons
The name of the alkenes end with
the suffix ‘-ene’.�

1. CHEMISTRY GRADE 8 UNIT ONE CLASSIFICATION OF COMPOUNDS (Continued)

2. 1 . 2 . 1 Formulas of H ydrocarbons ( Co nt ' d ) Alkenes They are also known as olefins.
They are unsaturated hydrocarbons.
They have a general formula of C n H 2n , where n = 2, 3, 4 , …

3. Alkenes ( Co nt ' d ) C 2 H 4 , C 3 H 6 , C 4 H 8 , C 5 H 10 ….. Homologous series of alk e nes. Their functional group is – C = C – . For example if n is 3 , the n the formula of the alk e ne becomes: C 3 H 2 × 3 = C 3 H 6 .

4. Alkenes ( Co nt ' d ) Generally alk e nes have the following physical state. 1. C 2 - C 4 => exist in gas eous state . 2. C 5 - C 1 7 => occur in liquid state . 3. C 1 8 and above are found in solid stat e .

5. Alkynes They are unsaturated hydrocarbons . They have a general formula of C n H 2n - 2 , where n = 2, 3, 4 , … .

6. Alkynes ( Co nt ' d ) C 2 H 2 , C 3 H 4 , C 4 H 6 , C 5 H 8 …….. Homologous series of alkynes. Their functional group is – C C – . For example if n is 3 , the n the formula of the alk y ne becomes: C 3 H 2 × 3 - 2 = C 3 H 4 . I I I

7. Generally alk y nes have the following physical state. 1. Ethyne , propyne and butyne are gas e s . 2. C 5 - C 1 7 => exist in liquid state . 3. C 1 8 and above are found in solid stat e . Alkynes ( Co nt ' d )

8. Exercise Write the formula of alk e ne and alkyne that contain three, five, seven, eight and ten carbon atoms , respectively . Give the formula for the alk e ne and alkyne homologues immediately coming before and after C 7 H 16 , r espectively . A compound has seven carbon atoms that belongs to alk y nes. What would be the formula of the compound? What is the formula of the simplest member of alk e nes and alkyne , respectively ?

9. 1 . 2 . 2 Nomenclature ( Naming ) of Hydrocarbons Nomenclature of hydrocarbons refers to naming of hydrocarbons.
To name hydrocarbons use the following prefixes. Prefix Number of carbon atoms Meth - 1 Eth - 2
Prop - 3
But - 4 P ent - 5

10. Nomenclature of Hydrocarbons ( Co nt ' d ) Prefix Number of carbon atoms H ex - 6 H ept - 7 O ct - 8 N on - 9 D ec- 10

11. Nomenclature of Hydrocarbons ( Co nt ' d ) Example Formula of alkane Name CH 4 Methane C 2 H 6 Ethane C 3 H 8 Propane C 4 H 10 Butane The name of the alkanes end with the suffix ‘ -ane ’ .

12. Example Formula of alkene Name C 2 H 4 Eth e ne
C 3 H 6 Prop e ne C 4 H 8 But e ne Nomenclature of Hydrocarbons ( Co nt ' d ) The name of the alk e nes end with the suffix ‘ - e ne ’ .

13. Nomenclature of Hydrocarbons ( Co nt ' d ) Example Formula of alkyne Name C2H2 Ethyne
C3H4 Propyne
C4H6 Butyne The name of the alkynes end with the suffix ‘ -yne ’

14. Home Work Exercise1.3 page -5

15. 1 . 2 . 3 Importance O f Organic Compounds Many organic compounds are very useful in our daily life . Importance of Some Hydrocarbons Methane ( CH 4 ) Methane is mainly used as a source of energy for cooking , heating and generating electricity . Biogas that is used as a domestic fuel mainly consists of methane .

16. Importance of Some Hydrocarbons ( C o nt ' d ) Propane and Butane Both propane and butane are gaseous alkanes . The mixture of propane and butane is stored in steel cylinder . It is marked as bottled gas and commonly know as " butagas " . It is mainly used for cooking and heating .

17. Importance of Some Hydrocarbons ( C o nt ' d ) Octan e octane is a liquid alkane and one components of petrol . It is used as fuel in engines . D ecane Decane is one of components of kerosene . Kerosene is used for lighting and cooking . It is used as jet fuel .

