Week 6

Question 1

Alkanes are the ________ and _______reactive hydrocarbon species containing c and h atoms

Answer 1

simplest
least

Question 2

Its structural feature singly bonded C-C and C-H or a _______

Answer 2

lack of unsaturation

Question 3

______ alkanes and ______ alkanes have different physical and chemical properties

Answer 3

straight-chain
branched

Question 4

Alkanes can exist as ___, ____, ____ at room temperature

Answer 4

gas, liquid, solids

Question 5

Alkanes contain only C-C and C-H sigma bonds which are ______ ______ due to very small difference of electronegativity between carbon and hydrogen

Answer 5

almost nonpolar

Question 6

(True or False)
Alkanes possess strong Van der Waals’ forces as the intermolecular forces

Answer 6

False
(weak van der waals forces)

Question 7

(True or False)
Alkanes possess weak dipole-dipole forces as the intermolecular forces

Answer 7

False
(van der waals forces)

Question 8

First four carbon members exist as

Answer 8

gases

Question 9

C5 to C17 exist as

Answer 9

liquids

Question 10

C18 and up exist as

Answer 10

waxy solids

Question 11

(True or False)
Solid alkanes are normally hard with high melting point

Answer 11

False
(soft; low)

Question 12

(True or False)
Solid alkanes are normally soft with low melting point due to strong repulsive forces generated between electrons on neighboring atoms

Answer 12

True

Question 13

The strong repulsive forces ______ the weak van der waals forces of attraction

Answer 13

counterbalance

Question 14

(True or False)
Intermolecular forces (IMFs) exist between atoms in a molecule

Answer 14

False
(exist between molecules)

Question 15

Types of Intermolecular Forces (IMFs)

Answer 15

(1) Van der Waals Forces
(2) Dipole-dipole
(3) Hydrogen Bonding

Question 16

(True or False)
Van der Waals Forces is the strongest

Answer 16

False
(weakest)

Question 17

(True or False)
Hydrogen Bonding is the strongest

Answer 17

True

Question 18

Intramolecular forces exist between ________

Answer 18

atoms in a molecule

Question 19

Types of Intramolecular forces

Answer 19

(1) Electrostatic/Ionic bond
(2) Covalent bond
(3) Metallic bond

Question 20

(True or False)
As the elevation increases, pressure increases

Answer 20

False
(decreases)

Question 21

(True or False)
As the carbon increases, boiling point increases, molecular weight increases

Answer 21

True

Question 22

Alkanes with even carbon atoms have ______ melting points than those with an odd number of carbon atoms

Answer 22

higher

Question 23

(True or False)
As the branching increases, boiling point decreases

Answer 23

True

Question 24

(True or False)
Branching increases, surface area increases, van der waals forces increases

Answer 24

False
(surface area reduces, van der waals forces reduces)

Question 25

(True or False) Volatility decreases with decrease in chain length

Answer 25

False (increase in chain length)

Question 26

(True or False) The more the branching, the lower is the volatility

Answer 26

False (the greater the volatility)

Question 27

(True or False) The lower the volatility, the lower the boiling point

Answer 27

True

Question 28

(True or False) The densities of alkanes increase with increase molecular masses but become constant at about 0.10 g/cm^3

Answer 28

False (0.8 g/cm^3)

Question 29

(True or False) All alkanes are lighter than water

Answer 29

True

Question 29

(True or False) Densities does not varies with temperature

Answer 29

False (varies)

Question 30

(True or False) Alkanes are soluble in both water and organic solvents

Answer 30

False (not soluble in water)

Question 31

In water, the primary intermolecular attractions are

Answer 31

hydrogen bonds

Question 32

are chemical species which, in the course of chemical reactions, acquire electrons, or a share in electrons, from other molecules or ions.

Answer 32

Electrophilic reagents

Question 33

is a chemical reaction with oxygen in which alkane is converted into carbon dioxide and water with the release of heat energy

Answer 33

combustion (oxidation)

Question 34

The heat released on complete combustion of one mole of a substance is called _______ and the reaction is called _______

Answer 34

heat combustion; exothermic

Question 35

(True or False) In exothermic, they give off heat

Answer 35

True

Question 36

(True or False) Alkanes can not be used as a source of energy

Answer 36

False (can be used)

Question 37

(True or False) Product and coefficients change

Answer 37

False (only the coefficients)

Question 38

Is a substitution reaction wherein one or more hydrogen atoms is/ are replaced by halogen atom/s

Answer 38

Halogenation

Question 39

(True or False) Chlorinations and brominations are normally endothermic

Answer 39

False (exothermic)

Question 40

This reaction is done by heating the HC with the vapors of nitric acid at 420° C

Answer 40

Nitration

Question 41

(True or False) Nitration is done by heating the HC with the vapors of nitric acid at 189 ° C

Answer 41

False (420° C)

Question 42

The complex alkanes with high molecular weights that are found in crude oil are frequently broken into smaller, more useful alkanes by _________

Answer 42

Thermal cracking

Question 43

Thermal cracking is typically performed at _______ and often in the presence of a _______

Answer 43

high temperature; catalyst

Question 44

Alkenes and alkanes can be separated by

Answer 44

Fractional distillation

Question 45

The cleavage of C-C and C-H bonds under the influence of heat is called

Answer 45

Pyrolysis

Question 46

Pyrolysis in petroleum industry is known as

Answer 46

Cracking

Question 47

This process is important in modifying the carbon chain length of higher hydrocarbons obtained by the distillation of crude oil

Answer 47

Cracking

Question 48

The conversion of long chain aliphatic hydrocarbons into aromatic hydrocarbons with the same number of carbon atoms is called

Answer 48

Reforming

Question 49

Catalytic hydrogenation is also called

Answer 49

Sabatier- Sendern's reactions or S-S reactions

Question 50

It is used for symmetrical alkanes

Answer 50

Wurtz reaction

Question 51

Reaction where Na-salt of carboxylic acid is heated with soda lime (NaOH & CaO), alkane is obtained having one carbon less than salt by removal of a molecule of CO2

Answer 51

Decarboxylation