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- (d) All the above
- (b) Liquefied Petroleum Gas
- (c) Structural
- (d) chain
- (a) compressed natural gas
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The phenomenon of the existence of two or more compounds possessing the same molecular formula but different properties is known as isomerism. Such compounds are called isomers. Compounds having the same molecular formula but different structures (manners in which atoms are linked) are classified as structural isomers. Structural isomers are classified as chain isomer, position isomer, functional group isomer. Meristematic arises due to different alkyl chains on either side of the functional group in the molecule and stereoisomerism and can be classified as geometrical and optical isomerism. Hyperconjugation is a general stabilising interaction. It involves delocalisation of $\sigma$ electrons of the C-H bond of an alkyl group directly attached to an atom of an unsaturated system or to an atom with an unshared p orbital. This type of overlap stabilises the carbocation because electron density from the adjacent $\sigma$ bond helps in dispersing the positive charge.
1. Why Isopentane, pentane and Neopentane are chain isomers?
2. The molecular formula $C _3 H _8 O$ represents which isomer?
3. What type of isomerism is shown by Methoxypropane and ethoxyethane?
OR
Why hyperconjugation is a permanent effect?
→1. Why Isopentane, pentane and Neopentane are chain isomers?
2. The molecular formula $C _3 H _8 O$ represents which isomer?
3. What type of isomerism is shown by Methoxypropane and ethoxyethane?
OR
Why hyperconjugation is a permanent effect?
The idea of oxidation number has been invariably applied to define oxidation, reduction, oxidising agent (oxidant), reducing agent (reductant) and the redox reaction. To summarise, we may say that:
Oxidation: An increase in the oxidation number of the element in the given substance.
Reduction: A decrease in the oxidation number of the element in the given substance.
Oxidising agent: A reagent which can increase the oxidation number of an element in a given substance. These reagents are called as oxidants also.
Reducing agent: A reagent which lowers the oxidation number of an element in a given substance. These reagents are also called as reductants.
Redox reactions: Reactions which involve change in oxidation number of the interacting species.
Types of Redox Reactions
1.) Combination reactions -A combination reaction may be denoted in the manner:
A + B → C
Either A and B or both A and B must be in the elemental form for such a reaction to be a redox reaction. All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen, are redox reactions. Some important examples of this category are:
2.) Decomposition reactions- Decomposition reactions are the opposite of combination reactions. Precisely, a decomposition reaction leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state.
Examples of this class of reactions are:
It may carefully be noted that there is no change in the oxidation number of hydrogen in methane under combination reactions and that of potassium in potassium chlorate in reaction. This may also be noted here that all decomposition reactions are not redox reactions. For example, decomposition of calcium carbonate is not a redox reaction.
3.) Displacement reactions- In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. It may be denoted as:
X + YZ → XZ + Y
Displacement reactions fit into two categories: metal displacement and non-metal displacement.
(a) Metal displacement: A metal in a compound can be displaced by another metal in the uncombined state. Metal displacement reactions find many applications in metallurgical processes in which pure metals are obtained from their compounds in ores.
(b) Non-metal displacement: The non-metal displacement redox reactions include hydrogen displacement and a rarely occurring reaction involving oxygen displacement. All alkali metals and some alkaline earth metals (Ca, Sr, and Ba) which are very good reductants, will displace hydrogen from cold water. Many metals, including those which do not react with cold water, are capable of displacing hydrogen from acids. Dihydrogen from acids may even be produced by such metals which do not react with steam. Cadmium and tin are the examples of such metals.
4.) Disproportionation reactions – Disproportionation reactions are a special type of redox reactions. In a disproportionation reaction an element in one oxidation state is simultaneously oxidised and reduced. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least three oxidation states. The element in the form of reacting substance is in the intermediate oxidation state; and both higher and lower oxidation states of that element are formed in the reaction. The decomposition of hydrogen peroxide is a familiar example of the reaction, where oxygen experiences disproportionation.
