Chemistry
Previous year question paper with solutions for Chemistry Mar-2018
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Question paper 1
1. Out of 1M urea solution and 1M Kc/ solution, which one has higher freezing point ?
Answer:
1M urea has a higher freezing point.
2. what are the units of Rate constant for First order reaction ?
Answer:
Rate = K[A]1
= Kmol-1R =
=> S-13. What' is Tollen's reagent ?
Answer:
Tollen’s reagent is a chemical reagent used to determine the presence of aldehyde, aromatic aldehyde and hydroxyl ketone functional group.
4. How is benzamide converted into benzylamine ?
Answer:
C2H5CONH2 + Br2 + 4KOH →
C6H5NH2 + K2CO3 + 2KBr + 2H2O5. Predict the products in the following reaction :
Answer:
6. The chemical name of Vitamin E ...................
Answer:
Alpha – Tocophenol; D – alpha Tocophenol.
7. The class of drugs used for the treatment of cut or wound is :
(a) Tranquillizers (c) Antihistamins
(b) Antiseptics (d) AntiPyretic
Answer:
Antiseptics.
8. Soft soaps are potassium salts of higher fatty acids.True/False
Answer:
True
9. In a metallic oxide, oxide ions are arranged in cubic close packing. One sixth of the tetrahedral voids are occupied by cations p and one third of octahedral voids are occupied by the cation Q. Deduce the formula of the compound.
Answer:
(one sixth of tetrahedral) P
Q
O1→ (octahedral voids).=> PQO3
10. For a reaction rate law expresslon is :
Rate = K [A]1/2 [B]2
Can the reaction be an elementary ? Explain.
Answer:
Number of an elementary process would have a rate law order equal to its molecularity and therefore must be integer values.
Rate = K[A]1/2 [B]2
Order =
Order = 2.5
The order can be a fractional value. Hence it’s not an elementary reaction.
11. Explain Mond's process used for refining of nickel?
Answer:
In this process, nickel is heated in the presence of carbon monoxide to form nickel tetra carbonyl which is a volatile complex.
Ni + 4CO
Ni(CO)4.Ni(CO)4
Ni + CO.The obtained nickel tetra carbonyl is decomposed by subjecting it to higher temperature to obtain nickel.
12. Why do transition metals have high enthalpies of atomization?
Answer:
Transition elements have high effective nuclear charge and number of valence electrons. Therefore, they form strong metallic bonds. As a result, the enthalpies of atomization of transition elements is high.
13. [Fe(CN)6]-3 is low spin complex but [Fe(H2O)6]+3 is high spin complex Explain
Answer:
In the presence of CN – the 3d electrons pair up leaving only one unpaired electron. The hybridisation is d2SP3 forming an inner orbital complex in the presence of H2O. 3d electrons do not pair up. The hybridisation is SP3d2 forming an outer orbital complex containing five unpaired electrons.
[Fe(CN)6]-3 has a low spin complex because it has the lowest number of unpaired electrons for an octahedral iron(iii) complex. [Fe(H2O)6]-3has a high spin because it has the number of electrons.
14. Why does acetylation of -NH2 group of aniline reduce its activity ?
Answer:
Acetylation of aniline reduces its activation effect because it results in decrease of electron density on nitrogen. Due resonance, the electron pair of nitrogen atom gets delocalised towards the carbonyl group.
15. what are Biodegradable polymers ? Give chemical equation for the preparation of any one biodegradable Polymer.
Answer:
Biodegradable polymers are polymers which are degraded by micro-organisms within a given period of time so that biodegradable polymers and the degraded product do not cause effects on the environment egDextron, Nylon2-nylon-6.
These polymers are mainly used for medical purposes such as surgical materials, tissue in growth materials for controlled drug release etc. They are also used in agriculture film seed coating, fast food wrappers etc. poly-B hydroxybutyrate-CO-B-hydroxyvalerate (PHBV) is a biodegradable aliphatic polyester.
