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Recent questions tagged chemistry
Questions
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 .
cbse
class12
chemistry
sec-c
ch-14
biomolecules
asked
Nov 10, 2016
by
meena.p
1
answer
Distinguish between rate expression and rate constant of a reaction
cbse
class12
chemistry
sec-c
ch-4
chemical-kinetics
asked
Nov 10, 2016
by
meena.p
1
answer
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 = $1.86 \;K \;mol^{-1}$)
cbse
class12
chemistry
sec-c
ch-2
solutions
asked
Nov 10, 2016
by
meena.p
1
answer
Give the preparation and uses of PVC
cbse
class12
chemistry
sec-b
ch-15
polymers
asked
Nov 10, 2016
by
meena.p
1
answer
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?
cbse
class12
chemistry
sec-c
ch-12
aldehydes-ketones-and-carboxylic-acids
asked
Nov 10, 2016
by
meena.p
1
answer
Account for the following: i)Fluorine does no show variable oxidation states while other members of the halogen family exhibit variable oxidation states. ii)Iodine is more soluble in $KI$ solution than in water. iii)Why do boiling points of noble gases increases down the group? iv)Why ammonia is a good complexing agent? v)Nitric oxide(NO) is a colourless gas becomes brown when released in air.
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 10, 2016
by
meena.p
1
answer
a)i)The resistance of a conductivity cell containing $0.001\;M\; KCl$ solution at $298\;K$ is $1500 \Omega$. What is the cell constant, if the conductivity of $0.001\;M\; KCl$ solution at $298\;K$ is $0.146 \times 10^{-3}\;S\;cm^{-1}$? ii)Explain with one example each the terms weak and strong electolytes iii)The standard reduction potential values of three metallic cations $X,Y, Z$ are $+0.52, − 3.03, − 1.18 V$ respectively. What will be the order of reducing power of the corresponding metals? b) Distinguish between rate expression and rate constant of a reaction
cbse
class12
chemistry
sec-e
ch-11
chemical-kinetics
asked
Nov 10, 2016
by
meena.p
1
answer
(a) Bring out the following conversions:. (i) 4-nitrotoluene to 2-bromobenzoic acid. (ii) Ethylcyanide to 1- phenyl propanone. (b) Give a reason for the following : (i) Chloroacetic acid is more acidic than acetic acid. (ii) Carboxylic acids have higher boiling point than alcohols. (iii) 4-nitrobenzoic acid is more acidic than 4-methoxy benzoic acid.
cbse
class12
chemistry
sec-e
ch-12
aldehydes-ketones-and-carboxylic-acids
asked
Nov 10, 2016
by
meena.p
1
answer
(a) Compare non transition and transition elements on the basis of their (i) Variability of oxidation states (ii) stability of oxidation states. (b) Give chemical reactions for the following observations: (i) Potassium permanganate is a good oxidising agent in basic medium. (ii) Inter convertibility of chromate ion and dichromate ion in aqueous solution depends Upon pH of the solution. (iii) Potassium permanganate is thermally unstable at $513\;K$.
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 10, 2016
by
meena.p
1
answer
(I)(a) Calculate the boiling point of a solution containing $0.61\;g$ of benzoic acid in $5\; g$ of $CS_2$ .Assuming $84\%$ dimerisation of acid. The boiling point and $K_b$ of $CS_2$ are $46.2^{\circ}0C$ and $2.3\; K\; Kg \;mol^{-1}$ respectively. (b) State Raoult's law for the solution containing non-volatile solute. Give its mathematical expression also. (II) 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 ?
cbse
class12
chemistry
sec-e
ch-4
chemical-kinetics
asked
Nov 10, 2016
by
meena.p
1
answer
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 . $HClO_4 < HClO_3 < HClO_2 < HClO$
cbse
class12
chemistry
sec-c
ch-12
aldehydes-ketones-and-carboxylic-acids
asked
Nov 9, 2016
by
meena.p
1
answer
Out of C and CO, Which is better reducing agent at $673\;k$
cbse
class12
chemistry
sec-b
ch-3
electrochemistry
asked
Nov 9, 2016
by
meena.p
1
answer
Why is an increase in temperature observed on mixing chloroform with acetone ?