Here the oxygen of peroxide, which is present in –1 state, is converted to zero oxidation state in O2 and decreases to –2 oxidation state in H2O.
Oxidation: An increase in the oxidation number of the element in the given substance.
Reduction: A decrease in the oxidation number of the element in the given substance.
Oxidising agent: A reagent which can increase the oxidation number of an element in a given substance. These reagents are called as oxidants also.
Reducing agent: A reagent which lowers the oxidation number of an element in a given substance. These reagents are also called as reductants.
Redox reactions: Reactions which involve change in oxidation number of the interacting species.
Types of Redox Reactions
1.) Combination reactions -A combination reaction may be denoted in the manner:
A + B → C
Either A and B or both A and B must be in the elemental form for such a reaction to be a redox reaction. All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen, are redox reactions. Some important examples of this category are:
2.) Decomposition reactions- Decomposition reactions are the opposite of combination reactions. Precisely, a decomposition reaction leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state.
Examples of this class of reactions are:
It may carefully be noted that there is no change in the oxidation number of hydrogen in methane under combination reactions and that of potassium in potassium chlorate in reaction. This may also be noted here that all decomposition reactions are not redox reactions. For example, decomposition of calcium carbonate is not a redox reaction.
3.) Displacement reactions- In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. It may be denoted as:
X + YZ → XZ + Y
Displacement reactions fit into two categories: metal displacement and non-metal displacement.
(a) Metal displacement: A metal in a compound can be displaced by another metal in the uncombined state. Metal displacement reactions find many applications in metallurgical processes in which pure metals are obtained from their compounds in ores.
(b) Non-metal displacement: The non-metal displacement redox reactions include hydrogen displacement and a rarely occurring reaction involving oxygen displacement. All alkali metals and some alkaline earth metals (Ca, Sr, and Ba) which are very good reductants, will displace hydrogen from cold water. Many metals, including those which do not react with cold water, are capable of displacing hydrogen from acids. Dihydrogen from acids may even be produced by such metals which do not react with steam. Cadmium and tin are the examples of such metals.
4.) Disproportionation reactions – Disproportionation reactions are a special type of redox reactions. In a disproportionation reaction an element in one oxidation state is simultaneously oxidised and reduced. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least three oxidation states. The element in the form of reacting substance is in the intermediate oxidation state; and both higher and lower oxidation states of that element are formed in the reaction. The decomposition of hydrogen peroxide is a familiar example of the reaction, where oxygen experiences disproportionation.
Here the oxygen of peroxide, which is present in –1 state, is converted to zero oxidation state in O2 and decreases to –2 oxidation state in H2O.
- In … an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element.
- displacement reaction
- decomposition reaction
- disproportionation reaction
- combination reaction
- leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state.
- displacement reaction
- decomposition reaction
- disproportionation reaction
- combination reaction
- In …. an element in one oxidation state is simultaneously oxidised and reduced.
- displacement reaction
- decomposition reaction
- disproportionation reaction
- combination reaction
- Reactions which involve change in oxidation number of the interacting species…
- Exothermic reaction
- Endothermic reaction
- Neutralization reaction
- Redox reaction
- One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least … oxidation states.
- 1
- 2
- 3
- 4
Read the passage given below and answer the following questions from (i) to (iii). Le Chatelier’s principle is also known as the equilibrium law, used to predict the effect of change on a system at chemical equilibrium. This principle states that equilibrium adjusts the forward and backward reactions in such a way as to accept the change affecting the equilibrium condition. When factor-like concentration, pressure, temperature, inert gas that affect equilibrium are changed, the equilibrium will shift in that direction where the effects caused by these changes are nullified. This principle is also used to manipulate reversible reactions in order to obtain suitable outcomes.
→- Which one of the following conditions will favour the maximum formation of the product in the reaction?
$\text{A}_{2(\text{g})}+\text{B}_{2(\text{g})}\rightleftharpoons\text{X}_{2(\text{g})},\triangle_\text{r}\text{H}=-\text{XkJ}?$
- Low temperature and high pressure.
