carbon and its compounds Flashcards
what is covalent bond
The bond which are formed by the sharing of an electron pair between the atoms either same or different is known as covalent bond.
properties of covalent bond in carbon
It has four electrons in its outermost shell and
needs to gain or lose four electrons to attain
noble gas configuration.
(i) Gain four electrons forming C4– anion.
Difficult for the nucleus with six protons
to hold on to ten electrons.
(ii ) Lose four electrons forming C4+ cation.
Require a large amount of energy to re
move four electrons.
Properties of covalent bond
- The boiling and melting points of the carbon compounds, we find that these compounds have low melting and boiling points as compared to ionic compounds.
- We can conclude that the forces of attraction between the molecules are not very strong.
- Since these compounds are largely non-conductors of electricity.
- We can conclude that the bonding in these compounds does not give rise to any ions.
Properties of Carbon
(i) Carbon has the unique ability to form
bonds with other atoms of carbon, giving
rise to large molecules. This property is
called catenation.
(ii) Tetravalency of Atom:- Carbon has a va
lency of four. It is capable of bonding with
four other atoms of carbons or atoms of
some other mono-valent element. Many
other elements giving rise to compounds
with specific properties which depend on
the elements other than carbon present in
the molecule.
(iii) Carbon also forms bonds with other elements such as halogens, oxygen, nitrogen
and Sulphur. In a hydrocarbon chain, one
or more hydrogens can be replaced by
these elements, such that the valency of
carbon remains satisfied. In such com
pounds, the element replacing hydrogen is
referred to as a heteroatom.
what is heteroatom?
Carbon also forms bonds with other ele
ments such as halogens, oxygen, nitrogen
and Sulphur. In a hydrocarbon chain, one
or more hydrogens can be replaced by
these elements, such that the valency of
carbon remains satisfied. In such com
pounds, the element replacing hydrogen is
referred to as a heteroatom.
what are hydrocarbons
A hydrocarbon chain is a structure made of carbon and hydrogen atoms.
In this chain, one or more hydrogen atoms can be replaced by other elements (e.g., halogens, oxygen, nitrogen, sulphur) without disrupting the structure.
What are Saturated Hydrocarbons?
The hydrocarbons in which all the carbon atoms are linked by only single covalent bonds
are called saturated hydrocarbons or alkanes
or paraffins.
The general formula of these compounds is CnH2n + 2, where, n = number of carbons atoms in one molecule of a hydrocarbon.
What are Unsaturated Hydrocarbons?
The hydrocarbons in which at least one double
or triple bond (or multiple bond) is present
along with single bonds are called unsaturated compounds.
Alkenes
Carbon compounds which have at least one
double bond along with single bond.
CnH2n
Alkynes
Carbon compounds having one or more triple
bond along with single bond.
CnH2n-2
What are functional groups?
Heteroatoms and group containing these confer
specific properties to the compound. These
groups are called functional group.
What is homologous series
- Same functional group.
- Similar chemical properties.
- Regular increase in physical properties.
- Successive numbers differ by –CH2 group.
what is isomerism?
Compounds with same molecular formula, but
different structure.
The difference in properties of these com
pounds is due to the difference in their struc
tures. These compounds have identical molec
ular formula but different structures. Hence
they are called structural isomers and phenomenon is called structural isomerism.
How many structural isomers can you
draw for pentane?
Pentane (C₅H₁₂) has three structural isomers. These are:
n-Pentane: The straight-chain isomer with all five carbon atoms in a row.
Structural formula: CH₃-CH₂-CH₂-CH₂-CH₃
Isopentane (Methylbutane): A branched isomer where a methyl group (-CH₃) is attached to the second carbon of butane.
Structural formula: CH₃-CH(CH₃)-CH₂-CH₃
Neopentane (Dimethylpropane): A branched isomer where two methyl groups (-CH₃) are attached to the central carbon atom of a propane chain.
Structural formula: (CH₃)₂C-CH₂-CH₃
These are the three structural isomers of pentane.
CHEMICAL PROPERTIES OF CARBON
COMPOUNDS
COMBUSTION:
All the carbon compounds (including its allo
tropic forms also) burn in oxygen to give car
bon dioxide and water vapours. Heat and light
are also released during this process. This reaction is called as combustion.
C + O2 → CO2 + Heat + Light
CH4 + 202 → CO2 + 2H2O + Heat + Light
CH3CH2OH + 3O2 → 2CO₂ + 3H₂O + Heat + Light
Saturated hydrocarbons give a clean blue flame
due to their complete combustion whereas, un
saturated hydrocarbons give a yellow flame
with lots of black smoke as they do not under
go complete combustion.
