NDA Examination Chemistry (General Ability Test - General Knowledge) Flashcards

24 sample cards from the Chemistry (General Ability Test - General Knowledge) deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. What is a salt, and what type of salt is common table salt?

   A salt is an ionic compound formed when the hydrogen of an acid is replaced by a metal (or formed from acid-base neutralization). Common table salt is sodium chloride (NaCl), formed from the strong acid HCl and the strong base NaOH, so it is neutral.

2. What is oxidation and reduction in terms of oxygen, hydrogen, and electrons?

   Oxidation is gain of oxygen, loss of hydrogen, or loss of electrons. Reduction is loss of oxygen, gain of hydrogen, or gain of electrons. Both occur together in a redox reaction.

3. What is a redox reaction? Identify the oxidizing and reducing agents.

   A redox reaction is one in which oxidation and reduction occur simultaneously. The oxidizing agent gets reduced (gains electrons) and the reducing agent gets oxidized (loses electrons). Example: in 2Mg + O2 -> 2MgO, Mg is reduced (oxidizing agent is O2) and O2 is the oxidizer while Mg is the reducer.

4. What is corrosion and rusting? Give the formula of rust.

   Corrosion is the slow eating up of a metal surface by air, moisture, or chemicals. Rusting is the corrosion of iron forming a reddish-brown layer of hydrated iron(III) oxide, Fe2O3.xH2O, in the presence of oxygen and water.

5. Name the industrial process for manufacturing ammonia and its conditions.

   The Haber process manufactures ammonia (NH3) from nitrogen and hydrogen: N2 + 3H2 -> 2NH3. It uses high pressure (about 200 atm), a temperature of about 450 C, and an iron catalyst.

6. Name the industrial process used to manufacture sulphuric acid.

   The Contact process is used to manufacture sulphuric acid (H2SO4). It involves oxidizing SO2 to SO3 using a vanadium pentoxide (V2O5) catalyst, then dissolving SO3 to form oleum and finally H2SO4.

7. What is the Solvay process used to manufacture?

   The Solvay process is used to manufacture sodium carbonate (washing soda, Na2CO3) from brine (NaCl), ammonia, and carbon dioxide. It is also called the ammonia-soda process.

8. Why is carbon called tetravalent and what is catenation?

   Carbon is tetravalent because it has 4 valence electrons and forms 4 covalent bonds. Catenation is the unique ability of carbon atoms to link with one another forming long chains, branched chains, and rings, which leads to a vast number of carbon compounds.

9. What are the major allotropes of carbon and a key property of each?

   Diamond: hardest natural substance, each carbon bonded to 4 others, non-conductor. Graphite: soft, slippery, good conductor of electricity, each carbon bonded to 3 others. Fullerene (e.g. C60/buckyball): spherical molecular form of carbon.

10. What are hydrocarbons, and how do saturated and unsaturated hydrocarbons differ?

    Hydrocarbons are compounds made of only carbon and hydrogen. Saturated hydrocarbons (alkanes) have only single C-C bonds (e.g. methane CH4). Unsaturated hydrocarbons have double bonds (alkenes, e.g. ethene C2H4) or triple bonds (alkynes, e.g. ethyne C2H2).

11. Give the molecular formulas of methane, ethane, ethene, and ethyne.

    Methane: CH4; Ethane: C2H6; Ethene (ethylene): C2H4; Ethyne (acetylene): C2H2.

12. What are the general formulas of alkanes, alkenes, and alkynes?

    Alkanes: CnH2n+2; Alkenes: CnH2n; Alkynes: CnH2n-2 (where n is the number of carbon atoms).

13. What is the chemical formula and common use of ethanol and methanol?

    Ethanol (C2H5OH) is the alcohol in alcoholic drinks, used as a solvent and fuel additive. Methanol (CH3OH) is highly toxic, used as an industrial solvent and fuel; consumption can cause blindness or death.

14. What are the three primary nutrients supplied by fertilizers, and which element does each provide?

    The three primary nutrients are Nitrogen (N) for leafy growth, Phosphorus (P) for root and flower development, and Potassium (K) for overall plant health and disease resistance. They are referred to as N-P-K fertilizers.

15. Name three common nitrogenous fertilizers.

    Common nitrogenous fertilizers include urea [CO(NH2)2], ammonium nitrate (NH4NO3), ammonium sulphate [(NH4)2SO4], and calcium ammonium nitrate (CAN). Urea has the highest nitrogen content among solid fertilizers (about 46%).

16. What is the difference between a fertilizer and a manure?

    A fertilizer is a man-made (inorganic) chemical substance rich in specific plant nutrients, fast-acting but adds no humus. A manure is a natural organic substance from decomposed plant/animal waste, nutrient-poor per unit but improves soil texture and adds humus.

17. What are the chemical names and formulas of baking soda, washing soda, and bleaching powder?

    Baking soda: sodium hydrogen carbonate, NaHCO3. Washing soda: sodium carbonate decahydrate, Na2CO3.10H2O. Bleaching powder: calcium oxychloride, CaOCl2.

18. What is the chemical name and formula of plaster of Paris, and what is its main use?

    Plaster of Paris is calcium sulphate hemihydrate, CaSO4.1/2H2O. It is used for setting fractured bones in casts, making moulds, and decorative items; it hardens when mixed with water to form gypsum.

19. What are the chief constituents of glass, and what is added to make it heat-resistant?

    Ordinary glass is made chiefly from silica (sand, SiO2), sodium carbonate (soda), and calcium carbonate (limestone). Adding boron oxide produces heat-resistant borosilicate glass (e.g. Pyrex).

20. What is the difference between thermoplastics and thermosetting plastics? Give examples.

    Thermoplastics soften on heating and can be remoulded repeatedly (e.g. polythene, PVC, polystyrene). Thermosetting plastics set permanently on heating and cannot be remoulded once formed (e.g. bakelite, melamine).

21. What are alloys? Name the constituents of brass, bronze, and steel.

    Alloys are homogeneous mixtures of two or more metals (or a metal and a non-metal). Brass = copper + zinc; Bronze = copper + tin; Steel = iron + carbon (stainless steel also contains chromium and nickel).

22. Name the explosive substances TNT, RDX, and gunpowder by their composition or nature.

    TNT is trinitrotoluene, a common military high explosive. RDX (cyclonite) is a powerful high explosive used in bombs. Gunpowder is a low explosive mixture of potassium nitrate (saltpetre), charcoal, and sulphur.

23. What is dynamite and who invented it?

    Dynamite is an explosive made by absorbing nitroglycerine into an inert porous material (like kieselguhr) to make it stable and safe to handle. It was invented by Alfred Nobel.

24. What is the difference between a high explosive and a low (deflagrating) explosive?

    A high explosive detonates with a supersonic shock wave producing a sudden, violent blast (e.g. TNT, RDX, nitroglycerine). A low explosive deflagrates (burns rapidly, subsonic) and is used as a propellant (e.g. gunpowder).

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