cbse
class12
chemistry
sec-b
ch-1
solid-state
asked
Nov 9, 2016
by
meena.p
1
answer
Ionic solid conduct in the molten state but not in the solid state . Explain
cbse
class12
chemistry
sec-b
ch-1
states-of-matter-solid-state
asked
Nov 9, 2016
by
meena.p
1
answer
(a) Write a suitable chemical equation to complete each of the following transformations: (i) Butan-1-ol to butanoic acid . ( ii) 4 -Methylacetophenone to benzene -1,4-dicarboxylic acid (b) Suggest a reagent for conservation of ethanol to ethanoic acid
cbse
class12
chemistry
sec-e
ch-11
alcohols-phenols-and-ethers
asked
Nov 9, 2016
by
meena.p
1
answer
(a)Define the following terms : (i) Mole fraction (ii) Ideal solution (b) 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 ?
cbse
class12
chemistry
sec-e
ch-4
chemical-kinetics
asked
Nov 9, 2016
by
meena.p
1
answer
(a)Draw the molecular structure of the following compounds : $(i)N_2O_5 (ii) X_eOF_4$ (b) Why do the d-block elements exhibits a large number of oxidation states than f - block elements
cbse
class12
chemistry
sec-e
ch-8
d-and-f-block-elements
asked
Nov 8, 2016
by
meena.p
1
answer
Pickles have a long self - life and do not get spoiled for month . why ?
cbse
class12
chemistry
sec-a
ch-16
chemistry-in-everyday-life
asked
Nov 8, 2016
by
meena.p
1
answer
a)What are polysaccharides ? Give one example b)Give the preparation and uses of PVC
cbse
class12
chemistry
sec-c
ch-15
polymers
asked
Nov 8, 2016
by
meena.p
1
answer
Name the alkyl halide and sodium alkaloid used to synthesize tert - butyl ether
cbse
class12
chemistry
sec-a
ch-11
alcohols-phenols-and-ethers
asked
Nov 8, 2016
by
meena.p
1
answer
Arrange following complex ions in increasing order of crystal field splitting energy $(\Delta _0)$: $[Cr(Cl)_6]^{3-},[Cr(CN)_6]^3,[Cr(NH_3)_6]^{3+}$
cbse
class12
chemistry
sec-a
ch-9
coordinate-compounds
asked
Nov 8, 2016
by
meena.p
1
answer
What causes Brownian movement in a colloidal solution ?
cbse
class12
chemistry
sec-b
ch-2
solutions
asked
Nov 8, 2016
by
meena.p
1
answer
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
cbse
class12
chemistry
sec-c
ch-14
biomolecules
asked
Nov 8, 2016
by
meena.p
1
answer
How do you explain the presence of an aldehydic group in a glucose molecule ?
cbse
class12
chemistry
sec-c
ch-13
amines
asked
Nov 7, 2016
by
meena.p
1
answer
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 ?
cbse
class12
chemistry
sec-c
ch-11
alcohols-phenols-and-ethers
asked
Nov 7, 2016
by
meena.p
1
answer
p- Dichlorobenzene has higher melting point and lower solubility than o- and m- isomers Discuss.
cbse
class12
chemistry
sec-c
ch-7
p-block-elements
asked
Nov 7, 2016
by
meena.p
1
answer
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 ?
cbse
class12
chemistry
sec-c
ch-4
chemical-kinetics
asked
Nov 7, 2016
by
meena.p
1
answer
Why are pentahalides more covalent than trihalides ?
cbse
class12
chemistry
sec-c
ch-10
haloalkanes-and-haloarenes
asked
Nov 7, 2016
by
meena.p
1
answer
Why is it advantageous to roast a sulphide ore to the oxide before reduction ?
cbse
class12
chemistry
sec-c
ch-6
isolation-of-elements
asked
Nov 7, 2016
by
meena.p
1
answer
How do size of particles of absorbent , pressure of gas and prevailing temperature enfluence the extent of absorption of a gas on a solid ?
cbse
class12
chemistry
sec-c
ch-9
coordinate-compounds
asked
Nov 7, 2016
by
meena.p
1
answer
Differenciate between rate of reaction and reaction rate constant
cbse
class12
chemistry
sec-c
ch-6
isolation-of-elements
asked
Nov 4, 2016
by
meena.p
1
answer
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.
