HALF YEARLY EXAMINATION : 2020–21

Class : XI (ISC)
Time : 3 hrs. Chemistry Paper -1 (Theory) M.M.: 70
Instructions :
Candidates are allowed additional 15 minutes for only reading the paper. They must NOT
start writing during this time.
All questions are compulsory.
Question 1 is of 20 marks having four subparts, all of which are compulsory.
Question 2 to 8 carry 2 marks each with two questions having Internal choice.
Question 9 to 15 carry 3 marks each, with any two questions having Internal choice.
Questions 16 to 18 carry 5 marks each, with an internal choice.
The intended marks for questions or parts of questions are given in [ ] .
Balanced equations must be given wherever possible and diagrams where they are helpful.
When solving numericals all essential working must be shown.
In working out problems, use the following data, R = 1.987 Cal deg–1 mol–1 = 8.314 JK–1 mol–1
=0.0821 L atm K–1 mol–1 Avogadro's No- 6.023×1023

PART – I [20 Marks]

Q.1. a) Fill in the blanks by choosing the appropriate word from those given in the
brackets : [4]
[ Aliphatic , +5, +4, o, -1, reducing , oxidising, aromatic, alicyclic, heterocyclic, 3, 4, 5,
poor donor, good donor, good acceptor, Poor acceptor ]
i) In BrO 3 the oxidation state of Br is and in Br2 is .
ii) Alkali metalsare strong agent because they are of electron.
iii) Cyclopropane is while benzene is
iv) Fe has unpaired electron but Fe3+ has unpaired electron.
b) Complete the following statement by selecting correct alternative : [4]
O O
|| ||
i) Correct IUPAC name for CH3–C–CH2–CH2–C–OH is :
a) 1-hydroxy -pentane-1, 4-dione
b) 1, 4 dioxobutanol
c) 1-carboxy-butane-3-one
d) 4-oxopentanoic acid
ii) In CH3 CH=CH2 number of s bond and p bond respectively is :
a) 8, 1 b) 9, 1 c) 8, 2 d) 7, 1
iii) Number of electron spinning clockwise in third shell is :
a) 4 b) 9 c) 7 d) 6
iv) The order of electron gain enthalpy (DegH) for halogen is :
a) F>Cl>Br>I b) I>Br>Cl>F c) I>Cl>Br>F d) Cl>F>Br>I
c) Match the following: [4]
a) n=3 l=o i) Positively charged
b) Carbonium ion ii) Heterocyclic compound
c) Carbanion iii) Two electron
d) Pyridine iv) lone pair of electron
d) Answer the following : [8]
i) a) State (n+l) rule
b) Write electronic conguration of Cu(z=29)
ii) First ionisation enthapy of N is greater than O why?
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 iii) How much water is to be added in 100 ml of 2N HCl to make it N 5 HCl.
iv) a) Sodium is less reactive than potassium why.
b) Anion is always bigger than its parent atom why?
Q.2. a) At 25ºC and 760 mm of Hg pressure a gas occupies 600 ml volume what will be
its pressure at a height where temperature is 10ºC and volume of gas is 640 ml. [2]
OR
b) What mass of CaCO3 is required to react completely with 100 ml of 0.75 N HCl .
Q.3. Balance the following equation by ion electron method in acidic medium [2]
-- -- + +++
Cr2 O 7 + C 2 O 4 + H ¾ ¾® Cr + CO 2 + H 2 O
Q.4. Write electronic conguration of following : [2]
Mn++ (z=25) Zn++ (z=30)
Q.5. A sugar solution of 214.2 gm contains 34.2 gm sugar (C12 H22 O11) calculate : [2]
i) molality of solution ii) mole fraction of sugar
Q.6. Dene the following : [2]
i) Hund's Rule ii) Ionisation Enthalpy
Q.7. i) Write two uses of plaster of paris.
ii) How plaster of paris is prepared from Gypsum write chemical equation. [2]
OR
Write principle ienvolved in solvay ammonia method for manufacturing of
sodium carbonate. (Give Equations)
Q.8. Write IUPAC name of following compound : [2]
i) CH3–CH–C–CH–COOH ii) COOH
| || |
OH O CH3 NO2
Q.9. a) Find out the period number and group number of following element in long form
of periodic table : [3]
i) X(z=36) ii) Y(z=23) iii) Z(z=20)
OR
b) 0.25 gm of a dibasic acid is dissolved in water to make 100 ml solution. 10 ml of
this solution is completely neutralised with 12.5 ml of N 30 NaOH. Find equivalent
mass of acid.
Q.10. i) The rst ionization enthalpy DH1 and second ionization enthalpy DH2 and electron
gain enthalpy (Deg.H) of few element are given.
Element DH1 (KJ/mol) DH2 (KJ/mol) (Deg.H) (KJ/mol)
A 520 7300 60
B 738 1451 -40
C 1681 3374 –328
D 2372 5251 +48
Answer the following ; which element is :
1) Least reactive element.
2) An Alkali metal
3) Most reactive non metal.
4) Metal which form halide of the type Mx2 .
ii) Arrange the following isoelectronic ion in the increasing order of Radii [3]
+ 3– – –– ++ 3+
Na , N , F , O , Mg , Al
Q.11. Write balanced equation for following conversion : [3]
1) Ethanoic acid to methane 2) Methane to methyl chloride
3) Methyl chlride to Ethane
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Q.12. A sample of 0.5 gm ofan organic compound was treated according to Kjeldahl's method
the ammonia evolved was absorbed in 50 ml 1N H2SO4 . The residual acid required