16. Write two structural differences between DNA and RNA.
Answer:
DNA
RNA
The sugar moiety in DNA molecules is b-D-2 deoxyribose.
The sugar moiety in RNA molecules is b-Ribose.
DNA contains uracil.
RNA contains thymine.
Doesn’t contain thymine.
Doesn’t contain uracil.
The helical structure of DNA is a double strand.
The helical structure of RNA is a single strand.
17. (a) Analysis shows nickel oxide has the formula Ni0.98 O1.00 what fraction of Ni exists as Ni2+ and Ni3+ ions in given oxide ?
(b) Explain metal deficiency defect due to catron vacancies.
Answer:
(a) Formula of Ni0.98 O1.00
So, the ratio of Ni : O => 98: 100, hence there are 100 atoms of oxygen and 98 atoms of nickel.
Let number of atoms of Ni2+ = x
Let number of atoms of Ni3+ = 98-x
Charge of Ni = charge on O
Hence oxygen has a charge of -2
3(98-x) + 2x = 2(100)
294 – 3x + 2x = 200
+x = +94
x = 94
percentage of Ni2+ = (atoms of Ni+2/ total number of Ni) 100
=>
=> 96%
Percentage of Ni3+ = 100 – Ni+2
= 100 – 96
= 4%
18. (a) When HgI2, is added to aqueous solution of KI, why there is an increase in osmotic pressure of solution?
(b) Commercially available HCl contains 38% HCl by mass. calculate molality of the solution.
Answer:
(a) Freezing point of the solution with increase. Mercuric Iodide will react with potassium iodide to form dipotassium tetra iodo mercury. The reaction is given by:-
2KI + HgI2 = K2[HgI4]. This associate will decrease the number of ions in the solution as a result of Van’t Hoff factor will decrease as n decrease from 4 to 3.
Molarity = 12.61 Molar and 7.96ml of HCl (38%) needed for 1.0 litres of 0.10 Molar HCl.
(b) HCl(38%) =
=
=> moles of HCl in 38g =
=> volume of solution containing 1.06 mole of HCl =
Molarity of HCl (38%) =
= 12.62Molar HCl
19. (a) Explain Normal or Standard hydrogen electrode.
(b) How much amount of substance is deposited by passing one Faraday of electricity?
Answer:
(a) The standard hydrogen electrode is the standard measurement of electrode potential for the thermodynamic scale of redox potentials. The standard hydrogen electrode is called (SHE) or maybe known as normal hydrogen electrode (NHE)
2H+ + 2e-→ H2(g) at 250C
(b) Faraday is a unit of charge not electricity. Passing one faraday charge can yield one mole a substance having a single charge on each molecule or atom.
OR
19. Calculate the cell potential (Ecell) of the following cell at 298K.
Ag(s) l AgNO3 (0.01M) || AgNO3 (1.0M) | Ag (s)
Answer:
Ag(s) | AgNO3 (0.01M) || AgNO3 (1.0) Ag(s)
0.80 -
0.80 – 0.0591
0.80 – 0.051 * 1
= 0.7409V
20. (a) Give two differences between macromolecular colloids and associated colloids.
(b) Explain the term dialysis. How can it be increased?
Answer:
(a)
Macromolecular
Associate colloids
Macromolecular colloids are by dispersing macromolecules having colloidal size in proper dispersion.
Associated colloids are formed by aggregation of particles at higher concentration to colloidal range.
Example protein, starch colloids.
Example micelles.
(b) The main purpose of dialysis is to help patients with impaired renal function. When the kidneys are damaged, they are no longer able to remove waste and excess fluid from the blood stream efficiently. Wastes such as nitrogen and creatinine build up in the blood stream.
21. Give reason :
(a) H3PO4 is triprotic acid but H3PO3 is diprotic acid. Why?
(b) NCl3 and PCl3, are hydrolysed differently. Why?
