Week 6 Flashcards
Alkanes are the ________ and _______reactive hydrocarbon species containing c and h atoms
simplest
least
Its structural feature singly bonded C-C and C-H or a _______
lack of unsaturation
______ alkanes and ______ alkanes have different physical and chemical properties
straight-chain
branched
Alkanes can exist as ___, ____, ____ at room temperature
gas, liquid, solids
Alkanes contain only C-C and C-H sigma bonds which are ______ ______ due to very small difference of electronegativity between carbon and hydrogen
almost nonpolar
(True or False)
Alkanes possess strong Van der Waals’ forces as the intermolecular forces
False
(weak van der waals forces)
(True or False)
Alkanes possess weak dipole-dipole forces as the intermolecular forces
False
(van der waals forces)
First four carbon members exist as
gases
C5 to C17 exist as
liquids
C18 and up exist as
waxy solids
(True or False)
Solid alkanes are normally hard with high melting point
False
(soft; low)
(True or False)
Solid alkanes are normally soft with low melting point due to strong repulsive forces generated between electrons on neighboring atoms
True
The strong repulsive forces ______ the weak van der waals forces of attraction
counterbalance
(True or False)
Intermolecular forces (IMFs) exist between atoms in a molecule
False
(exist between molecules)
Types of Intermolecular Forces (IMFs)
(1) Van der Waals Forces
(2) Dipole-dipole
(3) Hydrogen Bonding
(True or False)
Van der Waals Forces is the strongest
False
(weakest)
(True or False)
Hydrogen Bonding is the strongest
True
Intramolecular forces exist between ________
atoms in a molecule
Types of Intramolecular forces
(1) Electrostatic/Ionic bond
(2) Covalent bond
(3) Metallic bond
(True or False)
As the elevation increases, pressure increases
False
(decreases)
(True or False)
As the carbon increases, boiling point increases, molecular weight increases
True
Alkanes with even carbon atoms have ______ melting points than those with an odd number of carbon atoms
higher
(True or False)
As the branching increases, boiling point decreases
True
(True or False)
Branching increases, surface area increases, van der waals forces increases
False
(surface area reduces, van der waals forces reduces)
(True or False)
Volatility decreases with decrease in chain length
False
(increase in chain length)
(True or False)
The more the branching, the lower is the volatility
False
(the greater the volatility)
(True or False)
The lower the volatility, the lower the boiling point
True
(True or False)
The densities of alkanes increase with increase molecular masses but become constant at about 0.10 g/cm^3
False
(0.8 g/cm^3)
(True or False)
All alkanes are lighter than water
True
(True or False)
Densities does not varies with temperature
False
(varies)
(True or False)
Alkanes are soluble in both water and organic solvents
False
(not soluble in water)
In water, the primary intermolecular attractions are
hydrogen bonds
are chemical species which, in the course of chemical reactions, acquire electrons, or a share in electrons, from other molecules or ions.
Electrophilic reagents
is a chemical reaction with oxygen in which alkane is converted into carbon dioxide and water with the release of heat energy
combustion (oxidation)
The heat released on complete combustion of one mole of a substance is called _______ and the reaction is called _______
heat combustion; exothermic
(True or False)
In exothermic, they give off heat
True
(True or False)
Alkanes can not be used as a source of energy
False
(can be used)
(True or False)
Product and coefficients change
False
(only the coefficients)
Is a substitution reaction wherein one or more hydrogen atoms is/ are replaced by halogen atom/s
Halogenation
(True or False)
Chlorinations and brominations are normally endothermic
False
(exothermic)
This reaction is done by heating the HC with the vapors of nitric acid at 420° C
Nitration
(True or False)
Nitration is done by heating the HC with the vapors of nitric acid at 189 ° C
False
(420° C)
The complex alkanes with high molecular weights that are found in crude oil are frequently broken into smaller, more useful alkanes by _________
Thermal cracking
Thermal cracking is typically performed at _______ and often in the presence of a _______
high temperature; catalyst
Alkenes and alkanes can be separated by
Fractional distillation
The cleavage of C-C and C-H bonds under the influence of heat is called
Pyrolysis
Pyrolysis in petroleum industry is known as
Cracking
This process is important in modifying the carbon chain length of higher hydrocarbons obtained by the distillation of crude oil
Cracking
The conversion of long chain aliphatic hydrocarbons into aromatic hydrocarbons with the same number of carbon atoms is called
Reforming
Catalytic hydrogenation is also called
Sabatier- Sendern’s reactions or S-S reactions
It is used for symmetrical alkanes
Wurtz reaction
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
Decarboxylation
