WBJEE 2016 Chemistry paper with simple and understandable solutions are provided on this page. The PDF form of the solutions is also available here for download. Practising previous years’ questions will help the candidates get familiar with the pattern of the question paper and gain confidence in solving the problems. Students are advised to download the WBJEE 2016 Chemistry paper and practise offline during their study hours.
Question 1: Consider the following compounds:
Solution:
Answer: b
Those compounds will easily form a precipitate with AgNO3 in which the conjugate formed is stable.
In option L, we can see that the compound formed is aromatic in nature i.e. contains
(4n + 2)π conjugation so is stable.
This compound is stable since it is aromatic.
Question 2: Consider the following nuclear reactions
Solution:
Answer: b
Nuclear reaction is:-
Therefore, Number of neutrons in L = 230 – 36
= 144
Question 3: Of the following atoms, which one has the highest n/p ratio?
Solution:
Answer: d
Highest n/p ratio
So, the highest n/p ratio is of N16
Question 4: The spin-only magnetic moment of [CrF6]4– (atomic number of Cr is 24) is
Solution:
Answer: d
Question 5: Among the following groupings, which one represents the set of iso-electronic species?
Solution:
Answer: c
Two or more molecular entities are as iso-electronic if they have the same number of valance electrons and same structure i.e. number and connectivity of atoms.
Here we can see that CO, NO+, CN–, C22_
All have 14 electrons each.
Carbon has 6 electrons, oxygen has 8 electrons, nitrogen has 7 electrons.
Question 6: In the complex ion [Cu(CN)4]3– the hybridization state, oxidation state and number of unpaired electrons of copper are respectively
Solution:
Answer: b
Hybridization = sp3
Oxidation state of Cu = +1
Number of unpaired electrons = 0.
Question 7: The maximum number of 2p electrons with electronic spin =-1/2 are
Solution:
Answer: d
The maximum electrons which can be accommodated in p-orbital is 6 electrons.
Three electrons have +1/2 spin and other three have –1/2 spin.
So, a maximum electron in 2p with a spin –1/2 is 3.
Question 8: For N3– > O2– > F– and Na+, the order in which their ionic radii varies is
Solution:
Answer: a
N3–, O2–, F–, Na+ all have the same number of valance electrons. So, these species are isoelectronic and we know, as atomic number increases. Nuclear attraction increase, hence the order of ionic radii will be
N 3– > O2– > F– > Na+
Question 9: Assign the Bravais lattice type of the following unit cell structure.
Solution:
Answer: c
By seeing the given structure. We can conclude that a = b ≠ c and all angles are 90° i.e.
α = β = γ = 90°
And it is body centred lattice i.e. the Bravais notation is I.
Therefore, Bravais lattice is Tetragonal-I.
Question 10: The equilibrium constant for the reaction N2+3H2
Solution:
Answer: b
Given: N2+3H2
equilibrium constant = k
Multiplying equation by 2, we get
2N2+6H2
If equation is multiplied by 2 then k will be squared K2
Or
N2 + 3H2
Now
2N2+6H2
Question 11: Which of the following is the correct option for free expansion of an ideal gas under adiabatic condition?
Solution:
Answer: c
For the free expansion of real gas, the opposing force is zero, and when opposing force is zero then work done = 0
We, know the equation
ΔU = q + w
If w= 0 then ΔU = q
But the process is adiabatic hence q = 0
Therefore, q = 0, T = 0, w = 0
Question 12: 75% of a first order reaction was completed in 32 min. When would 50% of the reaction complete?
Solution:
Answer: b
Question 13: Pressure (P) vs. density (D) curve for an ideal gas at two different temperatures T1 and T2 is shown below.
Solution:
Answer: a
As we know,
Ideal gas equation is PV = nRT
So,
PM = dRT
P ∝ d.T
So, T1 > T2
Question 14: Which of the following compounds is least effective in precipitating Fe(OH)3 Solution:?
Solution:
Answer: c
Fe(OH)3 is positively charged Solution: charge of Br– anion is least and so KBr is least effective in coagulating Fe(OH)3 Solution:
Also, for coagulating positive charged Solution: negatively charged Solution is required. More the negative charge, more easily the coagulation will take place.
Question 15: Which statement is incorrect?
Solution:
Answer: (a,c,d)
Three options are incorrect.
Borazine is B3N3H6 and its structure is not like that of graphite.
[Al6O18] –18 contain tetrahedral units.
Question 16: Which one of the following does not produce O2 as the only gaseous product on heating?
Solution:
Answer: a
We can find out the answer by writing heating equations of compounds.