60 ml N 2 NaOH for neutralisation. Calculate percentage of N in compound. [3]

Q.13. a) Mention type of reagent and type of reaction in the following : [3]
1) CH3–Cl+OH– CH3OH+Cl–
+ Cl
2) +Cl +H
+

3) CH2=CH2+H–Br CH3–CH2–Br
OR
b) Find the type of isomerism in the following cmpounds :
1) CH3 CH2 OH and CH3 – O–CH3
2) CH3–CH2–CH2–OH and CH3– CH–CH3
|
OH
3) CH3–CH2–CH2–CH3 and CH3–CH–CH3
|
CH3
Q.14. a) Find oxidation state of underlined element : [3]
---
i) PO 4 ii) O3 iii) Ni(CO)4 iv) H2SO5
b) Balance following equation by oxidation number method :
Cr2 O 7- - + SO 2 + H + ¾
¾® Cr + + + + SO -4 - + H 2 O
Q.15. Arrange the following as directed : [3]
CH3
|
⊕ ⊕ ⊕
i) CH 3 C H 2 , CH3–C ⊕ , C H 3 , CH 3 C H CH 3
|
CH3
Increasing order of stability.
ii) LiOH , KOH , NaOH , RbOH , C5OH
Increasing order of Alkaline character.
iii) BeCO3 , MgCO3 , CaCO3 , Sr CO3 , BaCO3
decreasing order of solubility
N
Q.16. i) 1.725 gm metal carbonate react with 300 ml HCl. Excess of HCl require
10
N
10 ml NaOH for complete neutralisation . Calculate equivalent weight of
2
metal carbonate. [5]
ii) Mole fraction of ethanol in a mixture of ethanol and water is 0.04. Calculate
molality of solution.
OR
i) Calculate the temperature at which 28 gm of nitrogen gas occupy a volume of
10 litre at 2.46 atm pressure ?
ii) 250 ml of N2 at 720 mm Hg pressure and 380 ml of O2 at 650 mm Hg pressure
are put together in one litre ask. If the temperature kept constant. What will
be the nal pressure of the mixture.

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Q.17. i) Complete and balance the following reaction : [5]
1) Na2 S2 O3 + I2
2) Na2 S2 O3 + HCl
3) CaO + SiO2
ii) Give reason :
1) LiCl is covalent but NaCl is ionic in nature why?
2) Cs is used in photoelectric cells why?
OR
i) Find out oxidising and reducing agent in the following reaction :
1) MnO2 + 4HCl MnCl2 + 2H2O + Cl2
2) SnCl2 + 2FeCl3 SnCl4 + 2FeCl2
ii) Balance the equation by ion electron method :
MnO -4 +Fe++ + H+ Mn++ + Fe+++ + H2O
Q.18. i) Write IUPAC name of the following : [5]
O OH
OH
1) 2) OH
O CH 3
OH
3)
CH3
ii) Draw structure of following compound :
1) 4-Hydroxy-2-methyl pentanal
2) Pentane-2, 4-dione
OR
i) Complete the following Equation :
Zn-Hg
1) CH3CHO +[H]
conc.HCl
2) CH3CH2OH +HI Red P
hv
3) CH3 CH3+Cl2 x
(diffused sunlight+
ii) a) Write cis and trans isomer of but-2-ene
b) Write d and l form of lactic acid

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