Answer:
(a) H3PO3 is a triprotic acid because it has 2P―OH bonds and 1P―H bonds. H3PO4 contains 3P―OH bonds therefore H3PO4 is a triprotic acid.
(b) In NCl3, nitrogen and chlorine have similar electro-negativities resulting in non-polar bonds. Nitrogen doesn’t have empty d-orbitals so hydrolysis takes place with donation of a lone pair of electrons by nitrogen to the hydrogen atom by water.
NCl3 + H2O → NH3 + 3HOCl
In PCl3, phosphorus is less electronegative than Cl. They form polar bonds, so the positive polar charge on phosphorus attacks the lone pair of electrons.
PCl3 + 3H2O → H3PO3 + 3HCl
22. (a) Why phenols are acidic in nature?
(b) Explain the mechanism of the following reaction:-
Answer:
(a) Phenol is a very weak acid. The position of equilibrium lies to the left. Phenol can lose a hydrogen ion because the phenoxide ion formed is stabilised to some extent. The negative charge on the oxygen atom is delocalised around the ring. The more stable the ion.
(b) Diagram to show mechanism of the reaction:-
Step 1:-
Step 2:-
23. (a) What are Etard Reaction and Gattermann Koch Reaction ? Give one example of each.
(b) Aldehydes are more reactive towards nucleophillic addition reactions than Ketones. Justify.
Answer:
(a) Etard reaction:-
Etard reaction is used to produce benzaldehyde from toluene. Reagent used is CrO2Cl2.Toluene can be oxidised to benzaldehyde.
Gattermann Koach reaction:-
(b) This is because both show steric and electronic effect. In aldehydes, the relatively small hydrogen atom is attached to one side of the carbonyl group while a larger R group is affixed to the other side.
OR
23. (a) What are Claisen-Schmidt condensation and Kolbe's Reaction ? Give one example of each.
(b) NH3 and its derivative do not show nucleophillic addition reactions with aldehydes and ketone in high acidic medium. Justify.
Answer:
(a) Claisen Schmidt Condesation:-
Eg. α –β unsaturated aldehyde.
Kolbe’s Schmidt reaction:-
Eg. in personal care product.
(b) Many nucleophiles like ammonia and derivatives of ammonia can also be added to the carbonyl group of aldehydes and ketones. The reaction of ammonia and its derivatives is reversible and the reaction in the presence of an acid to form aaddtional products. The reaction equilibrium helps with production formation because fast dehydration of the intermediate complex.
Hydrozones of aldehydes and ketones are not prepared in highly acidic medium. In highly acidic medium the protonation of hydrazine decreases in nucleophilic character. Hydrozones of aldehydes and ketones are not prepared in highly acidic medium.
24. (a) Why CIF3 exists but FCl3 does not?
(b) Why ICl3 is more reactive than l2?
(c) Using VBT theory describe the shape of XeO4Answer:
(a) Fluorine differs from the rest of other members because of its small size, high electro-negativity and non-availability of d-orbitals in the valence shell. Fluorine is the most reactive halogen due to its low enthalpy.
(b) Sulphuric acid is an oily and viscous liquid because it is dense, colourless and a highly corrosive liquid most commonly known as hydrogen sulphate.
(c) Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2
OR
24. (a) Why does Fluorine shows anomalous behavior ?
(b) Why sulphuric acid is oily and viscous liquid ?
(c) What happens when Cu reacts with cold dilute HNO3 ?Answer:
(a) Fluorine does not possess d-orbitals, so it can’t expand its octet bond with three chlorine atoms and form FCl3. Chlorine on the other hand has empty d-orbitals and thus it can expand its octet to bond with three fluorine atoms to form ClF3.
(b) ICl3 is more reactive than I2 because I―Cl bond in ICl is weaker than I―I bond in I2.
(c) Xenon has 8 valence e-
Oxygen has 6 valence e-
xe = 4d10 5s2 5p6 5d8 (in ground state)
In excited state:-
These of e- form π bonds with the same oxygen atoms.