Therefore, we can observe that when lead nitrate is heated it will give NO2 gas along with O2 gas.
Question 17: Which of the following is true in respect to adsorption?
Solution:
Answer: b
For adsorption process
∆G < 0, ∆H < and ∆S < 0
Question 18: Which property that polyacetylene exhibit is unusual for an organic polymer?
Solution:
Answer: a
Due to the conjugation, it can conduct electricity.
The structure of polyacetylene is shown:
Question 19: Which statement is incorrect about complexes formed by the lanthanoids?
Solution:
Answer: d
The statement aqua ions typically 6-coordinate is incorrect, for example, the coordination number for [Ln(H2O)n]3+ in aqueous solution is thought to be 9 for the early lanthanoids and for the later, smaller numbers of the series.
Question 20: In the alumino-thermite process, aluminium acts as
Solution:
Answer: a
Some metal oxides cannot be reduced satisfactorily by carbon. For them, aluminium which is a more reactive metal is used. The process is called thermic process or alumino-thermic process since this process is only for those metals that can’t be reduced by carbon. Therefore, aluminium is used in place of carbon atoms and it acts as a reducing agent.
Aluminium reduces oxides of metals like Fe/Cr/Mn at elevated temperature.
2Al + Fe2O3
Question 21: Consider the following reaction: 6NaOH + 3Cl2
Solution:
Answer: a
Sodium hydroxide reacts with chlorine gives sodium chloride, sodium chlorate and water molecules as the products. The chemical reaction can be written as:
6NaOH + 3Cl2
(A)
So, the compound (A) is NaClO3
Let the oxidation state of chlorine is x.
The oxidation state of Cl in NaClO3
(+1) + (x) + 3(–2) = 0
x = 6 –1
x = +5
Oxidation number of chlorine is +5.
Question 22: A sudden large difference between the values of second and third ionization energies of elements would be associated with which of the following electronic configurations?
Solution:
Answer: b
After removal of two electrons from 1s2, 2s2, 2p6, 3s2 we get stable noble gas (Ne) configuration. On removing one more electron in this completely filled octet, a high amount of energy required. So there is a large difference between 2nd ionization energy and 3rd ionization energy for this configuration.
Question 23: Na2O2 is produced in the reaction between H2O2 and NaOH. Here, the role of H2O2 is
Solution:
Answer: b
It is an acid-base reaction in which hydrogen peroxide act as acid to react with sodium hydroxide (base) to produce sodium peroxide and water.
Question 24: Amongst the following compounds, the one which would not form a white precipitate with ammoniacal silver nitrate solution is
Solution:
Answer: b
Only terminal alkynes having acidic hydrogen to react with ammoniacal silver nitrate solution known as Tollen’s reagent.
In the given options, CH3≡CCH3 does not have any acidic hydrogen to react with an ammoniacal silver nitrate solution
Question 25: m-dinitrobenzene can be converted to m-nitroaniline by reduction with:
Solution:
Answer: c
Selective reduction of m-nitro benzene to form m-nitroaniline is done by ammonium sulphide. In this reaction out of two nitro groups, only one –NO2 group is reduced.
Question 26: The correct IUPAC name of H3C – C(CH3)2 – CH = CH2 is :
Solution:
Answer: c
The correct IUPAC name of H3C–C(CH3)2–CH=CH2 is 3,3-dimethyl but-1-ene.
Question 27: Which combination of reagents used in the indicated order will give m-nitropropyl benzene from benzene?
2) CH3CH2CH2/AlCl3
2) conc. HNO3/conc. H2SO4
2) conc. HNO3/conc. H2SO4
3) H2NNH2/NaOH
2) CH3CH2COCl/AlCl3
3) H2NNH2/NaOH
Solution:
Answer: c
Correct order to form m-nitropropyl benzene from benzene:
Question 28: Which of the statement (A) - (D) about the reaction profile below is false?
Solution:
Answer: b
The potential energy diagram shows the lower activation energy of a hypothetical reaction in the second step.
The rate of reaction depends on the activation energy; lower activation energy means that a larger number of molecules will have sufficient energy to undergo an effective collision.
Hence, the second step is not a rate-determining step, it is a fast step due to low activation energy.
Question 29: Which of the following is the major product when one mole of propanone and two moles of benzaldehyde react in presence of a catalytic amount of NaOH?
Solution:
Answer: d
This reaction is an example of aldol condensation reaction and is given by aldehydes or ketones having α-H atom to give β-hydroxy aldehyde.