- Low temperature and low pressure.
- High temperature and high pressure.
- High temperature and low pressure.
- For the reversible reaction,
$\text{N}_{2(\text{g})}+3\text{H}_{2(\text{g})}\rightleftharpoons2\text{NH}_{3(\text{g})}+\text{heat}$
The equilibrium shifts in forwarding direction
- By increasing the concentration of NH3(g)
- By decreasing the pressure.
- By decreasing the concentrations of N2(g) and H2(g)
- By increasing pressure and decreasing temperature.
- In which one of the following equilibria will the point of equilibrium shift to left when the pressure of the system is increased?
- $\text{H}_{2(\text{g})}+\text{l}_{2(\text{g})}\rightleftharpoons2\text{HI}_{(\text{g})}$
- $2\text{NH}_{3(\text{g})}\rightleftharpoons\text{N}_{2(\text{g})}+3\text{H}_{2(\text{g})}$
- $\text{C}_{(\text{s})}+\text{O}_{2(\text{g})}\rightleftharpoons\text{CO}_{2{\text{g}}}$
- $2\text{H}_{2(\text{g})}+\text{O}_{2(\text{g})}\rightleftharpoons2\text{H}_2\text{O}_{(\text{g})}$
The molecular orbital theory is based on the principle of a linear combination of atomic orbitals. According to this approach when atomic orbitals of the atoms come closer, they undergo constructive interference as well as destructive interference giving molecular orbitals, i.e., two atomic orbitals overlap to form two molecular orbitals, one of which lies at a lower energy level (bonding molecular orbital). Each molecular orbital can hold one or two electrons in accordance with Pauli's exclusion principle and Hund's rule of maximum multiplicity.
For molecules up to $N _2$, the order of filling of orbitals is:
Bond order $=\frac{1}{2}$ [bonding electrons - antibonding electrons]
Bond order gives the following information:
I. If bond order is greater than zero, the molecule/ion exists otherwise not.
II. Higher the bond order, higher is the bond dissociation energy.
III. Higher the bond order, greater is the bond stability.
IV. Higher the bond order, shorter is the bond length.
1. Arrange the following negative stabilities of $CN , CN ^{+}$and $CN ^{-}$in increasing order of bond. (1)
2. The molecular orbital theory is preferred over valence bond theory. Why? (1)
3. Ethyne is acidic in nature in comparison to ethene and ethane. Why is it so? (2)
OR
Bonding molecular orbital is lowered by a greater amount of energy than the amount by which antibonding molecular orbital is raised. Is this statement correct? (2)
→For molecules up to $N _2$, the order of filling of orbitals is:
Bond order $=\frac{1}{2}$ [bonding electrons - antibonding electrons]
Bond order gives the following information:
I. If bond order is greater than zero, the molecule/ion exists otherwise not.
II. Higher the bond order, higher is the bond dissociation energy.
III. Higher the bond order, greater is the bond stability.
IV. Higher the bond order, shorter is the bond length.
1. Arrange the following negative stabilities of $CN , CN ^{+}$and $CN ^{-}$in increasing order of bond. (1)
2. The molecular orbital theory is preferred over valence bond theory. Why? (1)
3. Ethyne is acidic in nature in comparison to ethene and ethane. Why is it so? (2)
OR
Bonding molecular orbital is lowered by a greater amount of energy than the amount by which antibonding molecular orbital is raised. Is this statement correct? (2)
The ionic character of metallic halides tends toward covalent nature as per Fajan's rule. Such covalent halides behave as non-metal in their higher oxidation states. The property to hydrolyse to give oxy-acids of the element and corresponding hydro halogen acid for most non-metallic elements proceeds exceptionally in the way, keeping oxidation number of element and halide sam in oxo-acids.
Non-polar halides are immiscible in water, as they do not show hydrolysis, but halides of some elements with empty d-orbital undergo hydrolysis. Stability of halides of the higher state is governed by the inert-pair effect.