Shape of XeO4 :-
In fourth excited, xenon atom has 8 unpaired electrons. Shape of XeO4 is tetrahedral with a bond angle of 1090.
25. (a) Why do Zr and Hf have similar properties ?
(b) What happens when K2Cr2O7 is treated with H2SO4 and Nacl solution?
(c)Transition metals form alloys easily?
Answer:
(a) Due to lanthanoide contraction.
(b) 6NaCl + K2Cr2O7 + H2SO4 → 3Cl2 + Cr2(SO4)3 + 3Na2SO4 + K2SO4 + 7H2O
(sodium chloride) (potassium dichromate) (sulphuric acid) (chlorine) (chromium sulphate) (sodium sulphate) (potassium sulphate) (water)
Sodium chloride reacts with potassium dichromate and sulphuric acid to produce chlorine, chromium sulphate, sodium sulphate, potassium sulphate and water.
Sodium chloride should be solid and heated concentrated sulphuric acid solution.
(c) The atomic radii of transition elements in any series are not much different from each other. They can very easily replace each other in the lattice and form solid solution, an appreciable composition range. Such solutions are called alloys.
OR
25. (a) What happens when K2Cr2O7 is heated strongly?
(b) Transition elements form complexes easily? Justify
(c) Why 5d transition series elements have higher ionization enthalpies than 4d transition series elements?
Answer:
(a) When heated strongly, it decomposes with evolution of oxygen.
4K2Cr2O7→ 4K2CrO4 + 2Cr2O3 + 3O2
(b) Transition elements are d-block elements. They have valence shell configuration of (n-1) d1-10. Because small size and higher nuclear charge, availability of valence d-orbital of suitable energy to accommodate lone pair of electrons donated by ligands.
(c) 5-d elements have high nuclear charge than 4d- elements. Therefore, the outer electrons are attached strongly attached by nucleus in 5d – elements. On the other hand, shielding effect of 4f electron is very poor due to 5d elements.
26. (a) Explain with example SN1 mechanism
(b) Dipole moment of chlorobenzene is lower than that of cyclohexylcholoride. Give reason.
Answer:
(b) Chloro benzene is more electronegative than cyclohexyl chloride. The density of electrons in C―Cl bond of chlorine atom is less than that cyclohexyl chloride. This results into a decrease in the polarity of the C―Cl bond. Hence the dipole moment of chloro benzene is lower than cyclohexyl chloride.
OR
26. How will you convert the following ?
(a) Ethyt bromide to Ethylisocyanide
(b) Isopropylbromide to ProPene
(c) Anitine to Flourobenzene
(d) Chlorobenzene to D.D.T.
(e) Bromoethane to iodoethane.
(f) Chlorobenzene to Aniline.
Answer:
(a) Ethyl bromide + silver cyanide → ethyl isocyanide + silver bromide.
CH₃CH₂-Br + AgCN → CH₃CH₂-NC + AgBr.
(b) Isopropylbromide to Propene:-
(c) Aniline to Flourobenzene:-
(d) Chlorobenzene to D.D.T. :-
(e) Bromoethane to iodoethane :-
CH3CH2Cl + NaI Acetone
CH3CH2I + Nacl(f) Chlorobenzene to Aniline:-
Question paper 2
1. How is benzamide converted into benzylamine?
Answer:
Read more2. The chemical name of Vitamin E is ______________
Answer:
Read more3. Soft soaps are potassium salts of higher fatty acids. True/False
Answer:
Read more4. Out of 1M urea solution and IM KCl solution, which one has higher freezing point ?
Answer:
Read more5. What is Tollen's reagent
Answer:
Read more6. Predict the products in the following reaction :
Answer:
7. What are the units of Rate constant for First Order reaction ?
Answer:
Read more8. The class of drugs used for the treatment of cut or wound is :
(a) Tranquillizers (b) Antiseptics (c) Antihistamins (d) Antipyretic
Answer:
9. Why do transition metals have high enthalpies of atomization ?
Answer:
Read more10. Why does acetylation of -NH, group of aniline reduce its activity ?