Question 30: For the following anion,
the resonance structure that contributes most is
Solution:
Answer: a
Resonance hybrid (A) is more stable than (B)
Option c and d is least stable because of the positive charge on the electronegative oxygen atom.
Question 31: The major product obtained upon treatment of
with NaNH2 and liquid NH3 is
Solution:
Answer: c
Question 32: Which structure for XeO3 and XeF4 is consistent with the VSEPR model?
Solution:
Answer: a
Xe has electronic configuration [Kr]5s2 5p6.
In the case of XeF4, the structure will be square planar. There are four pairs of bonding electrons and two lone pair in the molecule. Two lone pairs will be opposite each other to maintain symmetry.
XeO3 has trigonal pyramidal geometry with asymmetric charge distribution on central atom. There are three pairs of bonding electrons and one lone pair in the molecule.
Question 33: If CO2 gas is passed through 500 ml of 0.5 (M) Ca(OH)2, the amount of CaCO3 produced is of the value
Solution:
Answer: d
CO2 + Ca(OH)2
Given, volume of Ca(OH)2 = 500 mL
Concentration of Ca(OH)2 = 0.5 M
Moles of Ca(OH)2 = Volume(v) × concentration
=[(500x0.5)/1000] = 0.25 mole
1 mole Ca(OH)2 gives 1 mole CaCO3
0.25 mole Ca(OH)2 gives =(1/1) × 0.25 mole CaCO3 = 0.25 mole CaCO3
Mass of CaCO3 = mole × molar mass {Therefore, Molar mass of CaCO3 is 100 g/mole}
= 0.25 mole × 100 g/mole = 25 g
Question 34: The emf of a Daniel cell at 298 K is E1. The cell is Zn|ZnSO4 (0.01M) || CuSO4 (1M) | Cu When the concentration of ZnSO4 is changed to 1M and that of CuSO4 to 0.01M, the emf changes to E2. The relationship between E1 and E2 will be
Solution:
Answer: c
Zn|ZnSO4(0.01m)||CuSO4(1m)|Cu
According to the Nernst equation
Question 35: Which reaction is not appropriate for the synthesis of the following?
Solution:
Answer: d
Question 36: Which of the following statements are correct with reference to the isoelectric point of alanine?
Solution:
Answer: (a,b,d)
At the isoelectric point, the amino acid exists as zwitterion to the maximum ion concentration.
A zwitterion is a dipolar ion, i.e.
For amino acids that have no ionisable side chain, the pI value is the average of its two pKa’s. If the amino acid has an ionisable side chain, the pI value is the average of the pKa’s of similarly ionisable groups.
Alanine has a net positive charge at pH below the isoelectric point.
Question 37: Consider the proposed mechanism for the destruction of ozone in the stratosphere?
O3 + Cl
ClO + O3
Which of the statements about the mechanism is/are correct?
Solution:
Answer: (a,c)
(A) Electronic configuration of 24Cr: [Ar] 3d5 4s1, Due to extra stability.
(B)Magnetic quantum number may have a negative value.
When l = 2, m = –2, –1, 0, +1, +2
(C)Silver atoms have atomic number 47.
Question 38: Which of the following statements(s) is (are) correct?
Solution:
Answer: (a,b,c)
Electronic configuration 47Ag: 1s22s22p63s23p63d104s24p6 4d105s1
So, 23 electrons have a spin of one type and 24 of the opposite type.
In HN3, the oxidation state of N is -1/3.
Question 39: Equal quantities of electricity are passed through 3 voltmeters containing FeSO4, Fe2(SO4)3 and Fe(NO3)3. Consider the following statement:
(1) The amounts of iron deposited in FeSO4 and Fe2(SO4)3 are equal
(2) The amount of iron deposited in Fe(NO3)3 is 2/3rd of the amount deposited in FeSO4
(3) The amount of iron deposited in Fe2(SO4)3 and Fe(NO3)3 are equal
Solution:
Answer: (b,d)
1.FeSO4
Fe2+ + 2e–
Therefore, 2F charge is needed for 1 mole deposition of Fe.
2. Fe2(SO4)3
Fe3+ + 3e–
3F
2F charge is needed for (2/3) mole deposition of Fe.
3. Fe(NO3)3
Fe3+ + 3e–
3F
2F charge is needed for 2/3 mole deposition of Fe.
Hence, the correct option is B & D.
Question 40: Which of the following statements are correct for the following isomeric compounds I and II?
Solution:
Answer: (a,b,c)
Enantiomers: non-super imposable non-mirror images are enantiomers. So, compound I and II are enantiomers.
Compound I and II are optically active due to absence of plane of symmetry.
Compound I is D-alanine while II is L-alanine