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Organic Chemistry Questions and Answers – Combustion of Organic Compounds | Organic Chemistry Multiple Choice Questions and Answers

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Free download in PDF Organic Chemistry Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>

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(1) What is the concentration of carbon dioxide in the atmosphere?
[A] 3.5 x 106 ppm
[B] 1.0 x 102 ppm
[C] 1.6 x 105 ppm
[D] 1.0 x 103 ppm
Answer: 3.5 x 106 ppm
(2) Which of the following reaction has a faster rate of reaction for nascent oxygen atom?

[A] R1 >> R2
[B] R1 > R2
[C] R1 << R2
[D] R1 < R2
Answer: R1 << R2

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(3) Which of the following is not true about combustion of hydrocarbons?
[A] All hydrocarbons react in air to form carbon monoxide and then carbon dioxide
[B] First step is always the reaction between the hydrocarbon and hydroxyl radical
[C] Alkanes, the hydroxyl radical abstracts a hydrogen atom and forms a carbanion
[D] With alkenes and alkynes, the electron-deficient hydroxyl radical adds to the multiple bond
Answer: Alkanes, the hydroxyl radical abstracts a hydrogen atom and forms a carbanion
(4) What is the type of reaction between alkanes and hydroxyl radical?
[A] endothermic
[B] exothermic
[C] isothermal
[D] isochoric
Answer: exothermic
(5) Which of the following statement is incorrect about oxidation number?
[A] Show electron density and about the tendency of an atom or molecule to engage oxidation-reduction reactions
[B] The oxidation number is always given in Roman numerals while the formal charge is always given in numbers
[C] To calculate an oxidation number, it is essential to know which element in a chemical bond is the most electronegative
[D] It cannot be a negative number
Answer: It cannot be a negative number
(6) With respect to enthalpy of combustion which of the following is correct?
[A] ∆Hrxn = Σ∆Hf (product) – Σ∆Hf (reactant)
[B] ∆Hrxn = Σ∆Hf (reactant) – Σ∆Hf (product)
[C] ∆Hrxn = Σ∆Hf (product) + Σ∆Hf (reactant)
[D] ∆Hrxn = 2 Σ∆Hf (product) – Σ∆Hf (reactant)
Answer: ∆Hrxn = Σ∆Hf (product) – Σ∆Hf (reactant)
(7) Equal volumes of C2H2 & H2 are combusted under identical condition. What will be the ratio of heat evolved for C2H2 and H2?

H2 (g) + 1/2 O2(g) → H2O(g), ∆H=-241.8 KJ

C2H2 (g) + 5/2 O2(g) → CO2(g) + H2O(g), ∆H=-1300 KJ

[A] 5.37/1
[B] 1/5.37
[C] 1/1
[D] 2.8/6.1
Answer: 1/5.37
(8) The heat of combustion of carbon is 394 KJ/mol. What will be the heat evolved in combustion of 6.023 x 1022 atoms of carbon?
[A] 64.7 KJ
[B] 39.4 KJ
[C] 42.4 KJ
[D] 91.6 KJ
Answer: 39.4 KJ
(9) The value ∆H transition of C (graphite) → C (diamond) is 1.9 kJ/mol at 25℃ entropy of graphite is higher than entropy of diamond. This implies that?
[A] C(diamond) is more thermodynamically stable then C (graphite) at 25℃
[B] C(graphite) is more thermodynamically stable than C (diamond) at 25℃
[C] diamond will provide more heat on complete combustion at 25℃
[D] ∆Gtransition of C (diamond) → C (graphite) is -ve
Answer: ∆Gtransition of C (diamond) → C (graphite) is -ve
(10) Which of the following is the slow, low-temperature, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel?
[A] Rapid combustion
[B] Turbulent combustion
[C] Spontaneous combustion
[D] Smouldering
Answer: Smouldering

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