Description : What are alkanes? Why are they called paraffins?
Last Answer : Ans. Those hydrocarbons which contain single bond between carbon- carbon are called alkanes. They are called paraffins because they are very less reactive (Latin- Parum= little, affins = affinity)
Description : Arrange the following in order of decreasing reactivity towards alkanes. HCl, HBr, HI, HF
Last Answer : Ans. HI> HBr> HCl >HF
Description : Explain why Grignard reagents do not reacts with alkanes.
Last Answer : Ans. In alkanes , the C – H bond has very little polarity . The hydrogen cannot be abstracted by the Grignard reagent.
Description : Why are alkanes called paraffins?
Last Answer : Paraffin’s means little affinity; alkanes due to strong C-C and C-H bonds are relatively chemically inert.
Description : How will you demonstrate that double bonds of benzene are somewhat different from that of olefins?
Last Answer : Ans. The double bonds of olefins decolorize bromine water and discharge the pink colour of Bayer‘s reagent while those of benzene not.
Description : Explain the physical properties of benzene and its homologues.
Last Answer : Ans: i. Benzene and its homologous upto eight carbon atoms are colourless liquids with characteristic smell. ii. Aromatic hydrocarbons are immiscible with water but soluble in organic solvents. iii. ... compounds increases with increase in molecular mass due to increase in van der waals forces.
Description : Out of benzene, m–dinitrobenzene and toluene which will undergo nitration most easily and why?
Last Answer : Ans. -CH3 group is electron donating while –NO2 group is electron withdrawing. Therefore, maximum electron density will be in toluene , followed by benzene and at least in m-dinitrobenzene. Therefore, the ease of nitration decreases in the order: Toluene> benzene> m-dinitrobenzene
Description : Which one is more stable structure of benzene among Kekule and Dewar’s structures?
Last Answer : Ans: Kekule’s structure.
Description : Define benzenoids Compounds.
Last Answer : Ans: Aromatic compounds containing benzene ring.
Description : Define Aromatic Compounds.
Last Answer : Ans: The Compounds which gives pleasant smell.
Description : How will you separate propene from propyne?
Last Answer : Ans. By passing the mixture through ammonical silver nitrate solution when propyne reacts while propene passes over.
Description : What is Grignard reagent?
Last Answer : Ans. Alkyl magnesium halides
Description : What is meant by restricted rotation around of carbon-carbon double bond? What type of isomerism does it lead to?
Last Answer : Ans. The carbon-carbon double bond in alkene contains one sigma bond and one pi-bond. The Pibond involves the overlapping of unhybridised p orbital of two carbon atom .The rotation around the ... , the free rotation around C=C double bond is restricted, which gives rise to Geometrical Isomerism.
Description : How will you detect the presence of unsaturation in an organic compound?
Last Answer : Ans. Generally Unsaturated organic compound decolorize Bayer‘s reagent and Bromine water.
Description : Name two reagents which can be used to distinguish between ethene and ethyne.
Last Answer : Ans. Tollen‘s reagent
Description : Out of ethylene and acetylene which is more acidic and why?
Last Answer : Ans. Acetylene, due to greater electonegativity of the sp hybridised carbon.
Description : Arrange the following in the increasing order of C-C bond length- C2H6 , C2H4, C2H2
Last Answer : Ans. C2H2 < C2H4 < C2H6
Description : What effect does branching of an alkane chain has on its boiling point?
Last Answer : Ans. As branching increases, the surface area of the molecule decreases which results in a small area of contact. As a result, the Van der Waals force also decreases which can be overcome at ... lower temperature. Hence, the boiling point of an alkane chain decreases with an increase in branching.
Description : What are the necessary conditions for any system to be aromatic?
Last Answer : Ans. A compound is said to be aromatic if it satisfies the following three conditions: (i) It should have a planar structure. (ii) The π-electrons of the compound are completely delocalized in the ring. (iii)The total number ... to (4n + 2), where n = 0, 1, 2 etc. This is known as Huckel s rule.
Description : What are the main constituent of LPG?