18. Importance of Some Hydrocarbons ( C o nt ' d ) E the ne and Propene Ethene and propene are gaseou alkenes . Both ethene and propene are used for production of plastics . Ethene is used for production of polyethylene plastics . Propene is used for production of poly prop ylene plastics .

19. Importance of Some Hydrocarbons ( C o nt ' d ) Ethyne Ethyne is the simplest alkyne . One of the main uses of e thyne is to produce oxy- acetylene flame , which is used in the cutting and welding of steel and iron .

20. 1 . 2 . 3 Importance O f Other Organic Compounds Ethanol ( Ethyl alcohol ) , C 2 H 5 OH All alcohol ic beverages contain ethanol . For example ' Tella ' , ' Tej ' , ' Katikalla ' , ' Wine ' , ' Ouzo ' , etc . Ethanol mixed with petrol and used as a fuel . It is also used in production of acetic acid , and in hospital s and clinics for cleaning wound .

21. 1 . 2 . 3 Importance O f Other Organic Compounds Ethanoic Acid ( Acetic acid ) When we eat uncooked vegetables such as salad , we add ' acheto ' or vinegar . Vinegar is used as food flavor ing agent . I t is also used as disinfectant . For table vinegar , the concentration of acetic acid ranges from 4 % to 8 % . For use in preserv ing vegetables ( pickling ) it ranges up to 1 8 % .

22. 1 . 2 . 3 Importance O f Other Organic Compounds Formalin The water solution of formaldehyde is referred to as formalin . Formal in contain s 4 % of formaldehyde . Formaline is used for preservation of biological sp e ci mens , because it makes proteins hard and insoluble .

23. Home Work Exercise1. 5 ( page - 6 ) & Exercise 1 . 6 ( page 9 - 1 ) (To be Continued )

24. 1 . 3 Inorganic Compounds Inorganic compounds are non carbon containing compounds . They are also called mineral compounds because they are the major constituents of rocks and minerals .

25. Classification of inorganic compounds Inorganic Compounds Oxides Acids Bases Salts

26. A . Oxides Oxides are binary compounds containing oxygen . N oble gases ( He , Ne , Ar , Kr , . . . ) and inactive metals such as gold, platinum, palladium d o not react with oxygen t o form oxides. Oxides are combination of elements with oxygen .

27. A . Oxides ( Cont'd ) + Elements O xygen Oxides

28. Example s Of Oxides Examples of oxides are : Lithium oxide ( Li 2 O ) , sodium oxide ( Na 2 O ) , nitrogen oxides ( N O 2 , N 2 O , NO , N 2 O 5 , . . . ) , sulphur trioxide ( SO 3 ) , carbon oxides ( CO & CO 2 ) , magnesium oxide ( MgO ) , water ( H 2 O ) , calcium oxide ( CaO ) , Iron oxides ( Fe 2 O 3 & FeO ) , etc .

29. A . Oxides ( Cont'd ) Types of oxides D e p e n d i n g on their elemental composition m ost oxides are classified as : Metallic Oxides and Non metallic Oxides .

30. Types of oxides Metallic Oxides Metallic oxides containing metal and oxygen . Example : CaO , Na 2 O , Al 2 O 3 , MgO , etc . Metallic Metallic Elements Oxides + Oxygen

31. 2 . Non m etallic Oxides N o n m etallic oxides containing non metal and oxygen . Examples : NO 2 , H 2 O , CO 2 , CO , SO 2 , P 2 O 5 , etc. Types of oxides ( Cont'd ) N o n m etallic N o n m etallic Elements Oxides + Oxygen

32. Types of oxides ( Cont'd ) Based on chemical properties oxides are further classified a s : Acidic oxide 4 . Neutral oxide Basic oxide 5 . Peroxide Amphoteric oxide

33. 1 . Acidic oxides They are oxides that form acidic solution when dissolved in water. Most non – metallic oxides are acidic oxides . Example SO 2 – sulphur dioxide SO 3 – sulphur trioxide CO 2 – carbon dioxide NO 2 – nitrogen dioxide

