Recent questions tagged class11

Ketanol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol. The enol and keto fprms are said to be tatutomers of each other. The interconversion of the two forms involved the movements of a proton and the shifting of bonding electrons. A compound containing a carbonyl group $(C=0)$ is normally in rapid equilibrium with an enol tautomer, which contains a pair of doubly bonded carbon atoms adjacent to a hydroxyl $(-OH)$ group, $C=C-OH$ For a carbonyl compound to exhibit tautomerism, the essential condition is that, it must have at least one $ \alpha -H$ atom. Generally , the keto form is more stable than the enol form due to the greater strength of the carbon- oxygen $\pi$ bond as compared - carbon $\pi$ bond. In keto-enol tautomerism of dicarbonyl compounds, the enol form is preferred in contrast to the keto- form , this is due to

asked Feb 26, 2014 by meena.p

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Heat of neutralisation of HCl with $NH_4OH$ and NaOH with $CH_3COOH$ are respectively -51.4 and -50.6 kJ $eq^{-1}$. What will be the heat of neutralisation of acetic acid with $NH_4OH$?

asked Feb 26, 2014 by mosymeow_1

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If the heat of neutralisation for a strong acid-base reaction is -57.1 kJ what would be the heat released when 350 $cm^3$ of 0.20 M $H_2SO_4$ is mixed with 650 $cm^3$ of $0.10\; M\; NaOH$ ?

asked Feb 26, 2014 by mosymeow_1

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How many terms of the G.P. $3,3^2,3^3.......$ are needed to give the sum $120$?

asked Feb 26, 2014 by rvidyagovindarajan_1

1 answer

The disintegration rate of a radioactive sample at a certain instant is 4750 dpm . Five minute later rate becomes 2700 disintegration per minute . Then the decay constant is

asked Feb 26, 2014 by yamini.v

2 answers

The sum of first $3$ terms of a G.P is $\large\frac{39}{10}$ and their product is $1$. Find the common ratio and the terms of the G.P.

asked Feb 26, 2014 by rvidyagovindarajan_1

1 answer

Evaluate $\sum\limits_{k=1}^{11} (2+3^k)$

asked Feb 26, 2014 by rvidyagovindarajan_1

1 answer

The stability of carbanions in the following :

asked Feb 26, 2014 by meena.p

1 answer

The most unlikely representation of resonance structure of P-nitrophenoxide ion is

asked Feb 26, 2014 by meena.p

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If the bond dissociation energies of the diatomic molecules $XY, X_2$ and $Y_2$ are in the ratio of 1 : 1 : 0.5 and $\Delta_fH$ for the formation of XY is -200 kJ $mol^{-1}$. What is the bond dissociation energy of $X_2$ will be

asked Feb 26, 2014 by mosymeow_1

1 answer

Find the sum of $n$ terms of the G,P, $x^2,x^4,x^6...........$ in terms of $x$

asked Feb 26, 2014 by rvidyagovindarajan_1

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Find the sum up to $n$ terms of the G.P. $1,-a,a^2,-a^3.........$

asked Feb 26, 2014 by rvidyagovindarajan_1

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Increasing order of stability among the three main conformation (ie eclipse, anti, gauche) of 2- fluoroethanol is

asked Feb 26, 2014 by meena.p

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Find the sum upto $n$ terms of the G.P. $\sqrt 7,\sqrt {21},3\sqrt 7,.......$

asked Feb 26, 2014 by rvidyagovindarajan_1

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For $(i) I^-, (ii) Cl^{-}, (iii) Br^{-} $. The increasing order of nuclephilicity would be :

asked Feb 26, 2014 by meena.p

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Which of the following is the correct order of decreasing $SN_2$ reactivity :

asked Feb 26, 2014 by meena.p

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The order of decreasing stability of the carbanions $(CH_3)_3 C^-(I) ; (CH_3)_2CH^{-1}(II) ; CH_3CH_2^{-}(III); C_6H_5CH_2^{-} (IV)$ is

asked Feb 26, 2014 by meena.p

1 answer

If two compounds have same empirical formula but different molecular formulae, they must have,

asked Feb 26, 2014 by meena.p

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Which of the following conformations cyclohexane is chiral?

asked Feb 26, 2014 by meena.p

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Which of the following alkenes will react fastest with $H_2$ under catalytic hydrogenation conditions ?

asked Feb 26, 2014 by meena.p

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Which of the following compounds possesses the $C-H$ bond with the lowest bond dissocation energy :

asked Feb 26, 2014 by meena.p

1 answer

$N_2 + 3H_2 \longrightarrow 2NH_3$ This reaction is carried out at constant temperature and pressure. If $\Delta H$ and $\Delta U$ are enthalpy and internal energy change for the reaction, which of the following expression is true?

asked Feb 26, 2014 by mosymeow_1

1 answer

Toutomerism is not exhibited by

asked Feb 26, 2014 by meena.p

1 answer

For a spontaneous reaction, the $\Delta G$, equilibrium constant, K and $E^\circ _{cell}$ will be respectively

asked Feb 26, 2014 by mosymeow_1

1 answer

$MgO(s) + 2HCl(aq) \longrightarrow MgCl_2(aq) + H_2O(l)$; The absolute enthalpy of neutralisation of the reaction is

asked Feb 26, 2014 by mosymeow_1

1 answer

How much heat would release when an aqueous solution containing 0.5 mol of $HNO_3$ is mixed with 0.3 mol of $OH^{-1}$? Given, enthalpy of neutralisation is -57.1 kJ.