Last Answer : Ans. Butane and isobutane . Both these isomers can be easily liquified and hence can be conveniently transported in iron cylinder.
Description : Is it possible to isolate pure staggered ethane or pure eclipsed ethane at room temperature? Explain .
Last Answer : The energy differences between staggered and eclipsed forms of ethane is just 12.55 kj mol_1 which is easily met by collisions of the molecules at room temperature. Therefore, it is not possible to isolate either pure staggered or pure eclipsed ethane at room temperature.
Description : Which of the following has highest boiling point and why?(L-II) (a) 2 methylpentane (b) 2,3 dimethyl butane (c) 2,2 dimythylbutane
Last Answer : Ans. As the branching increases, surface area decreases. As a result, magnitude of Vander Waals forces of attraction decreases and hence the boiling point decreases. Thus, the overall order of decreasing boiling point is: 2 methylpentane (333k) > 2,3 dimethylbutane (331k) > 2,2 dimethylbutane(323k)
Description : (a) What effect the branching of an alkane has on its melting point? (L-III) (b) Which of the following has highest boiling point?(L-III) (1) 2-methyl pentane. (2) 2, 3-diethyl butane. (3) 2, 2- dimethyl butane.
Last Answer : Ans.(a) In general conception, as the branching increases packing of the molecules in the crystals becomes less close and have melting point decreases accordingly. (b) As the branching increases, ... attraction decreases and hence the boiling point decreases. So, 2-methyl pentane has highest B.pt.
Description : Arrange the three isomers of pentane in increasing order of their boiling points?
Last Answer : Ans.2, 2-Dimethylpropane
Description : What do you mean by pyrolysis?
Last Answer : The decomposition of a compound by the heat is called pyrolysis. This process when applied to alkanes is known as cracking.
Description : What are conformations?
Last Answer : Conformations are spatial arrangements which are obtained by rotation around sigma bonds.
Description : The thermal decomposition of alkanes in the absence of air is called : (a) Combustion (b) Oxidation (c) Cracking (d) Hydrogenation
Last Answer : Cracking
Description : A family of organic compounds containing only carb and hydrogen and having only single bonds are the: w) alkenes and alkanes x) alkanes and cycloalkanes y) alkynes (pron: AL-kines) and alkenes z) cycloalkanes and alkenes
Last Answer : ANSWER: B -- ALKANES AND CYCLOALKANES
Description : A detective who was mere days away from cracking an international oil smuggling ring has suddenly gone missing. While inspecting his last-known location, officers find a note: 710 57735 34 5508 51 7718. ... , and Todd. Can you break the detective's code and find the criminal's name? -Riddles
Last Answer : Bill is the suspect if you read upside down the numbers it says: 'Bill is boss. He sells oil.
Description : Explain why the water molecule has a bent shape and a bond angle less than 109.5° The electron repulsion between the two lone pairs of electrons on the oxygen of water causes the O–H bonds to squeeze close together
Last Answer : The electron repulsion between the two lone pairs of electrons on the oxygen of water causes the O–H bonds to squeeze close together
Description : Which statements about alkenes and alkanes of corresponding chain lengths is true? (I) Alkenes have slightly lower melting points than alkanes (II) Alkenes have slightly higher melting points than alkanes (III) Alkenes have higher boiling ... (a) I and III (b) II and IV (c) I and IV (d) II and III
Last Answer : I and III
Description : Which statement is false? (a) Many alkanes are soluble in water. (b) All alkanes have a lower density than water. (c) At room temperature some alkanes are liquids, some solids, some gases. (d) All alkanes burn
Last Answer : Many alkanes are soluble in water
Description : Is the bond energy of all the four C-H bonds in CH4 molecule equal? If not then why ? How is C-H bond energy then reported?
Last Answer : Ans. No because after breaking of C-H bonds one by one, the electronic environments change. The reported value is the average of of the bond dissociation energies of the four C-H bonds.