Differentiate flames b/w saturated and unsaturated hydrocarbons
Saturated hydrocarbons give a clean blue flame
due to their complete combustion whereas, un
saturated hydrocarbons give a yellow flame
with lots of black smoke as they do not under
go complete combustion.
Oxidation
It is the reaction involving the addition of oxy
gen and removal of hydrogen. Alcohols can be
oxidised to carboxylic acid by heating them
either in presence of oxidising agents like alka
line KMnO4 (potassium permanganate) or
acidified K2Cr2O7 (potassium dichromate).
Take some carbon compounds (naphthalene, camphor, alcohol) one by one on a spatula and burn them. Observe the nature of the flame and note whether smoke is produced. Place a metal plate above the flame. Is there a deposition on the plate in case of any of the compounds?
Ans :
(i) Camphor & Naphthalene are unsaturated hydrocarbons. So they burn with yellow flame and leave residues. Alcohol is saturated and burns with a clean blue flame.
(ii) There is deposition in the case of naphthalene and camphor on the plate.
Allotropes of carbon
The element carbon occurs in different forms in nature with widely varying physical properties.
Both diamond and graphite are formed by carbon atoms, the difference lies in the manner in which the carbon atoms are bonded to one another.
In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure.
In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array.
One of these bonds is a double-bond, and thus the valency of carbon is satisfied.
These two different structures result in diamond and graphite having very different physical properties even though their chemical properties are the same.
Diamond is the hardest substance known while graphite is smooth and slippery.
Graphite is also a very good conductor of electricity unlike other non-metals
Light a bunsen burner and adjust the air hole at the base to get different types of flames/presence of smoke. When do you get a yellow, sooty flame? When do you get a blue flame?
Flame Types:
Blue flame (complete combustion, sufficient oxygen).
Yellow, sooty flame (incomplete combustion, insufficient oxygen).
Saturated Hydrocarbons:
Burn with a blue flame in sufficient oxygen.
Burn with a yellow, sooty flame if oxygen is insufficient or air holes are blocked.
Unsaturated Hydrocarbons:
Typically burn with a yellow, sooty flame.
Practical Insights:
Air inlets in stoves ensure a clean blue flame.
Blackened cooking vessels indicate incomplete combustion and wasted fuel.
Combustion Explanation:
Complete combustion: Produces carbon dioxide, water, and light (blue flame).
Incomplete combustion: Produces soot and smoke (yellow flame).
Environmental Note:
Fuels like coal and petroleum release nitrogen and sulfur oxides, which are pollutants.
Addition Reactions
The reaction in which a reagent completely
add to a reactant without the removal of small
molecules are called addition reactions.
reaction is commonly used in the
hydrogenation of vegetable oils [that are un
saturated compounds] using a nickel catalyst.
SUBSTITUTION REACTIONS
The reactions in which a reagent replaces an
atom or a group of atoms from the reactant
(substrate) are called substitution reactions.
These are generally shown by saturated com
pounds.
Most of the saturated hydrocarbons are fairly
inert and unreactive in the presence of most
reagents. However, these reactions take place
readily in the presence of sunlight.
Take about 3 mL of ethanol in a test tube and warm it gently in a water bath.
Add a 5% solution of alkaline potassium permanganate drop by drop to this solution.
Does the colour of potassium permanganate persist when it is added initially?
Answer
* The purple colour of potassium permanganate disappears initially.
Why does the colour of potassium permanganate not disappear when excess is added?
Answer
* Because all the alcohol gets consumed and the reaction stops.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction
Reason: A molecule of ethanol contains six hydrogen atoms while that of ethanoic acid contains four hydrogen atoms since oxidation involves removal of hydrogen, therefore conversion of ethanol to ethanoic acid is an oxidation reaction.
Q. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used
The oxygen-ethyne flame is extremely hot and produces a very high temperature which is used for welding metals. A mixture of ethyne and air is not used for welding because burning of ethyne in air produces a sooty flame due to incomplete combustion, which is not hot enough to melt metals for welding.
Properties of Ethanol
Its common name is ethyl and formula is
C2H5OH or CH3CH2OH
Ethanol is a liquid at room temperature
Ethanol is commonly called alcohol and is the active ingredient of all alcoholic drinks. In addition, because it is a good solvent, it is also used in medicines such as tincture iodine, cough syrups, and many tonics. Ethanol is also soluble in water in all proportions. Consumption of small quantities of dilute ethanol causes drunkenness. Even though this practice is condemned, it is a socially widespread practice. However, intake of even a small quantity of pure ethanol (called absolute alcohol) can be lethal. Also, long-term consumption of alcohol leads to many health problems
freezes to form a colorless, ice-like solid
which looks like a glacier. Due to this,
pure ethanoic acid is called glacial ethano
ic caid or glacial acetic acid.).
