KVPY-SA 2016 Chemistry Paper with Solutions

Question 1: One mole of one of the sodium salts listed below, having carbon content close to 14.3% produces 1 mole of carbon dioxide upon heating (atomic mass Na = 23, H = 1, C = 12, O = 16). The salt is

a) C₂H₅COONa
b) NaHCO₃

c) HCOONa
d) CH₃COONa

Answer: (b)

Molecular weight of NaHCO₃ = 23+1+12+48 = 84 g mol^–1

Molecular weight of carbon = 12 g mol^–1

% carbon content in NaHCO₃ = (12/84) x 100 = 14.28%

The C content in other compound is not 14.3%

Question 2: Among formic acid, acetic acid, propanoic acid and phenol, the strongest acid in water is

a) formic acid
b) acetic acid
c) propanoic acid
d) phenol

Answer: (a)

Formic acid is strongest acid

→ Carboxylic acids are more acidic than phenol due to equivalent resonating structure.

E.g.

→ Carboxylic acid is more acidic than phenol and alcohol because conjugate base of a carboxylic acid is stabilized by two equivalent resonance structures in which the negative charge is effectively delocalized between two more electronegative oxygen atoms.

→ Hence, the overall order of acidic strength will be –

Question 3: According to Graham’s Law, the rate of diffusion of CO, O₂, N₂ and CO₂ follows the order:

a) CO = N₂ > O₂ > CO₂

b) CO = N₂ > CO₂ > O₂

c) O₂ > CO = N₂ > CO₂

d) CO₂ > O₂ >CO = N₂

Answer: (a)

Rate of diffusion ∝ 1/√ m, m → molecular weight

Hence, the order of molecular mass → CO₂ > O₂ > CO=NO

Order of diffusion CO= N₂ > O₂ > CO₂

Question 4: The major product formed when 2-butene is reacted with O₃ followed by treatment with Zn/H₂O is

a) CH₃COOH
b) CH₃CHO
c) CH₃CH₂OH
d) CH₂ = CH₂

Answer: (B)

Reaction of 2-butene with O₂ follow as

Question 5: The IUPAC name for the following compound is

a) 2-propylhex-1-ene
b) 2-butylpent-1-ene
c) 2-propyl-2- butylethene
d) Propyl-1-butylethene

Answer: (a)

Solution: (2 propyl hex -1-ene)

Question 6: The major products obtained in the reaction of oxalic acid with conc. H₂SO₄ upon heating are

a) CO, CO₂, H₂O
b) CO, SO₂, H₂O
c) H₂S, CO, H₂O
d) HCOOH, H₂S, CO

Answer: (a)

Reaction of oxalic acid with conc. H₂SO₄ upon heating follows as

Question 7: LiOH reacts with CO₂ to form Li₂CO₃ (atomic mass of Li=7). The amount of CO₂ (in g) consumed by 1g of LiOH is closest to

a) 0.916
b) 1.832
c) 0.544
d) 1.088

Answer: (a)

Reaction of LiOH with CO₂ follows as

Hence, the moles of LiOH = moles of CO₂ × 2

Moles of LiOH = (weight of LiOH)/(molecular wt) = 1/24 = 0.417 moles

Hence, the moles of CO₂= (1/2) x moles of LiOH = 0.0208 moles

Weight of CO₂ = moles x molecular weight = 0.0208 × 44 = 0.916 g

Therefore, the correct option is (A).

Question 8: The oxidation number of sulphur is +4 in

a) H₂S
b) CS₂

c) Na₂SO₄

d) Na₂SO₃

Answer: (d)

Let, the oxidation number of S = X

(i) H₂S → x+2 x(+1) = 0 ⇒ x = –2

(ii) CS₂ → 2x + 1 x (+4) = 0 ⇒ x =-2

(iii) Na₂SO₄ → 2 x(+1)+x+(-2)x4 = 0 ⇒ x = +6

(iv) Na₂SO₃ → 2 x (+1)+x +(-2)x3 = 0 ⇒ x = +4

Question 9: Al₂O₃ reacts with

a) only water
b) only acids
c) only alkalis
d) both acids and alkalis

Answer: (d)

Hint: See the definition and key point of amphoteric oxide.

Al₂O₃ is an amphoteric oxide hence, it reacts with both acid and base as given below

Option (D) is correct.

Question 10: The major product formed in the oxidation of acetylene by alkaline KMnO₄ is

a) Ethanol
b) acetic acid
c) formic acid
d) oxalic acid

Answer: (D)

Question 11: In a closed vessel, an ideal gas at 1 atm is heated from 27°C to 327°C. The final pressure of the gas will approximately be

a) 3 atm
b) 0.5 atm
c) 2 atm
d) 12 atm

Answer: (c)

According to the Gay-Lussac’s law, at constant volume, pressure of gas is directly proportional to the absolute temperature of gas (v,n,R -> constant).