34. 1 . Acidic oxides ( Co nt 'd ) N 2 O 3 – Dinitrogentrioxide N 2 O 5 – Dinitrogenpentoxide P 2 O 5 – P osphorus pentoxide Few metallic oxides are acidic oxides CrO 3 – C hromium (VI) oxide WO 3 – Tungsten oxide Mn 2 O 7 – M anganese (VII) oxide

35. 1 . Acidic oxides ( Co nt 'd ) All oxides of metalloids are acidic oxides B 2 O 3 – boron oxide SiO 2 – silicon dioxide GeO 2 – germanium oxide

36. 2 . Basic oxides They are oxides that react with water and form bases . Some examples of basic oxides are: Li 2 O – Lithium oxide Na 2 O – sodium oxide All basic oxides are metallic oxides but all metallic oxides are not necessarily basic oxides .

37. S ome E x amples of B asic O xides ( Co nt' d ) CaO – Calcium oxide SrO – Strontium oxide BaO – Barium oxide CuO Copper (II) oxide Fe 2 O 3 – Iron (III) oxide K 2 O – Potassium oxide MgO – Magnesium oxide

38. 3 . Amphoteric oxides These are oxides that have both acidic and basic properties. Example Al 2 O 3 – aluminum oxide Z nO – zinc oxide SnO – Tin (II) oxide SnO 2 – Tin (IV) oxide PbO 2 – lead (IV) oxide

39. 3 . Amphoteric oxides ( Co nt' d ) Example ZnO + 2 HCl -------- > ZnCl 2 + 3 H 2 O ZnO + 2 NaOH ------- > Na 2 ZnO 2 + H 2 O ( Sodium zinicate ) Amphoteric oxides act as acid when they react with basic and as base when they react with acid.

40. 4 . Neutral oxides These are oxides that do not react with acids and bases. E xample H 2 O – water CO – carbon monoxide N 2 O – Nitrous oxide (laughing gas) NO – Nitric oxide

41. 5 . Peroxides These are oxides that contain oxygen to oxygen linkage ( - O - O - ) . Are oxides that react with cold dilute acids to form hydrogen peroxide . Peroxide + Acid -------- > S alt + H ydrogen peroxide

42. 5 . Peroxides ( Co nt 'd ) Example H 2 O 2 – hydrogen peroxide Na 2 O 2 – sodium peroxide K 2 O 2 – potassium peroxide CaO 2 – calcium peroxide SrO 2 strontium peroxide BaO 2 - Barium peroxide

43. Properties of Oxides An acidic oxide react with water , to form an acid . Example C O 2 + H 2 O ------------- > H 2 CO 3 SO 3 + H 2 O --------- ‐ ---- > H 2 SO 4 Acidic oxide + water ------------ > Acid

44. Properties of Oxides ( Co nt 'd ) 2 . Acidic oxides react with bases to form salts and water . Example SO 3 + Ca ( OH ) 2 ------- > CaSO 4 + H 2 O Acidic oxide + Base - -------- > Salt + Water

45. Properties of Oxides ( Co nt 'd ) 3 . A basic oxide or basic an h y d r i d e react with water to produce a base . Example CaO + H 2 O --- - - - - ----- > Ca ( OH ) 2 K 2 O + H 2 O - ------------ > 2 KOH Basic Oxide + Water ---------- > Base

46. Properties of Oxides ( Co nt 'd ) 4 . Basic oxides react with acids to form salts and water . Example CaO + 2 HCl --------- > CaCl 2 + H 2 O Basic Oxide + Acid ---------- > Salt + Water

47. Properties of Oxides ( Co nt 'd ) 5 . Basic oxides react with acid ic oxide s to form salts . Example CaO + CO 2 - - - - - - - - - - - - - - > CaCO 3 3 MgO + P 2 O 5 - - - - - - - - - - > Mg 3 ( PO 4 ) 2 Basic Oxide + Acid ic Oxide ---------- > Salt

48. Preparation of oxides By direct combination of element with oxygen ( direct synthesis ) . Example: S + O 2 SO 2 (acidic oxide) 2Mg + O 2 2MgO (basic oxide) Element + Oxygen Oxide Metal + Oxygen M etallic O xide Non - metal + oxygen Non-metallic O xide