Preparation:
Alcohol (ethanol) is obtained by the fermenta
tion of molasses which are obtained from sug
arcane juice.
Reaction of ethanol and sodium
Ethyl alcohol reacts with sodium metal
leading to the evolution of hydrogen gas.
Hydrogen gas burns with a pop sound
dehydration of ethanol
Removal of water molecules from a com
pound is known as dehydration reaction.
When ethanol is heated at 443k with ex
cess conc, H2SO4, the water molecules get
removed from it and ethene is obtained.
How can ethanol and ethanoic acid be differentiated on the basis of their physical
and chemical properties?
Ethanol, and ethanoic acid both are different compounds formed from the ethane molecule. They differ on the basis of their physical, and chemical properties like smell, melting point, boiling point, and in terms of chemical properties, it differs in case of reactions with the different compounds.
Explain the formation of scum when hard
water is treated with soap.
When soap is dissolved in hard water, it reacts with the calcium and magnesium ions that are present there and form calcium and magnesium salt of fatty acids. These salts are not miscible in water at all and form a white layer on the surface of the water called scum.
Explain the mechanism of the cleaning
action of soaps.
When soap is added to an oily or greasy part of cloth, the hydrocarbon part of soap dissolves in oil, keeping the head away from the oil. Big molecules of oil and soap break by rubbing into small, emulsified oil droplets in water, which are washed away by stream of water.
Why is acetic acid weaker in acidity compared to HCl but more acidic than alcohol?
Weak acidity of acetic acid as compared to HCI is because of its low
ionisation but is more acidic than alcohol
is because of the more stability of ion
formed after the removal of a proton (H).
It evolves hydrogen gas when reacts with
sodium metal.
2CH3COOH + 2Na → CH3COONa+ +
H2O
What happens when ethanoic acid reacts with a base like sodium hydroxide? Write the chemical equation for the reaction.
Ethanoic Acid is a
weak acid. Like any acid, it reacts with a
base to form one molecule of salt and one
molecule of water. An example of this re
action is given below where Ethanoic acid
is reacting with Sodium Hydroxide (a
base) to form sodium ethanoate and water:
CH3COOH + NaOH → CH3COONa+ +
H2O
Esterification Reaction:
When any car
boxylic acid reacts with any alcohol, it
leads to the formation of another class of
chemical compounds named esters. This
reaction which leads to the formation of
esters is known as the esterification reaction. Given below is an example presented
when the Ethanoic Acid (a carboxylic acid) reacts with Ethanol (ethyl alcohol) resulting in the formation of ethyl ethanoate
(an ester)
CH3COOH + CH3CH2OH →
CH3COOCH2CH3 + H2O
saponification
The ester gets converted back into alcohol
and sodium salt of acid when treated with
alkali like sodium hydroxide. This reac
tion is called saponification, as it is used
for the preparation of soap.
CH3COOC2H5 + NaOH → CH3COONa +
C2H3OH
What happens when ethanoic acid reacts with carbonates or hydrogen carbonates? Provide the chemical equations for these reactions.
When Ethanoic acid is reacted with carbonates or hydrogen
derivatives of carbonates
(hydrogen carbonates, also commonly known as the bicarbonates), it leads to the
formation of salt, and carbon dioxide and water as by-products. Examples in which
Ethanoic acid is reacted with sodium carbonate and sodium bicarbonate are given
below:
2CH3COOH + Na2CO3 → 2CH3COONa +
CO2 + H2O
CH3COOH + NaHCO3 → CH3COONa +
CO2 + H2O
Drop a small piece of sodium, about the size of a couple of grains of rice, into ethanol (absolute alcohol). What do you observe? How will you test the gas evolved?
If a small piece of sodium is dropped into ethanol, it reacts steadily to give off bubbles of hydrogen gas and leaves a colorless solution of sodium ethoxide: CH3CH2ONa. The anion component is an alkoxide.
Properties of Ethanoic Acid
Ethanoic acid is commonly called acetic acid and belongs to a group of acids called carboxylic acids. 5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles. The melting point of pure ethanoic acid is 290 K and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid. The group of organic compounds called carboxylic acids are obviously characterised by their acidic nature. However, unlike mineral acids like HCl, which are completely ionised, carboxylic acids are weak acids.
USES OF ACETIC ACID
It is used as a solvent for various reactions
which require aprotic solvent.
* It is used in the production of vinegar, es
ters, and synthetic polymers.
* It is used as a blood cell lysing agent in
laboratories.
* It is used as an antifungal agent.
what are soaps made of
Soaps are sodium or potassium salts of long
chain carboxylic acids and have general formu
la RCOONa+
Where, R = C15 H31 , C17 H35 etc.
what soapless soap
Detergents are usually ammonium or sulphate
salts of long chain carboxylic acids. They are
also called as soapless soap.