cbse
class12
chemistry
sec-c
ch-5
surface-chemistry
asked
Nov 4, 2016
by
meena.p
1
answer
Why is boiling point of water increased on addition of sodium chloride into it ?
cbse
class12
chemistry
sec-c
ch-3
electrochemistry
asked
Nov 4, 2016
by
meena.p
1
answer
Explain why does conductivity of germanium crystals increase on doping with gallium
cbse
class12
chemistry
sec-c
ch-2
solutions
asked
Nov 4, 2016
by
meena.p
1
answer
How do you explain the functionality of monomer?
cbse
class12
chemistry
sec-b
ch-15
polymers
asked
Nov 4, 2016
by
meena.p
1
answer
Explain giving a reason for each of the following situation : (i) In aqueous medium, HCl is stronger acid than HF (ii) White phosphorus is more reactive than red phosphorous.
cbse
class12
chemistry
sec-b
ch-7
p-block-elements
asked
Nov 4, 2016
by
meena.p
1
answer
Calculate the equilibrium constant $K_c$ for the reaction . $3Sn^{4+} +2Cr \to 3Sn^{2+}+2Cr^{3+}$Given $E^0 =0.885\;V$
cbse
class12
chemistry
sec-b
ch-3
electrochemistry
asked
Nov 4, 2016
by
meena.p
1
answer
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 .
cbse
class12
chemistry
sec-c
ch-2
solutions
asked
Nov 4, 2016
by
meena.p
1
answer
Copper crystallizer into an fcc lattice with edge length $3.61 \times 10^{-8}\;cm$ Show that the calculated density is in agreement with its measured value of $8.92 \;g\;cm^{-3}$
cbse
class12
chemistry
sec-b
ch-1
states-of-matter-solid-state
asked
Nov 4, 2016
by
meena.p
1
answer
Where are receptors located ?
cbse
class12
chemistry
sec-a
ch-14
biomolecules
asked
Nov 4, 2016
by
meena.p
1
answer
Write the structure of 4 - methyl pent -3-en -2- one
cbse
class12
chemistry
sec-a
ch-12
aldehydes-ketones-and-carboxylic-acids
asked
Nov 4, 2016
by
meena.p
1
answer
How do you account for the miscibility of ethoxyethane with water.
cbse
class12
chemistry
sec-a
ch-11
alcohols-phenols-and-ethers
asked
Nov 4, 2016
by
meena.p
1
answer
Which compound is used to estimate the hardness of water volumetrically?
cbse
class12
chemistry
sec-a
ch-9
coordinate-compounds
asked
Nov 4, 2016
by
meena.p
2
answers
Why is ferric chloride preffered over potassium in case of a cut leading to bleeding ?
cbse
class12
chemistry
sec-a
ch-5
surface-chemistry
asked
Nov 4, 2016
by
meena.p
1
answer
Low density polythene and high density polythene , both are polymers of ethene but there is marked difference in their properties . Explain
cbse
class12
chemistry
sec-c
ch-15
polymers
asked
Nov 4, 2016
by
meena.p
1
answer
How do antiseptics differ from disinfectant? Give one example of each case
cbse
class12
chemistry
sec-c
ch-14
biomolecules
asked
Nov 4, 2016
by
meena.p
1
answer
Differentiate between chiral and achiral molecules :
cbse
class12
chemistry
sec-c
ch-10
haloalkanes-and-haloarenes
asked
Nov 3, 2016
by
meena.p
1
answer
$CuSO_4.5H_2O$ is blue in colour while $CuSO_4$ is colourless . why ?
cbse
class12
chemistry
sec-c
ch-9
coordinate-compounds
asked
Nov 3, 2016
by
meena.p
1
answer
Why do the d-block elements exhibits a large number of oxidation states than f - block elements
cbse
class12
chemistry
sec-c
ch-8
d-and-f-block-elements
asked
Nov 3, 2016
by
meena.p
1
answer
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.
cbse
class12
chemistry
sec-c
ch-7
p-block-elements
asked
Nov 3, 2016
by
meena.p
1
answer
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