asked Feb 26, 2014 by mosymeow_1

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At 1 atm pressure, for a reaction $\Delta H = + 30.558$ kJ $mol^{-1}$ and $\Delta S = 0.066$ kJ $mol^{-1}$. The temperature at which free energy is equal to zero and the nature of the reaction below this temperature are

asked Feb 26, 2014 by mosymeow_1

1 answer

The compound , whose stereo-chemical formula is written below exhibits x geometrical isomers and y optical isomers.

asked Feb 26, 2014 by meena.p

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Study the following table and, on the basis of these values of $\Delta H$ and $\Delta S$ for five different reactions, predict which one of these will be spontaneous at all temperatures?

asked Feb 26, 2014 by mosymeow_1

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A cylinder of gas is assumed to contain 14 kg of butane. A normal family requires 20,000 kJ of energy per day for cooking. How many days will the butane gas in the cylinder last?

asked Feb 26, 2014 by mosymeow_1

1 answer

Out of the following , the one containing only nucleophiles is

asked Feb 26, 2014 by meena.p

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What is the change in entropy of 1 mole of a perfect gas, which expands isothermally to ten times its original volume?

asked Feb 26, 2014 by mosymeow_1

1 answer

Which of the following rings in most strained ?

asked Feb 26, 2014 by meena.p

1 answer

The total number of carboxylic acid groups in the product P is :

asked Feb 26, 2014 by meena.p

1 answer

The heat liberated when 50 $cm^3$ of 0.2 N $H_2SO_4$ is mixed with 50 $cm^3$ of 1 N KOH, is

asked Feb 25, 2014 by mosymeow_1

1 answer

Show the relation between the enthalpies of the reactions: $H_2(g)+ \frac{1}{2} O_2(g) \rightarrow H_2O(g); \Delta H_1$ and $H_2(g)+\frac{1}{2}O_2(g) \rightarrow H_2O(l); \Delta H_2$

asked Feb 25, 2014 by mosymeow_1

1 answer

What is the standard Gibbs energy change for the reaction at 298 K, if standard enthalpy and standard entropy changes for the oxidation of ammonia at 298 K are 382.64 kJ $mol^{-1}$ and -145.6 $JK^{-1}mol^{-1}$, respectively.

asked Feb 25, 2014 by mosymeow_1

1 answer

How much heat is liberated when 100 mL of 1 N NaOH is neutralised by 300 mL of 1 N HCl ?

asked Feb 25, 2014 by mosymeow_1

1 answer

Find the sum of $20$ terms of the G.P., $0.15,0.015,0.0015................$

asked Feb 25, 2014 by rvidyagovindarajan_1

1 answer

Keeping in mind the enthalpy of formation of HF and HCl i.e. -161 kJ and -92 kJ, respectively, which of the following statements do you think is incorrect?

asked Feb 25, 2014 by mosymeow_1

1 answer

The molar heat capacity of water at constant pressure, $C_P$ is $75JK^{-1}mol^{-1}$. When 1.0 kJ of heat is supplied to 100 g of water which is free to expand, the increase in temperature of water is

asked Feb 25, 2014 by mosymeow_1

1 answer

For what value of $x$ the numbers $-\large\frac{2}{7},$$x,-\large\frac{7}{2}$ are in G.P.?

asked Feb 25, 2014 by rvidyagovindarajan_1

1 answer

Which term of the sequence $\large\frac{1}{3},\frac{1}{9},\frac{1}{27}.......$ is $\large\frac{1}{19683}$?

asked Feb 25, 2014 by rvidyagovindarajan_1

1 answer

Heat of combustion $\Delta H$ for $C(s), H_2(g)$ and $CH_4(g)$ are -94, -68 and -213 kcal/mol. Then $\Delta H$ for $C(s) + H_2(g) \rightarrow CH_4(g)$ is

asked Feb 25, 2014 by mosymeow_1

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An organic compound A upon reacting with $NH_3$ gives B. On heating B gives C. C in presence of $KOH$ reacts with $Br_2$ to give $CH_3CH_2NH_2$ A is :

asked Feb 25, 2014 by meena.p

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Which of the following condition depicts a favourable condition for a spontaneous reaction?

asked Feb 25, 2014 by mosymeow_1

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Compound $(A),C_8H_9Br$ gives a white precipitate when warmed with alcoholic $AgNO_3$. Oxidation of $(A)$ gives a acid $(B)$. $C_8H_6O_4.(B)$ easily forms anhydride on heating . Identify the compound $(A)$.

asked Feb 25, 2014 by meena.p

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Assume the enthalpy of combustion of methane and $CH_3OH$ are $x$ and $y$ respectively. If the enthalpy of $CH_4 + \frac{1}{2}O_2 \rightarrow CH_3OH$ is negative, then which relation is correct?

asked Feb 25, 2014 by mosymeow_1

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Given three reaction below, $N_2(g) + 3H_2(g) \leftrightharpoons 2NH_3(g); \Delta H_1$, $H_1(g) + Cl_2(g) \leftrightharpoons 2HCl(g) ; \Delta H_2$, $NH_3 (g) + 3Cl_2 \leftrightharpoons NCl_3(g) + 3HCl(g); -\Delta H_3$. In the terms of $\Delta H_1, \Delta H_2$ and $\Delta H_3$, heat of formation of $NCl_3(g)$ is

asked Feb 25, 2014 by mosymeow_1

1 answer

Which term of the sequence $\sqrt 3,3,3\sqrt 3.......$ is $729?$

asked Feb 25, 2014 by rvidyagovindarajan_1

1 answer

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