Recent questions tagged sec-c

(a) Give the equation of reaction for the preparation of phenol from cumene. (b) Write the chemical reaction for the preparation of phenol from chloro benzene

asked Nov 11, 2016 by meena.p

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Explain why inspite of nearly the same electronegativity , oxygen forms hydrogen bonding while chloride does not

asked Nov 11, 2016 by meena.p

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State the reason in each of the following cases: (i) Soaps do not work well in hard water (ii) Synthetic detergents are better than soaps .

asked Nov 10, 2016 by meena.p

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Distinguish between rate expression and rate constant of a reaction

asked Nov 10, 2016 by meena.p

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Calculate the amount of KCl which must be added to $1\;kg$ of water so that the freezing point is depressed by $2\;k$? ($k_f$ for water = $1.86 \;K \;mol^{-1}$)

asked Nov 10, 2016 by meena.p

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a)Give chemical tests to distinguish between compounds in each of the following pairs: i) Benzaldehyde and Acetone ii)Phenol and Ethanol b)Give reasons for the following: i)Although –$NH_2$ group is an ortho and para directing group, nitration of aniline gives along with ortho and para as well as meta derivative also, why? ii)Conc.HI is preferable used in the cleavage of ether linkage. Explain. iii)Out of $PCl_5$ and $SOCl_2$ which one is a better reagent for the conversion of alcohol to alkyl chloride and why?

asked Nov 10, 2016 by meena.p

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How would you account for the following : (i) The following order of increase in strength of acids $PH_3 < H_2S < HCl $ (ii) The oxidizing power of oxo-acids of chlorine follows the order . $HClO_4 < HClO_3 < HClO_2 < HClO$

asked Nov 9, 2016 by meena.p

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a)What are polysaccharides ? Give one example b)Give the preparation and uses of PVC

asked Nov 8, 2016 by meena.p

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Answer the following questions : (i) Why do soaps not work in hard water. (ii) What are the main constituents of dettol (iii) How do antiseptic differ from disinfectants

asked Nov 8, 2016 by meena.p

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How do you explain the presence of an aldehydic group in a glucose molecule ?

asked Nov 7, 2016 by meena.p

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Show how will you synthesize : (i) 1- phenylethanol from a suitable alkene (ii) cyclohexyl methanol using an alkyl halide by an $SN^2$ reaction . (iii) Pentan-1-ol using a suitable alkyl halide ?

asked Nov 7, 2016 by meena.p

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p- Dichlorobenzene has higher melting point and lower solubility than o- and m- isomers Discuss.

asked Nov 7, 2016 by meena.p

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A solution of $KMnO_4$ on reducing yields either a colourless solution or a brown precipitate or a green solution depending on $PH$ of the solution . What different stages of the reduction do these represent and how are they carried out ?

asked Nov 7, 2016 by meena.p

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Why are pentahalides more covalent than trihalides ?

asked Nov 7, 2016 by meena.p

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Why is it advantageous to roast a sulphide ore to the oxide before reduction ?

asked Nov 7, 2016 by meena.p

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How do size of particles of absorbent , pressure of gas and prevailing temperature enfluence the extent of absorption of a gas on a solid ?

asked Nov 7, 2016 by meena.p

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Differenciate between rate of reaction and reaction rate constant

asked Nov 4, 2016 by meena.p

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Depict the galvanic cell in which the reaction $2Zn(s) +2 Ag^{+}(aq) \to Zn ^{2+}(aq) +2 Ag(s) $ takes place . Further show: (i) Which of the electrode is negatively charged? (ii) The carriers of the current in the cell. (iii) Individual reaction at each electrode.

asked Nov 4, 2016 by meena.p

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Why is boiling point of water increased on addition of sodium chloride into it ?

asked Nov 4, 2016 by meena.p

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Explain why does conductivity of germanium crystals increase on doping with gallium

asked Nov 4, 2016 by meena.p

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When $1 \;mol$ of $NaCl$ is added to 1 litre of water , the boiling point of water increases on other hand, addition of 1mol of methyl alcohol to one litre of water decreases the boiling point of water . Explain why does this happen .

asked Nov 4, 2016 by meena.p

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Low density polythene and high density polythene , both are polymers of ethene but there is marked difference in their properties . Explain

asked Nov 4, 2016 by meena.p

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How do antiseptics differ from disinfectant? Give one example of each case

asked Nov 4, 2016 by meena.p

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Differentiate between chiral and achiral molecules :

asked Nov 3, 2016 by meena.p

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$CuSO_4.5H_2O$ is blue in colour while $CuSO_4$ is colourless . why ?