1. How does halide undergo hydrolysis to give oxy-acids of underlined element $PCl _3$ ? (1)
2. Out of $NCl _3$ and $BCl _3$ undergoes hydrolysis to form oxy-acids? Write the chemical reaction for the correct answer. (1)
3. Out of $PbCl _4, PbF _4, PbI _4$ and $PbBr _4$ which one doesn't exist? (2)
OR
Non-Polar halides are immiscible in water. Why? (2)
→→→Non-polar halides are immiscible in water, as they do not show hydrolysis, but halides of some elements with empty d-orbital undergo hydrolysis. Stability of halides of the higher state is governed by the inert-pair effect.
1. How does halide undergo hydrolysis to give oxy-acids of underlined element $PCl _3$ ? (1)
2. Out of $NCl _3$ and $BCl _3$ undergoes hydrolysis to form oxy-acids? Write the chemical reaction for the correct answer. (1)
3. Out of $PbCl _4, PbF _4, PbI _4$ and $PbBr _4$ which one doesn't exist? (2)
OR
Non-Polar halides are immiscible in water. Why? (2)
Once an organic compound is extracted from a natural source or synthesised in the laboratory, it is essential to purify it. Various methods used for the purification of organic compounds are based on the nature of the compound and the impurity present in it. Finally, the purity of a compound is ascertained by determining its melting or boiling point. This is one of the most commonly used techniques for the purification of solid organic compounds. In crystallisation Impurities, which impart colour to the solution are removed by adsorbing over activated charcoal. In distillation Liquids having different boiling points vaporise at different temperatures. The vapours are cooled and the liquids so formed are collected separately. Steam Distillation is applied to separate substances which are steam volatile and are immiscible with water. Distillation under reduced pressure: This method is used to purify liquids having very high boiling points.
1. Which method can be used to separate two compounds with different solubilities in a solvent?
OR
Why chloroform and aniline are easily separated by the technique of distillation?
2. Distillation method is used to separate which type of substance?
3. Which technique is used to separate aniline from aniline water mixture?
1. Which method can be used to separate two compounds with different solubilities in a solvent?
OR
Why chloroform and aniline are easily separated by the technique of distillation?
2. Distillation method is used to separate which type of substance?
3. Which technique is used to separate aniline from aniline water mixture?
Read the passage given below and answer the following questions from 1 to 5. Chemistry deals with varieties of matter and change of one kind of matter into the other. Transformation of matter from one kind into another occurs through the various types of reactions. One important category of such reactions is Redox Reactions. Originally, the term oxidation was used to describe the addition of oxygen to an element or a compound. Because of the presence of dioxygen in the atmosphere (~20%), many elements combine with it and this is the principal reason why they commonly occur on the earth in the form of their oxides. The following reactions represent oxidation processes: $2\text{Mg}(\text{s})\rightarrow2\text{MgO}\text{ (S)}$ $\text{S}(\text{s})+\text{O}_2(\text{g})\rightarrow\text{SO}_2\text{ g}$ the term “oxidation” is defined as the addition of oxygen/electronegative element to a substance or removal of hydrogen/ electropositive element from a substance. In the beginning, reduction was considered as removal of oxygen from a compound. However, the term reduction has been broadened these days to include removal of oxygen/electronegative element from a substance or addition of hydrogen/ electropositive element to a substance. According to the definition given above, the following are the examples of reduction processes: $2\text{HgO}\text{S}\xrightarrow{\triangle}2\text{ Hg}(1)+\text{O}_2(\text{g})$ $2\text{HgCl}_2(\text{aq})+\text{SnCl}_2(\text{aq})\rightarrow\text{Hg}_2\text{Cl}_2(\text{s})+\text{SnCl}_4(\text{aq})$ In reaction simultaneous oxidation of stannous chloride to stannic chloride is also occurring because of the addition of electronegative element chlorine to it. It was soon realised that oxidation and reduction always occur simultaneously (as will be apparent by re-examining all the equations given above), hence, the word “redox” was coined for this class of chemical reactions. 
