Chemistry Practical II — practice Past Questions

University of Ilorin CHM108: 15 questions.

Topics: Functional Group Analysis and Identification of Unknown Organic Compounds, Preliminary Tests of Organic Compounds, Elemental Analysis of Organic Compounds, Basic Laboratory Techniques and Data Recording, Solubility Tests of Organic Compounds

1. What does it mean if a water-soluble unknown organic compound turns blue litmus paper red?
   1. It is an acidic compound
   2. It is a basic compound
   3. It is a neutral compound
   4. It is an amphoteric compound
2. What is the primary purpose of preparing a derivative of an unknown organic compound?
   1. To determine the exact melting or boiling point for confirmation of identity
   2. To change the physical state of the compound to a gas for analysis
   3. To increase the solubility of the unknown in distilled water
   4. To separate aliphatic compounds from aromatic compounds
3. How do you quickly differentiate between an aliphatic and an aromatic compound in the laboratory?
   1. By performing an ignition test
   2. By reacting it with sodium hydroxide
   3. By measuring its relative density
   4. By testing its solubility in cold water
4. An unknown organic component dissolves in dilute NaOH but does not dissolve in NaHCO₃. What is it likely to be?
   1. A weak acid like a phenol
   2. A strong acid like a carboxylic acid
   3. A base like an amine
   4. A neutral compound like an alcohol
5. Which of the following chemical tests is used to test for unsaturation (presence of double or triple bonds) in organic compounds?
   1. Bromine water test or Baeyer's test
   2. Lassaigne's test
   3. Tollens' test
   4. Iodoform test
6. What is the very first step when identifying an unknown organic compound in a qualitative analysis scheme?
   1. Physical examination (color, odor, state)
   2. Elemental analysis for nitrogen and halogens
   3. Determining the melting or boiling point
   4. Performing a solubility test in various solvents
7. What valuable information does an ignition test provide about an unknown organic compound?
   1. Whether it is highly unsaturated/aromatic or aliphatic
   2. Whether it contains nitrogen or halogens
   3. The exact molecular weight of the compound
   4. Its acidic or basic nature
8. How do you detect the presence of carbon and hydrogen in an unknown organic compound?
   1. By heating the compound with dry copper(II) oxide (CuO)
   2. By fusing the compound with sodium metal
   3. By reacting it with concentrated sulfuric acid
   4. By mixing it with bromine water
9. How can you quickly determine if a water-soluble unknown is an acid or a base using only water and indicator paper?
   1. Dissolve it in water and test the solution with litmus paper
   2. Dissolve it in water and heat to boiling to observe gases
   3. Add water and look for the formation of a precipitate
   4. Mix with water and observe if the container becomes cold
10. Which of the following describes the standard chemical test for a carboxylic acid functional group?
    1. Add sodium bicarbonate (NaHCO₃) and look for effervescence of CO₂
    2. Add bromine water and look for rapid decolorization
    3. Add 2,4-DNPH and look for a yellow-orange precipitate
    4. Add Tollens' reagent and look for the formation of a silver mirror
11. Which of the following chemical tests successfully distinguishes an aldehyde from a ketone?
    1. Tollens' test or Fehling's test
    2. 2,4-DNPH test
    3. Lucas test
    4. Ferric chloride test
12. What is the primary purpose of fusing an unknown organic compound with sodium metal in Lassaigne's test?
    1. To convert covalently bonded elements (N, S, X) into water-soluble ionic sodium salts
    2. To determine if the carbon skeleton is highly branched
    3. To neutralize any acidic functional groups present in the sample
    4. To break down the carbon backbone into carbon dioxide gas
13. During the elemental analysis of an organic compound via Lassaigne’s test, what colour confirms the presence of Nitrogen?
    1. Prussian blue or green
    2. Blood red
    3. Pale yellow
    4. Black
14. Which of the following lists contains four different chemical tests that can be used to positively confirm the presence of an aldehyde?
    1. Tollens' test, Fehling's test, Benedict's test, and Schiff's test
    2. Lucas test, Iodoform test, Bromine water test, and Baeyer's test
    3. Ferric chloride test, Hinsberg test, Carbylamine test, and Azo-dye test
    4. Biuret test, Ninhydrin test, Xanthoproteic test, and Millon's test
15. Which combination best represents four valid techniques for the separation of organic compounds and the different types of chromatography used for identification?
    1. Techniques: Distillation, Sublimation, Crystallization, Extraction. Chromatography: Paper, TLC, Column, Gas
    2. Techniques: Titration, Filtration, Decantation, Ignition. Chromatography: Liquid, Solid, Gas, Plasma
    3. Techniques: Evaporation, Flocculation, Centrifugation, Precipitation. Chromatography: Active, Passive, Neutral, Reactive
    4. Techniques: Melting, Boiling, Freezing, Condensing. Chromatography: Alpha, Beta, Gamma, Delta

Register free to unlock all 15 questions with answers and explanations