asked Nov 3, 2016 by meena.p

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Why do the d-block elements exhibits a large number of oxidation states than f - block elements

asked Nov 3, 2016 by meena.p

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When Cons $H_2SO_4$ was added into an unknown salt present in a test tube, a brown gas (A) was evolved . This gas intensified when copper turnings were also added into this test tube . On cooling , the gas (A) changed into a colourless gas (B) (a) identify the gases A and B.

asked Nov 3, 2016 by meena.p

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With the help of an example how one can separate two sulphide ores by froth flotation method .

asked Nov 3, 2016 by meena.p

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Explain what is observed when (a) an electric current is passed through a solution . (b) a beam of light is passed through a solution (c) an electrolyte (say NaCl) is added to ferric hydroxide solution .

asked Nov 3, 2016 by meena.p

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For the reaction $A \to B$ ,the rate of reaction becomes twenty seven times when the concentration of A is increased three times . What is the order of the reaction ?

asked Nov 3, 2016 by meena.p

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What would happen if no salt bridge were used in an electro chemical cell (like Zn-Cu cell)?

asked Nov 3, 2016 by meena.p

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If the solubility product of $CuS$ is $ 6 \times 10^{-6}$ calculate the maximum molarity of $CuS$ is aqueous solution

asked Nov 2, 2016 by meena.p

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What is the scientific explaination for the feeling of depression ?

asked Nov 2, 2016 by meena.p

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How would you account for the following ? (i) Many of the transition elements are known to form interstitial compounds . (ii) The metallic radii of the third (5d) series of transition metals are virtually the same as those of the corresponding group members of the second (4d) series .(iii) Lanthanoids form primary +3 ions , while the actinoids usually have higher oxidation state in their compounds , +4 or even +6 typical .

asked Nov 1, 2016 by meena.p

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a)Draw the structure of A- methylpent -3-en-2-one b) Write the structure of 4 - methyl pent -3-en -2- one

asked Nov 1, 2016 by meena.p

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(a) What is the role of benzoyl peroxide in polymerization of ethane ? (b) What are LDPE and HDPE ? How are they prepared?

asked Oct 31, 2016 by meena.p

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What are common types of secondary structure of proteins ?

asked Oct 31, 2016 by meena.p

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State the uses of carboxylic acids :

asked Oct 31, 2016 by meena.p

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Explain why phenols do not undergo substitution of the -OH group like alcohols ?

asked Oct 31, 2016 by meena.p

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What happens when bromine reacts with $CH_3 - C = CH$? How would you justify this reaction ?

asked Oct 27, 2016 by meena.p

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(i) Why do compounds having similar geometry have different magnetic moment ? (ii)$FeSO_4$ solution mixed with $(NH_4)_2SO_4$ solution in 1 : 1 molar ratio gives the test of $Fe^{2+}$ ion but $CuSO_4$ solution mixed with aqueous ammonia in 1 : 4 molar ratio does not give the test of $Cu^{2+}$ ion. Explain why ?

asked Oct 27, 2016 by meena.p

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Give the reasons for the following : (a) $CN^{-}$ ions is known but $CP^{-} $ ion is not known (b) $NO_2$ dimerizes to form $N_2O_4$ (c) $ICI$ is more reactive that $I_2$

asked Oct 27, 2016 by meena.p

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Out of C and CO, which is a better reducing agent for ZnO ?

asked Oct 27, 2016 by meena.p

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Nitric oxide $NO,$ reacts with oxygen to produce nitrogen dioxide $2 NO(g)+O_2(g) \to 2NO_2(g)$ The rate law for this reaction is : $Rate = k[NO]^2 [O_2]$ Propose a mechanism for the reaction.

asked Oct 27, 2016 by meena.p

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Account for the following : (i) Alkaline medium inhibits rusting of iron . (ii) Iron does not rust even if the zinc coating is broken in a galvanized iron pipe.

asked Oct 27, 2016 by meena.p

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Why a person suffering from high blood pressure is advised to take minimum quantity of common salt

asked Oct 26, 2016 by meena.p

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If the radius of the octahedral void is r and the radius of the atoms in the close packing is R, derive relationship between r and R.

asked Oct 26, 2016 by meena.p

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Although chlorine is an electron with drawing group , yet it is ortho- , Para - directing in electrophilic aromatic substitution reaction . Explain why it is so ?

asked Oct 26, 2016 by meena.p

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Resistance of a conductivity cell filled with $0.1\;mol L^{-1}KCl$ solution is $100\;\Omega$ . If the resistance of the same cell when filled with $0.02\;molL^{-1}\;KCl$ Solution . The conductivity of $0.02\;mol L^{-1}KCl$ Solution . The conductivity of $0.1\;mol\;L^{-1}$ Solution is $1.29\;s/m$

asked Oct 26, 2016 by meena.p

1 answer

Why does a galvanic cell become dead after some time ?

asked Oct 25, 2016 by meena.p

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