Description : Which group forms the strongest H-bonds to water molecules? (a) Alcohols (b) Ethers (c) Phenols (d) All equally strong
Last Answer : Phenols
Description : What property of low-molecular weight aldehydes and ketones accounts for the magnitude of their boiling points? (a) The ability to form strong H-bonds between their molecules. (b) The ability of ... other polar molecules. (d) The ability of the carbonyl group to attract electrophiles and form bonds.
Last Answer : The ability of the polar carbonyl group to attract other polar molecules.
Description : Which of the bonds in Ethyl alcohol (CH3CH2OH) will undergo heterolytic bond fission most readily? (a) O–H (b) C–H (c) C–O (d) C–C
Last Answer : O–H
Description : Which of the following statements is not true about propyne, HC–C≡CH3? (a) It contains six sigma bonds. (b) It contains three pi bonds. (c) The H–C–H bond angle is about 109.5°. (d) The C–C–C bond angle is 180°.
Last Answer : It contains three pi bonds
Description : Which of the following statements about ethene, C2H4, is incorrect? (a) The H–C–H bond angles are approximately 109.5°. (b) There is a total of five sigma bonds. (c) The carbon atoms are sp2 hybridized. (d) The H–C–H bond angles are approximately 120°.
Last Answer : The H–C–H bond angles are approximately 109.5°.
Description : Saturated hydrocarbons are called - (1) Alkynes (2) Alkenes (3) Alkanes (4) All of the above
Last Answer : (3) Alkanes Explanation: Carbon compounds which contain just carbon and hydrogen are called hydrocarbons. Among these, the saturated hydrocarbons are called alkanes. The unsaturated hydrocarbons which contain one or more double bonds are called alkenes.
Description : What is the hybridization of carbon atoms in alkanes ?
Last Answer : Ans. Sp3
Description : Cycloalkanes have the same molecular formula as : (a) Alkanes (b) Alkenes (c) Alkynes (d) Cycloalkenes
Last Answer : Alkenes
Description : Ninhydrin test is given by (a) Carbohydrates (b) Proteins (c) Alkanes (d) Alkenes
Last Answer : Proteins
Description : The high boiling points of alcohols, as compared to the corresponding alkanes, are due to (a) Hydrogen bonding (b) Heavy oxygen atom (c) Water solubility (d) None of these
Last Answer : Hydrogen bonding
Description : Which of the following methods can be used to increase the octane rating of gasoline? (a) Adding branched-chain alkanes (b) Adding tetraethyllead (c) Adding aromatic hydrocarbons (d) All of these
Last Answer : All of these
Description : Consider the three isomeric alkanes n-hexane, 2,3-dimethylbutane, and 2- methylpentane. Which of the following correctly lists these compounds in order of increasing boiling point? (a) 2,3-dimethylbutane < 2- ... < 2, 3-dimethylbutane < n-hexane (d) n-hexane < 2-methylpentane < 2,3-dimethylbutane
Last Answer : 2,3-dimethylbutane < 2-methylpentane < n-hexane
Description : In the chlorination of alkanes, the first step in which chlorine free radicals are produced is called : (a) initiation (b) activation (c) propagation (d) deactivation
Last Answer : initiation
Description : Why is the halogenation of alkanes considered a chain reaction? (a) it occurs quickly. (b) it occurs without the generation of intermediates. (c) each step generates the reactive intermediate that causes the next step to occur. (d) the reaction allows long chains of halogenated alkanes to be formed
Last Answer : each step generates the reactive intermediate that causes the next step to occur
Description : Which of the following classes of compounds is unreactive toward sulfuric acid? (a) Alkanes (b) Alcohols (c) Alkenes (d) Alkynes
Last Answer : Alkanes
Description : Which of the following reactions can be used to prepare alkanes? (a) Wurtz reaction (b) Wolf-kishner reduction (c) Kolbe's electrolysis (d) All of these
Description : Which of the following reactions can be used to prepare alkanes? (a) Corey-House synthesis (b) Williamson synthesis (c) Friedel-Crafts reactions (d) None of these
Last Answer : Corey-House synthesis