alkanes

Question 1

what are alkanes

Answer 1

alkanes are saturated hydrocarbons

they contain single bonds between 2 carbon atoms

Question 2

what is the general formula for an alkane

Answer 2

Cn H2n+2

where n = number of carbon atoms

Question 3

which alkane can also be called a greenhouse gas

Answer 3

Methane

Question 4

WHAT type of reaction do alkanes undergo?

Answer 4

substitution reactions

Question 5

this gas is also a saturated hydrocarbon

Answer 5

ethane

Question 6

which reagent is used to distinguish between ethane and ethene

Answer 6

alkaline potassium permanganate solution

Question 7

which forms chloroform(CHCl₃)on halogenation in the presence of sunlight

Answer 7

methane

Question 8

what is the compound formed when ethene reacts with hydrogen

Answer 8

ethane

Question 9

the conversion to ethyne to ethane is called ____

Answer 9

Hydrogenation

Question 10

the conversion to ethene to ethane is called ____

Answer 10

Hydrogenation

Question 11

_____burns with a non - luminous flame

Answer 11

methane

Question 12

3 uses of methane

Answer 12

• -used as a domestic fuel
• -used in the manufacture of hydrogen and carbon monoxide
• -it is used in natural gas an alternative fuel in place of gasoline

Question 13

what is pyrolysis

Answer 13

the process of decomposition of a hydrocarbon into elements on heating in the absence of air

Ch4 —-> C + 2H2
1000 degree celcius

Question 14

what are the physical properties of ethane

Answer 14

• –> colourless and odourless gas
• —>vapour density is 1.5
• —>sparingly soluble in water
• —>soluble in organic solvents

Question 15

what are the physical properties of methane

Answer 15

• –> it is lighter than air
• –>it is insoluble in water but soluble in organic solvents
• –>it is a colourless and odourless gas

Question 16

what is halogenation

Answer 16

it involves the replacement of hydrogen atoms of methane with halogen atoms

Question 17

how is ethane gas collected

Answer 17

downward displacement of water

Question 18

define cracking

Answer 18

when a bigger hydrocarbon breaks into smaller fragments it is called cracking.

there are 2 types of cracking thermal and catalytic

Question 19

define thermal cracking

Answer 19

thermal cracking is when alkanes are heated to high temperature in the absence of air

they decompose into a mixture of saturated and unsaturated hydrocarbons and hydrogens

Ch4 —> C + 2H2 (1000 celcius)

Question 20

define catalytic cracking

Answer 20

catalytic cracking is when alkanes are treated with a catalyst in the absence of air

they decompose into a mixture of saturated and unsaturated hydrocarbons and hydrogens

C2H6 —> CH2 = CH2 + H2 (SiO2 - Al2O3)

Question 21

3 uses of ethane

Answer 21

• —> used as an industrial fuel
• —> used in precipitation of ethyl chloride
• —> it is used in the preparation of ethanol, ethanal and ethanoic acid

Question 22

________ is required for the reaction of ethane with chlorine

Answer 22

diffused sunlight

Question 23

why is methane known as marsh gas

Answer 23

Methane is called Marsh Gas. Because it isproduced when vegetation decomposes naturally within some geographicalmarshes,swamps, andbogs.

Question 24

direct iodination for methane is not carried

Answer 24

Iodine reacts with methane reversibly. When iodine reacts with methane, it gives iodomethane and hydrogen iodide which is a strong reducing agent and it can convert to iodomethane back to methane.

CH4 + I2 –> CH3I + HI

To overcome this difficulty iodination is carried out in the presence of strong oxidizing agents like HIO3 which oxidize HI formed during the reaction.

HIO3 + 5 H I —>3H2O + 𝒊2