Alkanes

Question 1

What are alkanes

Answer 1

Alkanes are saturated aliphatic hydrocarbons. Alkanes are represented by the general formula CnH2n+2 where
n can be 1,2,3,4… etc

Question 2

Alkanes are also known as_____

Answer 2

paraffins

Question 3

_____ is an oily, thick inflammable and usually dark coloured
liquid.

Answer 3

Petroleum

Question 4

Separating the crude

petroleum into useful components is called _____

Answer 4

refining

Question 5

The first step in

refining is_____

Answer 5

fractional distillation

Question 6

what is the catalyst used in bergius process

Answer 6

Iron

Question 7

What is Fischer-Tropsch process

Answer 7

The Fischer–Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen or water gas into liquid hydrocarbons

Question 8

What is octane number

Answer 8

Octane number is a measure of the quality of gasoline: the higher the
octane number, the better the fuel.

Question 9

The quality of diesel fuel is expressed in terms of a

number called_____

Answer 9

cetane number

Question 10

Physical properties of alkanes

Answer 10

1) Alkanes are colourless and odourless.
2) They possess weak Van Der Waals forces of attraction.
3) Alkanes having 1-4 carbon atoms are gases, then from 5-17 carbon atoms they are liquid and alkanes having 18 or more carbon atoms are solid at 298K.

Question 11

Alkane molecules are very weakly polar or nonpolar because
there is very little ——————-difference between the carbon
and hydrogen atoms.

Answer 11

electro negativity

Question 12

Boiling point of alkanes ———- with the increase in the length
of the carbon chain

Answer 12

increases

Question 13

Branching in the carbon chain —————- the boiling point

Answer 13

decreases

Question 14

Alkanes are soluble in —————– solvents

Answer 14

nonpolar

Question 15

Define halogenation

Answer 15

It is defined as the replacement of hydrogen atom(s), from an
alkane molecule, by halogen atom(s)

Question 16

What is pyrolysis

Answer 16

This is a process of decomposing an organic substance by heating it to
high temperature in the absence of oxygen.
When an alkane is heated to a high temperature (at about 875 K),
it decomposes into small molecules. This process is known as
pyrolysis.

Question 17

Features of Alkanes

Answer 17

1) Alkanes are nonpolar compounds.
2) Their physical constants like
boiling point, density, etc., increase with the increase in the number
of carbon atoms.
3) Branching in the chain decreases the boiling
point

Question 18

Methods for preparing alkanes

Answer 18

Alkanes are prepared by: 
(i) Wurtz reaction, 
(ii) Kolbe’s electrolytic method
(iii) hydrogenation of unsaturated hydrocarbons, 
(iv) decarboxylation of carboxylic acids; 
(v) reduction of alkyl
halides, 
(vi) hydrolysis of Grignard reagents.

Question 19

When alkanes with six or more carbon atoms are heated under
pressure in the presence of a catalyst, _____ are
produced.

Answer 19

aromatic hydrocarbons

Question 20

The main reaction of alkanes is _____

Answer 20

combustion; heat for power

production is its chief outcome.