Ozonolysis of but-2-ene followed by treatment with zinc and water gives ____.
Correct answer B. Two molecules of ethanal
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MDCAT ECAT Chemistry MCQs
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- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
To obtain ethanal rather than ethanoic acid when oxidising ethanol with acidified dichromate, which condition is used?
Correct answer C. Distil off the aldehyde as soon as it forms
How is methanal manufactured industrially?
Correct answer A. By passing methanol vapour and air over a heated silver or copper catalyst
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In the addition of HCN to ethanal, why is a small amount of base added?
Correct answer D. To produce CN⁻ ions, the actual nucleophile
In acid-catalysed nucleophilic addition to a carbonyl compound, what is the first step?
Correct answer C. Protonation of the carbonyl oxygen
In the esterification of ethanol with ethanoic acid, what is the main role of concentrated H₂SO₄?
Correct answer A. It acts as a catalyst and absorbs the water formed
Why does ethanol (M = 46 g/mol) boil at a much higher temperature than propane (M = 44 g/mol)?
Correct answer C. Ethanol molecules form hydrogen bonds with one another
Why is phenol a stronger acid than ethanol?
Correct answer A. The phenoxide ion is stabilised by delocalisation of its charge into the benzene ring
What is observed when aqueous bromine is added to phenol solution at room temperature?
Correct answer A. The bromine is decolourised and a white precipitate forms
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Phenol reacts with dilute nitric acid at room temperature to give mainly ____.
Correct answer B. A mixture of 2-nitrophenol and 4-nitrophenol
Which reagent gives a violet colour with phenol but no colour with ethanol?
Correct answer A. Neutral iron(III) chloride solution
A compound dissolves in aqueous NaOH but does not release CO₂ with NaHCO₃. Which compound fits this behaviour?
Correct answer B. Phenol
How does the OH group affect electrophilic substitution in the benzene ring of phenol?
Correct answer D. It activates the ring and directs to the 2- and 4-positions
Which alcohol gives a yellow precipitate of triiodomethane when warmed with iodine and aqueous NaOH?
Correct answer B. Propan-2-ol
In the fermentation of glucose to ethanol by yeast, which enzyme complex converts glucose into ethanol and carbon dioxide?
Correct answer B. Zymase
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What mass of ethanol can be obtained from the complete fermentation of 90 g of glucose (M = 180 g/mol, ethanol M = 46 g/mol)?
Correct answer A. 46 g
Take molar volume = 22.4 dm³/mol. What volume of hydrogen at STP is produced when 0.20 mol of ethanol reacts with excess sodium?
Correct answer C. 2.24 dm³
What mass of 2,4,6-tribromophenol (M = 331 g/mol) forms when 9.4 g of phenol (M = 94 g/mol) reacts completely with bromine water?
Correct answer D. 33.1 g
How many moles of Br₂ are needed to convert 0.050 mol of phenol completely into 2,4,6-tribromophenol?
Correct answer B. 0.15 mol
Take C = 12, H = 1, O = 16. What is the percentage by mass of oxygen in ethanol, C₂H₅OH?
Correct answer B. 34.8%