Which of the following statements relating to carbon and its compounds are correct? 1. 1-Propyne has three double bonds. 2. The boiling point of acetic acid is higher than methane. 3. Ethanol reacts with sodium metal and produces hydrogen gas. 4. Esters give effervescence on reaction with sodium bicarbonate. Select the answer using the code given below.
- A.1 and 3
- B.2 and 3 only
- C.1 and 2
- D.2, 3 and 4
Correct answer
Explanation
The correct answer is B, 2 and 3 only. Acetic acid boils far above methane, and ethanol gives hydrogen with sodium, while statements 1 and 4 are false.
Propyne (CH3–C≡CH) is an alkyne: it has one carbon–carbon triple bond and no double bonds, so statement 1 is wrong. Acetic acid boils at about 118 °C because its molecules are larger and held together by hydrogen bonds, while methane boils at about −162 °C, so statement 2 is right. Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas (2C2H5OH + 2Na → 2C2H5ONa + H2), so statement 3 is right. Effervescence with sodium bicarbonate is the test for a carboxylic acid, which releases carbon dioxide; esters are neutral and do not react this way, so statement 4 is wrong.
A and C are wrong because they include statement 1. D is wrong because it includes statement 4.
Exam tip: brisk CO2 with NaHCO3 shows an acid such as ethanoic acid; H2 with sodium shows an alcohol or acid.
Practice Questions
View allWhich of the following statements about a fluid at rest in a cup is/are correct? 1. Pressure is same at all the points in the fluid 2. Pressure is exerted on the walls. 3. Pressure exists everywhere in the fluid. Select the correct answer using the code given below :
- A.1 and 2 only
- B.2 and 3 only
- C.1 only
- D.1, 2 and 3
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Read the full explanation →The absolute zero temperature is 0 Kelvin. In °C unit, which one of the following is the absolute zero temperature?
- A.0 °C
- B.-100 °C
- C.-273.15 °C
- D.-173.15 °C
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Read the full explanation →Dinitrogen (N₂) and dioxygen (O₂) are the main constituents of air but they do not react with each other to form oxides of nitrogen because
- A.the reaction requires initiation by a catalyst
- B.oxides of nitrogen are unstable
- C.the reaction is endothermic and requires very high temperature
- D.the stoichiometry of N₂ and O₂ in air is not ideal for the reaction to take place
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Read the full explanation →Hydrogenation of vegetable oils using nickel catalyst is an example of
- A.Substitution reaction.
- B.Elimination reaction.
- C.Addition reaction.
- D.Free-radical polymerization.
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Read the full explanation →A positive charge is moving towards south in a space where magnetic field is pointing in the north direction. The moving charge will experience :
- A.a deflecting force towards north direction.
- B.a deflecting force towards east direction.
- C.a deflecting force towards west direction.
- D.no deflecting force.
Show answer
The charge moves exactly opposite to the field, and a magnetic field exerts no force on a charge moving along its line.
Read the full explanation →