P ∝ T or P = KT

P₁ = T₁ K, P₂ = T₂ K

P₁/P₂ = T₁/T₂

Where, P₁ is initial pressure

P₂ is final pressure

T₁ is initial temperature

T₂ is final temperature

1/P₂ = 300/600

P₂ = 2 atm

Question 12: Among the element Li, N, C and Be, one with the largest atomic radius is

a) Li
b) N
c) C
d) Be

Answer: (a)

Question 13: A redox reaction among the following is

a) CdCl₂ + 2KOH → Cd (OH)₂ + 2KCl
b) BaCl₂ + K₂SO₄ → BaSO₄ + 2KCl
c) CaCO₃ → CaO + CO₂

d) 2Ca + O₂ → 2CaO

Answer: (d)

Redox Reaction ->

Chemical reaction in which oxidation and reduction process takes place simultaneously known as redox reaction.

Hence, it is a redox reaction.

Question 14: The electronic configuration which obeys Hund’s rule for the ground state of carbon atom is

Answer: (a)

Hund’s Rules ->

According to Hund’s rule, in the ground state of an atom/molecules, the electronic configuration with lowest energy, is the one with the highest value of spin multiplicity. This implies that low energy orbital’s are first completely filled and in case of degenerate orbital’s (two or more orbital’s of equal energy), each orbital occupy single electron with same spin

Energy of orbital’s 1S < 2S < 2P

If we see all the options, only C follows the Hund’s law according above definition.

Question 15: The graph that depicts Einstein photoelectric effect for a monochromatic source of frequency above the threshold frequency is

Answer: (c)

Photoelectric effect is the phenomenon of ejection of electron from the surface of a material upon irradiation with light. The ejected electron thus, gives the photo electric current. These electrons can be ejected only by supplying a minimum amount of energy called threshold energy (frequency). Intensity of a monochromatic light is proportional to the number of photons with particular frequency. Since, each photon can abstract one electron at a time therefore, if the photons, the number of photoelectrons in the same proportion. Thus, suggests that above threshold frequency the photoelectric current and light intensity will linearly.

Question 16: In the following reactions, X, Y and Z are

a) X = CH₃Cl; Y = anhydrous AlCl₃; Z = HNO₃ + H₂SO₄

b) X = CH₃COCl; Y = anhydrous AlCl₃; Z = HNO₃ + H₂SO₄

c) X = CH₃Cl; Y = conc. H₂SO₄; Z = HNO₃ + H₂SO₄

d) X = CH₃Cl; Y = dil. H₂SO₄; Z = HNO₃

Answer: (a)

Question 17: 2,3-dibromobutane can be converted to 2-butyne in two-step reaction using

a) (i) HCl and (ii) NaH
b) (i) alcoholic KOH and (ii) NaNH₂

c) (i) Na and (ii) NaOH
d) (i) Br₂ and (ii) NaH

Answer: (b)

Reaction mechanism of conversion of 2,3 dibromo butane to 2 butyne follow as–

Question 18: Given

NO(g) + O₃ (g) → NO₂ (g) + O₂ (g) and Δ H = –198.9 kJ/mol

O₃(g) → 3/2 O₂ (g) and ΔH = –142.3 kJ/mol

O₂(g) → 2O(g) and ΔH = +495.0 kJ/mol

The enthalpy change (Δ H) for the following reaction is

NO (g) + O (g) → NO₂ (g)

a) –304.1 kJ/mol
b) +304.1 kJ/mol
c) –403.1 kJ/mol
d) +403.1 kJ/mol

Answer: (a)

Note: Enthalpy is a state function hence, it depends only on initial and final state, and not on path followed by the function.

Therefore, the correct answer is (A).

Question 19: A 1.85 g sample of an arsenic-containing pesticide was chemically converted to AsO₄^3– (atomic mass of As = 74.9) and titrated with Pb²⁺ to form Pb₃ (AsO₄)₂. If 20 mL of 0.1 M Pb²⁺ is required to reach the equivalence point, the mass percentage of arsenic in the pesticide sample is closest to

a) 8.1
b) 2.3
c) 5.4
d) 3.6

Answer: (c)

Reaction of Pb⁺² with ASO^3-₄ follows as

3Pb⁺² + 2 ASO^3-₄ -> Pb₃ (ASO₄)₂

From above reaction,

Moles of Pb⁺² = (3/2) moles of ASO^3-₄

Moles of ASO^3-₄ = (2/3) moles of Pb⁺²

Morality of Pb⁺² = (moles x1000)/v

Moles of Pb⁺² = (0.1 x 20)/1000 = 2 x 10^-3 moles

Hence, moles of ASO^3-₄ = (2/3) x 2 x 10^-3 = (4/3) x 10^-3 moles

Molecular weight of As = 74.9 g mol^–1

Because, moles = wt/mw, so wt of As = moles x mw = 74.9 x 4/3 x 10^-3

Weight of As = 0.09986g

Therefore, Percentage of As in sample = (0.09986/1.85) x 100 = 5.4%

The correct answer is (C).

Question 20: When treated with conc. HCl, MnO₂ yields gas (X) which further reacts with Ca(OH₂) to generate a white solid (Y). The solid (Y) reacts with dil. HCl to produce the same gas X. the solid Y is

a) CaO
b) CaCl₂

c) Ca(OCl)Cl
d) CaCO₃

Answer: (c)

Following steps are involved in the reaction –

Hence, here solid Y = Ca(OCl) Cl or CaOCl₂

Therefore, the correct answer is (C).