Answer:
Read more11. Write two structural differences between DNA and RNA.
Answer:
Read more12. In a metallic oxide, oxide ions are arranged in cubic close packing. One sixth of the tetrahedral voids are occupied by cations P and one third of octahedral voids are occupied by the cation Q.
Deduce the formula of the compound.Answer:
13. Explain Mond's process used for refining of nickel.
Answer:
Read more14. [Fe(CN)6]-3 is low spin complex but [Fe(H2O)6]-3 is high spin complex. Explain.
Answer:
Read more15. For a reaction rate law expression is :
Rate=K[A]1/2 [B]2
Can the reaction be an elementary ? Explain.Answer:
16. What are biodegradable polymers ? Give chemical equation for the preparation of any one biodegradable polymer.
Answer:
Read more17. Give reason :
(a) H3PO4 is triprotic acid but H3PO3, is diprotic acid. Why?
(b) NCI3 and PC3 are hydrolysed differently. Why?Answer:
18. Why phenols are acidic in nature ?
Answer:
19. (a) What are Etard Reaction and Gattermann Koch Reaction ? Give one example of each.
Answer:
Or
(a) What are Claisen-Schmidt condensation and Kolbe's Reaction ? Give one example of each.Answer:
Read more(b) NH, and its derivative do not show nucleophillic addition reactions with aldehydes and ketone in high acidic medium. Justify.
Answer:
20. (a) Analysis shows nickel oxide has the formula Ni0.93 O1.00 What fraction of Ni exists as Ni3+ and Ni2+ ions in given oxide ?
(b) Explain metal deficiency defect due to cation vacancies.Answer:
21. (a) When HgI2 is added to aqueous solution of KI, why there is an increase in osmotic pressure of solution ? Commercially available HCl contains 38% HCl by mass.
Answer:
Read more22. (a) Give two differences between macromolecular colloids and associated colloids.
(b) Explain the term dialysis. How can it be increased ?Answer:
Read more23. (a) Explain Normal or Standard hydrogen electrode.
(b) How much amount of substance is deposited by passing one Faraday of electricity ?Answer:
Or
Calculate the cell potential (EIN) of the following cell at 298K.
Ag(s) | AgNO3 (0.01M) || AgNO3 (1.OM) Ag(sAnswer:
24. (a) Why do Zr and Hf have similar properties?
Answer:
(b) What happens when K2Cr2O7, is treated with H2SO4 and NaCl solution ?
Answer:
(c) Why Transition metals form alloys easily?
Or
Answer:
(a) What happens when K2Cr2O7 is heated strongly ?
Answer:
(b) Transition elements form complexes easily ? Justify
Answer:
Read more(c) Why 5d transition series elements have higher ionization enthalpies than 4d transition series elements ?
Answer:
Read more25. (a) Explain with example Sy mechanism
Answer:
Read more(b) Dipole moment of chlorobenzene is lower than that of cyclohexylcholoride. Give reason.
OrAnswer:
Read moreHow will you convert the following ?
(a) Ethyl bromide to Ethylisocyanide
(b) Isopropylbromide to Propene
(c) Aniline to Flourobenzene
(d) Chlorobenzene to D.D.T.(e) Bromoethane to iodoethane.
(f) Chlorobenzene to Aniline.Answer:
26. (a) Why CIF3 exists but FCl3 does not?
(b) Why ICl3 is more reactive than l2?
(c) Using VBT theory describe the shape of XeO4Answer:
Or
(a) Why does Fluorine shows anomalous behavior ?
(b) Why sulphuric acid is oily and viscous liquid ?
(c) What happens when Cu reacts with cold dilute HNO3 ?Answer:
Read more