1.
[1]
Identify the equivalent weight of K2Cr2O7 in the following reaction?
Chemistry
NEB — CLASS 12
Chemistry
Model Question
Answer each question in your own words as far as practicable. The figures in the margin indicate full marks.
सबै प्रश्नको उत्तर दिनुहोस् । (Attempt All Questions)
Time : 3 hrsPass Marks : 27Full Marks : 75
2.
[1]
In a solution that is at equilibrium, what happens to the
concentration of H+ ions if the concentration of OH- ions
is increased?
3.
[1]
Assuming the rate of a reaction is doubled for every 10°C rise
in temperature, how many times does the rate increase if
temperature rises from 10°C to 100°C?
4.
[1]
For the given reactions:
i. C + O2 → CO2, ΔH = -x KJmol-1
ii. 2CO + O2 → 2CO2, ΔH = -y KJmol-1
The enthalpy of formation of CO becomes
5.
[1]
What product would be obtained if red hot copper wire reacts with
steam?
6.
[1]
For which manufacturing process, Bessemer converter is used?
7.
[1]
When sodium phenoxide reacts with methyl bromide it gives
8.
![]()
[1]
Identify the X in the following reaction:
9.
[1]
Which of the following reagents can be used to distinguish between
a phenol and a carboxylic acid?
10.
[1]
The colorless sweet smelling liquid compound A
which exposed in air forms poisonous phosgene and also reacts with
acetone gives sleep-inducing drug. Predict the product when the
compound A reduced in a neutral medium?
11.
[1]
Oxygen containing organic compounds upon oxidation forms a
carboxylic acid as the major organic product with its molecular
mass higher by 14 units. Identify the organic
compound.
12.
[1]
a) A solution of HCl is labelled 2M. Clarify its meaning?
The addition of solution of required concentration in a reaction mixture yields profitable products and saves reactants.
b) In which aspects molarity is different from molality?
c) List the significance of normality factor in preparation of standard solution?
d) Liquor ammonia kept at a corner of your chemistry lab is 25% (w/w) NH3 and its specific gravity is 0.91. Find the molarity of liquor ammonia.
13.
[1]
13. a) Write down the differences between rate of reaction and rate constant. (2)
b) For the reaction 2A+B→product, following data were obtained
| Experiment | [A], moleLitre-1 | [B], moleLitre-1 | Initial rate, moleLitre-1 S-1 |
|---|---|---|---|
| 1 | 0.50 | 0.50 | 1.6×10-4 |
| 2 | 0.50 | 1.00 | 3.2×10-4 |
| 3 | 1.00 | 1.00 | 3.2×10-4 |
Find,
i) order with respect to A and B. (1)
ii) the value of the rate constant of the reaction (1)
iii) the rate of reaction when the concentration of A and B is 0.5M and 0.4 M, respectively. (1)
Or,
Four metals A, B, C and D react in the following way:
B displaces only A from solution. Only D and C displaces hydrogen from 1M HCl solution. None of the metals will displace C from solution. Answer the followings:
i) Make the activity series of four metals with hydrogen
ii) The standard potential for the following electrodes are:
C++ + 2e- → C, E° = 0.76V
D+++ + e- → D++, E° = +0.77V
a) Construct the galvanic cell by pointing out cathode and anode.
b) With 1M solution of the ions, what will be EMF of cell?
c) Will the reaction occur: C++ + 2D++ → C + D+++. Occur? Give reasons.
14.
[3]
An ammonia solution is added to the sulphate of coinage metal A, the blue precipitates (B) which appears dissolves in excess of reagent to form deep blue solution (C). Answer the followings:
a) Identify A, B and C with sequence of chemical reaction.
b) Predict the electronic configuration of this metal A.
c) Select the suitable methods for the purification of metal A?
15.
[1]
What is meant by d-d electron transitions? List the characteristics
of transition metals.
16.
[1]
Write down the structural formula and IUPAC name of tertiary
alcohol with formula C4H10O. How would you apply Victor Meyer’s
method for the distinction of 1-propanol and 2-propanol? Explain.
17.
[3]
An organic compound X reacts with methyl magnesium bromide followed by acidic hydrolysis yields the compound Y. The compound Y on oxidation with acidified KMnO4 yields Z. All three gives positive iodoform test. Answer the followings:
a). Predict the compounds X, Y and Z with sequence of reaction and give their IUPAC names.
b) Make the product by reacting Z with dilute NaOH?
OR
An organic compound(X) when heated with acetone gives hypnotic and nervous sedatives drugs and form carbonyl chloride when it exposes to air
a) Predict the organic compound (X)
b) Write the reactions for the formation of (X) from ethanol.
c) Predict compound the new compound by treating (X) with conc. nitric acid?
d) Convert (X) into acetylene.
18.
[1]
Nitro group in nitrobenzene is meta-directing group towards electrophilic substitution reaction, why? How does nitrobenzene react with?
i) Zn/NH4Cl ii) LiAlH4
b) What are the isomers of formula C2H7N?
19.
[5]
(a) Reimer–Tiemann’s reaction
(b) Perkin’s condensation reaction
(c) Williamson’s ether synthesis
(d) Cannizzaro’s reaction
(e) Sandmeyer’s reaction
20.
[3]
The expressions of Ostwald's dilution law is,
α = Kₐ/C
a) Derive it.
b) What information can you obtain from this expression?
c) Will strong electrolytes obey this expression, why?
d) 0.1M ethanoic acid is 1.34% ionized. Find its dissociation constant.
Or,
a) Hess' law is applied to calculate different types of enthalpy of reaction.
i) Illustrate the Hass law of constant heat summation.
ii) Standard enthalpy of combustion of C (g); H2 (g) and C2H2 (g) are -394 KJ mol-1, -286 KJ mol-1 and -1300 KJ mol-1 respectively. Calculate enthalpy of formation of acetylene.
b) Draw the energy profile diagram of exothermic and endothermic reaction.
21.
[1]
An organic compound C2H4O2 has two functional isomers A and B. Isomer A changes blue litmus into red and B has fruity smell.
a) Give the reaction for the formation of A by using Grignard's reagent.
b) Convert the isomer A into isomer B?
c) Write a suitable test reaction to distinguish A from methanoic acid.
d) Arrange the following in the decreasing order of their acidic strength and give reason for your answer.
CH3COOH, ClCH2COOH, FCH2COOH, C6H5COOH
e) Identify A and B of the following reactions.
OR,
Amines are formally derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group which may respectively be called alkyl amines and aryl amines.
a) Give a test to distinguish alkyl amine and aryl amine.
b) How can you separate ethylamine and dimethylamine present in mixture by Hoffmann's method?
c) Arrange the following amines in terms of increasing order of basic strength.
Propyl amine, ethyl methylamine, trimethylamine.
d) Convert: ethanamine to methanamine
22.
[2]
a. How are cement classified on the basis of hardening and setting behavior?
b. Differentiate between
i. paper and pulp
ii. artificial and natural radio activity
iii. addition and condensation polymer
b. Differentiate between
i. paper and pulp
ii. artificial and natural radio activity
iii. addition and condensation polymer