49. Preparation of oxides ( Co nt ' d ) 2 . Thermal decomposition of some compounds ( indirect synthesis ) . Example CaCO 3 CaO + CO 2 M etallic oxide A . Carbonates ----------- - - > + C arbon dioxide heat heat

50. Preparation of oxides ( Co nt ' d ) B . Decomposition of metallic nitrates by heat . Example 2 Zn(NO 3 ) 3 2 ZnO + 4 NO 2 + O 2 M etallic O xide + Metallic N itrates ----------- > N itrogen dioxide + Oxygen heat heat

51. Preparation of oxides ( Co nt ' d ) C . Thermal decomposition of metallic hydroxides Example Cu(OH) 2 CuO + H 2 O Metallic M etallic + W ater H ydroxide O xide heat heat

52. Home Work Exercise 1.10 on page 18

53. B . Acids Acids are substances that release hydrogen ion ( H+ ) when dissolved in water.
They donate hydrogen ion (proton) to other substances.
They are derived from a Latin word “acidus” meaning sour.
They are found in living and non-living matter.

54. B . Acids ( Co nt ' d ) For example:
Lemon Juice – citric acid
Our stomach – hydrochloric acid
Ant and bees – formic acid Car battery – sulphuric acid
Sour milk – lactic acid
Vinegar – acetic acid
Soft drinks and mineral water – carbonic acid

55. The PH Scale PH is the measure of acidity or alkalinity of a solution . The PH scale ranges from to 1 4 . = > Acids have PH value below 7 . The more acid ic a solution is , the lower its PH value will be . = > Base s have PH value above 7 . The more basic a solution is , the higher its PH value will be . = > The PH value of a neutral solution is very close to 7 . .

56. The PH Scale ( Co nt ' d ) Figure The PH scale Neutral 7 1 4 Acid ity increases Basi city increases

57. Preparation of Acids Two ways of preparing acids are ; Direct combination of elements and Reaction of acidic oxide s with water

58. Preparation of Acids ( Co nt ' d ) Direct Combination of Elements Non- metal + Hydrogen - - - - - - - - - - - - > Binary Compounds Binary Compounds + water - - - - - - - - > Acids Example H 2 ( g ) + Cl 2 ( g ) - - - - - - - - - - - > 2 HCl ( g ) ( Binary compou nd ) HCl ( g ) + H 2 O ( l ) - - - - - - - - > HCl ( aq ) ( Hydrochloric Acid )

59. Preparation of Acids ( Co nt ' d ) II . Reaction of Acidic Oxide s w ith Water Acidic oxide s react with water to form acids . Example s N 2 O 5 ( g ) + H 2 O ( l ) - - - - - - - - - > 2 HNO 3 ( aq ) SO 3 ( g ) + H 2 O ( l ) - - - - - - - - - - > H 2 SO 4 ( aq ) Acid anhydride + Water - - - - - - - - - - - - - > Acid

60. Acids change color of indicators . Indicators are substances used to identify whether a given substance is acidic or basic . Properties of Acids

61. Properties of Acids ( Co nt ' d ) Table : color of indicators in acidic solutions Indicator s Color in acidic solution Litmus paper red Phenophythalien colorless Methyl orange red Universal indicator yellow, orange or red

62. Properties of Acids ( Co nt ' d ) 2 . Acids react with active metal to form salt and water . Example: Mg + 2HCl - - - - - > MgCl 2 + H 2 Active Metal + Acid s Salt + Hydrogen

63. Properties of Acids ( Co nt ' d ) 3 . Reaction of acids with carbonares and hydrogen carbonates . Example CaCO 3 + 2HBr CaBr 2 + CO 2 + H 2 O KHCO 3 + HBr KBr + CO 2 + H 2 O Carbonates / Acids + Hydrogen Salt + CO 2 + H 2 O C arbonates

64. Properties of Acids ( Co nt ' d ) 4 . Acids neutralize s bases . Example HNO 3 + LiOH LiNO 3 + H 2 O
2HNO 3 + Li 2 O 2LiNO 3 + H 2 O Acid + Base Salt + W ater

65. Read different chemistry reference books to investigate and write the common uses of Hydrochloric Acid Nitric Acid and Sulphuric Acid . The paper will be submitted on January 2 , 2 2 1 . Individual Assignment ( 1 % )

66. (To be Continued )