STRUCTURE OF A SOAP MOLECULE
A soap molecule is made up of two parts - a
long hydrocarbon part (or non - ionic part) and
a short ionic part containing —COONa+ group.
The long hydrocarbon part is hydrophobic and
therefore insoluble in water but soluble in soil.
The ionic portion of the soap molecule is hydrophilic so, soluble in water and insoluble in
oil.
CLEANSING ACTION OF SOAPS
At the surface of water, the hydrophobic end or
tail of soap will be insoluble in water and the
soap will align along the surface of water with
the ionic end in water and the hydrocarbon
‘tail’ protruding out of water.
Inside water, these molecules show a unique
orientation that keeps the hydrocarbon portion
out of the water. This is done by forming clusters of molecules in which the hydrophobic
tails are in the interior of the cluster and on the
surface of cluster, ionic ends are present.
This formation of cluster of molecules is called
micelle. To wash away the loosened dirt particles in the form of micelles. Hence, the dirt
suspended in the micelles is also easily rinsed
away.
detergents
Sometime while bathing that foam is formed
with difficulty and an insoluble substance
(scum) remains after washing with water. This
is caused by the reaction of soap with the calci
um and magnesium salts, which cause the
hardness of water.
This problem is overcome by using another
class of compounds called detergents as
cleansing agents. Detergents are generally sodium salts of sulphonic acids or ammonium
salts with chlorides or bromides ions etc. Both
have long hydrocarbon chain.
The charged ends of these compounds do not
form insoluble precipitates with the calcium
and magnesium ions in hard water.
Compare the pH of dilute acetic acid and dilute hydrochloric acid using both litmus paper and universal indicator.
Are both acids indicated by the litmus test?
Does the universal indicator show them as equally strong acids?
Answer: Yes.
Answer: No.
Take 1 mL ethanol (absolute alcohol) and 1 mL glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube. n Warm in a water-bath for at least five minutes as shown in Fig. 4.11. n Pour into a beaker containing 20-50 mL of water and smell the resulting mixture.
The resulting mixture is an ester. Esters have sweet smell
Set up the apparatus as shown in Chapter 2, Activity 2.5.
Take a spatula full of sodium carbonate in a test tube and add 2 mL of dilute ethanoic acid.
What do you observe?
Pass the gas produced through freshly prepared lime-water. What do you observe?
Can the gas produced by the reaction between ethanoic acid and sodium carbonate be identified by this test?
Repeat this Activity with sodium hydrogen carbonate instead of sodium carbonate.
Answer: Following reaction occurs:
2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O (Sodium acetate)
Answer: Lime-water turns milky. It means that the gas is CO2.
Answer: Yes. The gas is CO2.
Answer: Reaction with sodium hydrogen carbonate:
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
Take about 10 mL of water each in two test tubes.
Add a drop of oil (cooking oil) to both the test tubes and label them as A and B.
To test tube B, add a few drops of soap solution.
Now shake both the test tubes vigourously for the same period of time.
Can you see the oil and water layers separately in both the test tubes immediately after you stop shaking them?
Leave the test tubes undisturbed for some time and observe. Does the oil layer separate out? In which test tube does this happen first?
Answer: No.
Answer: Yes. The oil layer separates out in both test tubes. But this happens first in test tube A.
Take about 10 mL of distilled water (or rainwater) and 10 mL of hard water (from a tubewell or hand pump) in separate test tubes.
Add a couple of drops of soap solution to both.
Shake the test tubes vigorously for an equal period of time and observe the amount of foam formed.
In which test tube do you get more foam?
In which test tube do you observe a white curdy precipitate?
Answer: In the test tube containing distilled water.
Answer: In the test tube containing hard water.
Take two test tubes with about 10 mL of hard water in each.
Add five drops of soap solution to one and five drops of detergent solution to the other.
Shake both test tubes for the same period.
Do both test tubes have the same amount of foam?
In which test tube is a curdy solid formed?
Answer: No. The test tube containing detergent has more foam.
Answer: In the test tube containing soap.
Common Salt
NaCl
NaOH + HCL –> NaCl + H2O
Caustic Soda
NaOH
2NaCl +2H2O –> 2NaOH +Cl2 + H2
- Paper
- bleach
- detergent
Washing Soda
Na2CO3 . 10H2O
- glass
-laundry
- soften hard water
Baking soda
NaHCo3
Nacl + NH3 + CO2 + H2O –> NaHCO3 + NH4Cl
- prepare baking soda
- remove acidity
- fire extinguisher
Bleaching Powder
CaOCl2
chloroform
cotton textile
chemical
