Organic Chemistry Part 1.2

Question 1

Why are alkanes saturated hydrocarbons?

Answer 1

Single covalent bond between carbon-carbon atoms

Question 2

General Formula of Alkanes

Answer 2

CnH2n+2

Question 3

Name the following alkyl groups(side chains)

CH3
C2H5
C3H7
C4H9
F
Cl
Br
I

Answer 3

methyl
ethyl
propyl
butyl
fluoro
chloro
bromo
iodo

Question 4

What is a structural isomer

Answer 4

same molecular formula but different structural formulae

Question 5

Isomers have same physical properties such as melting and boiling points (T/F)

Answer 5

False

Question 6

Physical Properties of Alkanes (solubility)

Answer 6

Insoluble in water
soluble in organic solvents

Question 7

Physical Property of Alkanes (boiling and melting points) and why

Answer 7

Higher relative molecular mass, higher melting and boiling points. More energy is required to overcome stronger intermolecular forces of attraction between larger alkane molecules

Question 8

Physical Property of Alkanes (Viscosity)

Answer 8

Larger relative molecular mass, more viscous (flow less easily). Due to stronger intermolecular forces of attraction between larger molecules

Question 9

What happens when alkanes are ignited by a spark of flame

Answer 9

Burn readily in air

Question 10

Why do alkanes make good fuels

Answer 10

Combustion of alkanes is highly exothermic, producing a lot of heat

Question 11

On what condition does complete combustion of alkanes take place and what are products formed

Answer 11

Sufficient/excess oxygen
carbon dioxide and water

Question 12

Equation for complete combustion of alkanes (Coefficients in front of reactants and products)

Answer 12

CxHy + (4x+y) / 4 O2 -> XCO2 + y/2 H2O

Question 13

On what conditions does incomplete combustion of alkanes occur and what are the possible products (3 products)

Answer 13

Insufficient oxygen
Water, carbon monoxide/carbon soot

Question 14

Colour and odour of carbon monoxide

Answer 14

Colourless and odourless

Question 15

Trends of flammability of alkanes and what type of flame is produced for alkanes with high relative molecular mass

Answer 15

With higher relative molecular mass, alkane becomes less flammable because there is higher percentage of carbon, more difficult to burn.

Sooty flame

Question 16

What is the substitution reaction of alkanes and what are the reactants as well as conditions

Answer 16

Direct replacement of an atom with another atom

Reactants: Alkanes, Halogens(Diatomic)

Condition: Presence of ultraviolet light

Question 17

What happens when methane reacts with chlorine in the presence of UV light

Answer 17

Each hydrogen atom in the methane is substituted one at a time by one of the 2 chlorine atoms. Remaining chlorine atoms= from Cl2 will form hydrogen chloride gas.

Question 18

What are the products of the substitution reaction (in reaction with ethane and chlorine gas)

Answer 18

Hydrogen chloride gas and chloroethane

Question 19

States of the 4 chloromethanes (not including methane)

Answer 19

CH3Cl (g), CH2Cl2(l), CHCl3(l), CCl4(l)

Question 20

Suggest why does the products of chloromethane vary in the first step of reaction versus the other steps

Answer 20

The relative amounts of the chloromethane is dependent on the time that the reaction is allowed to proceed

Question 21

Are alkenes saturated hydrocarbons? Why or why not

Answer 21

Unsaturated, 1 carbon-carbon double bond, 2 covalent bonds between carbon atoms

Question 22

Functional group of alkenes

Answer 22

C=C

Question 23

Are the physical properties for alkenes same as alkanes

Answer 23

Yes

Question 24

General formula of alkenes

Answer 24

CnH2n

Question 25

What is the condition for complete combustion of alkenes and products formed

Answer 25

Excess oxygen

Carbon dioxide and water vapour

Question 26

Why are alkenes more likely to undergo incomplete combustion, producing carbon monoxide and carbon compared to alkanes

Answer 26

Alkenes have a relatively higher percentage of carbon than alkanes for the same number of carbon atoms, producing sootier flames

Question 27

Why do alkenes undergo addition reaction

Answer 27

Carbon-Carbon double bonds are very reactive, thus alkenes readily undergo addition reactions

Question 28

What is the application of hydrogenation

Answer 28

Manufacture of margarine, where vegetable oil, polyunsaturated oil undergoes hydrogenation to form margarine less unsaturated

Question 28

What happens in an addition reaction

Is the product formed in addition reaction saturated. Why/Not

Answer 28

A substance is added across carbon-carbon double/triple bond in an unsaturated organic compound to form a new compound. Saturated as absence of carbon-carbon double bond

Question 29

What is hydrogenation. Product(s) formed in hydrogenation and the conditions

Answer 29

Addition of hydrogen to alkenes to form alkanes

Product: Alkane

Conditions: 180 degrees Celsius, nickel catalyst

Question 30

State 3 differences between fats and oils

Answer 30

Fats solid at room temp & pressure, oils liquid at room temp & pressure

Fats contain mainly saturated molecules while oils contain higher percentage of unsaturated molecules

Saturated fats have hydrocarbon chains that stack well with one another, causing closer packing of molecules, resulting in stronger intermolecular forces of attraction. Unsaturated hydrocarbon chains do not stack well with one another because of carbon-carbon double bond, causing bend in structure. Hydrocarbon chains cannot come as close together, not as strong intermolecular forces of attraction

Question 31

What conditions as well as reactants is required for alkene to undergo addition of bromine. Products formed and observation.

Answer 31

Reactant: Alkene and aqueous bromine/bromine water

Product: CnH2nBr2

Condition: Absence of UV light

Observation: Orange aqueous bromine decolourises rapidly, turns colourless

Question 32

If propene reacted with aqueous bromine what is the name of product formed (Hint: Draw structural formula)

Answer 32

1,2-dibromopropANE

Question 33

How to tell if a hydrocarbon is alkane or alkene

Answer 33

Addition of bromine. IF aqueous bromine remains orange, alkane. Else if it decolourises rapidly and turns from orange to colourless, alkene.

Question 34

What conditions as well as reactants is required for alkene to undergo addition of steam. Products formed.

Answer 34

Reactants: Steam

Product: Alcohol

Conditions: 300 degrees Celsius, 65 atm, phosphoric(V) acid catalyst

Question 35

What is addition polymerisation

Answer 35

Process which many smaller molecules are joined called monomers are joined together to form one giant molecule called polymers

Question 36

Similarities between alkanes and alkenes

Answer 36

Both are hydrocarbons.
Both undergo combustion to produce co2 and h2o.

Question 37

Differences between alkanes and alkenes (Not reaction/polymerisation specific)

Answer 37

Alkanes only single bonds between carbon atoms, saturated. Alkenes double bonds between carbon atoms, unsaturated.

Alkanes generally unreactive while alkenes very reactive.

Alkanes has lower carbon content produce less sooty flame. Alkenes has higher carbon content, produce more sooty flames than alkanes for same number of carbon atoms.