For convenience, each of the above processes can be considered as two separate steps, one involving the loss of electrons and the other the gain of electrons. As an illustration, we may further elaborate one of these, say, the formation of sodium chloride. $2\text{Na}(\text{s})\rightarrow2\text{Na}^+\text{g}+2\bar{\text{e}}$ $\text{Cl}_2\text{g}+2\bar{\text{e}}\rightarrow2\text{C}\bar{\text{I}}\text{ (g)}$ Each of the above steps is called a half reaction, which explicitly shows involvement of electrons. Sum of the half reactions gives the overall reaction $2\text{Na}(\text{s})+\text{Cl}_2\text{(g)}\rightarrow2\text{Na}^+\text{CI}(\text{s})\text{ or } 2\text{NaCI}(\text{s})$ Above Reactions suggest that half reactions that involve loss of electrons are called oxidation reactions. Similarly, the half reactions that involve gain of electrons are called reduction reactions. To summarise, we may mention that Oxidation: Loss of electron(s) by any species. Reduction: Gain of electron(s) by any species. Oxidising agent: Acceptor of electron(s). Reducing agent: Donor of electron(s).
→The reactions:
$2\text{Na}(\text{s})+\text{Cl2}\text{g}\rightarrow2\text{NaCl}(\text{s})$ $4\text{Na}(\text{s})+\text{O}_2\text{g}\rightarrow2\text{Na}_2\text{o}(\text{s})$ $2\text{Na}(\text{s})+\text{S}\text{(s)}\rightarrow2\text{Na}_2\text{S}(\text{s})$ are redox reactions because in each of these reactions sodium is oxidised due to the addition of either oxygen or more electronegative element to sodium. Simultaneously, chlorine, oxygen and sulphur are reduced because to each of these, the electropositive element sodium has been added. From our knowledge of chemical bonding we also know that sodium chloride, sodium oxide and sodium sulphide are ionic compounds and perhaps better written as Na+ Cl–(s), (Na+)2 O2–(s), and (Na+)2 S2 –(s). Development of charges on the species produced suggests us to rewrite the reactions in the following manner: For convenience, each of the above processes can be considered as two separate steps, one involving the loss of electrons and the other the gain of electrons. As an illustration, we may further elaborate one of these, say, the formation of sodium chloride. $2\text{Na}(\text{s})\rightarrow2\text{Na}^+\text{g}+2\bar{\text{e}}$ $\text{Cl}_2\text{g}+2\bar{\text{e}}\rightarrow2\text{C}\bar{\text{I}}\text{ (g)}$ Each of the above steps is called a half reaction, which explicitly shows involvement of electrons. Sum of the half reactions gives the overall reaction $2\text{Na}(\text{s})+\text{Cl}_2\text{(g)}\rightarrow2\text{Na}^+\text{CI}(\text{s})\text{ or } 2\text{NaCI}(\text{s})$ Above Reactions suggest that half reactions that involve loss of electrons are called oxidation reactions. Similarly, the half reactions that involve gain of electrons are called reduction reactions. To summarise, we may mention that Oxidation: Loss of electron(s) by any species. Reduction: Gain of electron(s) by any species. Oxidising agent: Acceptor of electron(s). Reducing agent: Donor of electron(s). - Addition of electronegative element to a substance is known as..
- Oxidation
- Reduction
- Redox reaction
- All the above
- Removal of electronegative element to a substance is known as ..
- Oxidation
- Reduction
- Redox reaction
- All the above
- Acceptor of electrons is …
- Reducing Agent
- Catalytic Agent
- Oxidising Agent
- None of above
- Donor of electrons is…
- Organic Agent
- Catalytic Agent
- Oxidising Agent
- Reducing Agent
- Oxidation and Reduction occurs simultaneously is known as …
- Exothermic reaction
- Endothermic reaction
- Redox reaction
- Neutralization reaction