|
|
Do you want 100% Marks with less
effort Prepare the Following YSA Paper for YOU.?
Class – XII
Subject – Chemistry
Time: 3 Hours M.M.70
General Instructions:
1. All questions are compulsory.
2. Question nos. 1 to 8 are very short
answer questions and carry 1 mark each.
3. Question nos. 9 to 18 are short
answer questions and carry 2 marks each.
4. Question nos. 19 to 27 are also short
answer questions and carry 3 marks each
5. Question nos. 28 to 30 are long
answer questions and carry 5 marks each
6. Use log tables if necessary, use of
calculators is not allowed.
1. What is the efficiency of packing in
case of a metal crystal for body-centred cubic
2. What are micelles?
3.State the role of silica in the
metallurgy of copper.
4.Draw structures of XeF2 and PCl5(g).
5.Give IUPAC name of (CH3CH2)2NCH3
6.Give a chemical test to distinguish
between Secondary and tertiary amines
7.Name the vitamin responsible for
Pernicious anaemia.
8.Give the structure and name of
monomers of Buna-N.
9. State Henry’s law and mention some important
applications?
10.Predict the products of electrolysis
in each of the following:
(i) An aqueous solution of AgNO3 with
silver electrodes.
(ii) An aqueous solution of AgNO3 with
platinum electrodes.
11. The conversion of molecules X to Y
follows second order kinetics. If concentration of X is
increased to three times how will it affect the rate of
formation of Y ?
12 Describe a method for refining
nickel.
13. (a) Give the reason for bleaching
action of Cl2.
(b) Name two poisonous gases which can
be prepared from chlorine gas.
14. Describe the following : (a)Finkelstein
reaction (b) Swarts reaction.
15. Compare acidity of phenol with that
of ethanol.
16. In the following pairs of halogen
compounds, which would undergo SN2 reaction faster?
17. Haloalkanes react with KCN to form
alkyl cyanides as main product while AgCN forms isocyanides
as the chief product. Explain.
18.How are following prepared? Give one
use of each. (i) PVC(ii)Dacron .
19.(a) Suggest the most important type
of intermolecular attractive interaction in
the following pairs. (i) n-hexane and
n-octane (ii) NaClO4 and water
b) If the density of some lake water is
1.25g mL–1 and contains 92 g of Na+ ions per
kg of water, calculate the molality of
Na+ ions in the lake.(Atomic mass=23)
20. In the button cell widely used in
watches and devices the following reaction takes place: Zn
(s)+ Ag2O(s) + H2O(l)à Zn2+(aq) + 2 Ag(s) + 2OH- (aq)
Determine ΔrG0 &E0 for the reaction. EoZn2+/Zn =
-0.76V, EoAg+/Ag = + 0.80V
21.(a) An element has a body-centred
cubic (bcc) structure with a cell edge of
288 pm. The density of the element is
7.2 g/cm3. How many atoms are present in 208 g of the
element?
(b) A group 14 element is to be
converted into n-type semiconductor by doping it with a
suitable impurity. To which group should this impurity
belong?
22 The rate of a reaction quadruples
when the temperature changes from 293 K to 313 K. Calculate
the energy of activation of the reaction assuming that it
does not change with temperature.
23.(a) What are emulsions? What are
their different types? Give example of each type.
(b) Explain what is observed when a beam
of light is passed through a colloidal sol.
24(a) [Cr(NH3)6]3+ is paramagnetic while
[Ni(CN)4]2– is diamagnetic. Explain why?
(b) Give evidence that [Co(NH3)5Cl]SO4
and [Co(NH3)5SO4]Cl are ionization isomers.
25.(i) Why cannot aromatic primary
amines be prepared by Gabriel phthalimide synthesis?
(ii) Although amino group is o– and
p– directing in aromatic electrophilic substitution
reactions, aniline on nitration gives a substantial amount
of m-nitroaniline.Explain
(iii) Aniline does not undergo Friedel-Crafts
reaction. Explain
26.(a) What are essential and
non-essential amino acids? Give two examples of each type.
(b) What type of bonding helps in stabilising the α-helix
structure of proteins?.
27.Explain giving examples: (a)Antihistamines
(b)Antifertility drugs (c)Analgesics
OR
(a) . What problem arises in using
alitame as artificial sweetener ?
(b) Why are cimetidine and ranitidine
better antacids than sodium hydrogencarbonate or magnesium
or aluminium hydroxide ?
28(a).How is SO2 an air pollutant?
(b)Why are halogens strong oxidising
agents?
(c) Explain why fluorine forms only one
oxoacid,
HOF
.
(d)Explain why inspite of nearly the
same electronegativity, oxygen forms
hydrogen bonding while chlorine does
not.
(e) Why are halogens coloured?
Or
28. (a)Why does R3P = O exist but R3N =
O does not (R = alkyl group)?
(b)Explain why NH3 is basic while BiH3
is only feebly basic.
(c)Nitrogen exists as diatomic molecule
and phosphorus as P4. Why?
(d)Why does nitrogen show catenation
properties less than phosphorus?
(e)Give the disproportionation reaction
of H3PO3.
29.(a) Describe the preparation of
potassium permanganate. How does the acidified permanganate
solution react with (i) iron(II) ions (ii) SO2 and (iii)
oxalic acid?
Write the ionic equations for the
reactions.
Or
29.(a) Name the oxometal anions of the
first series of the transition metals in which the metal
exhibits the oxidation state equal to its group number.
(b) What are the different oxidation
states exhibited by the lanthanoids?
(c) suggest reasons for the following
features of the transition metal chemistry:
(i) The lowest oxide of transition metal
is basic, the highest is amphoteric/acidic.
(ii) A transition metal exhibits highest
oxidation state in oxides and fluorides.
30.(a)Arrange the following compounds in
increasing order of their reactivity in
nucleophilic addition reactions. :Ethanal,
Propanal, Propanone, Butanone.
(b) Which acid of each pair shown here
would you expect to be stronger? CH3CO2H or CH2FCO2H
(c) Although phenoxide ion has more
number of resonating structures than carboxylate ion,
carboxylic acid is a stronger acid than phenol. Why?
(d) What is Rosenmund reaction ?
Or
a. An organic compound ‘A’ with
molecular formula C5H8O2 is reduced to n-pentane on
treatment with Zn-Hg/HCI. ‘A’ forms a dioxime with
hydroxylamine and gives a positive iodoform test and
Tollen’s test. Identify the compound A and deduce its
structure
b. An aromatic compound A on treatment
with aqueous ammonia and heating forms compound B which on
heating with Br2 and KOH forms a compound C of molecular
formula C6H7N .Write the structures and IUPAC names of
compounds A,B,C.
|
|
|
