Army Agniveer Written Exam 2023

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There are 15 questions in the NDA Chemistry segment of the exam, which can earn you up to 60 points on the General Ability Test. Here are some advice from experts on how to effectively prepare for the NDA Chemistry Syllabus exam. Therefore, use the information in this post to prepare for the NDA Chemistry curriculum in order to answer 10 or more of the section's questions correctly. On the basis of last year's exam papers, we have additionally covered the miscellaneous NDA Chemistry topics.

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Topics

Chemical Bonding

Chemical bonds are fundamental interactions between atoms that hold compounds together. Covalent and ionic bonds are two common types of chemical bonds that play a crucial role in forming molecules and compounds. While both bonds involve the sharing or transfer of electrons, they exhibit distinct properties and behaviors. This article aims to explore the differences between covalent and ionic bonds, accompanied by a tabular comparison and illustrative examples.

  • Covalent Bond A covalent bond forms when two atoms share electrons to achieve a stable electron configuration. In this bond, atoms share their valence electrons, typically non-metals, to attain a full outer shell. Covalent bonds are characterized by their strength and are commonly found in molecules consisting of identical or similar elements. They result in the formation of molecules with unique properties and can be categorized further into polar and nonpolar covalent bonds.
  • Ionic Bond Ionic bonds arise from the complete transfer of electrons between atoms, typically involving a metal and a nonmetal. In this type of bond, one atom donates electrons (forming a positively charged cation) while another atom accepts electrons (forming a negatively charged anion). The resulting attraction between oppositely charged ions leads to the formation of an ionic compound. Ionic bonds tend to create compounds with high melting and boiling points, as well as good electrical conductivity when dissolved in water.
Comparison Table
Point Of difference Covalent Bond Ionic Bond
Nature of Bond Shared electrons Transferred electrons
Bond Formation Between non-metals Between metals and non-metals
Electron Sharing Equal sharing Complete transfer of electrons
Electronegativity Atoms with Similar electronegativity Atoms with Significant electronegativity
Melting and Boiling Point Generally lower melting and boiling point Generally higher melting and boiling point
Examples H2O (water), CH4 (methane) NaCl (table salt), MgCl2 (magnesium Chloride )
Common Chemical Formula

A chemical formula is a concise and standardized representation of a chemical compound's composition using symbols and subscripts. It provides essential information about the elements present in the compound and their relative ratios. Some of the common examples are-.

No. Chemical Formula Chemical Name
1 H2O Water
2 CO2 Carbon Dioxide
3 NaCl Sodium Chloride
4 C6H12O6 Glucose
5 C12H22O11 Sucrose (Table Sugar)
6 CH4 Methane
7 O2 Oxygen
8 N2 Nitrogen
9 HCl Hydrochloric Acid
10 H2SO4 Sulfuric Acid
11 NH3 Ammonia
12 CH3CH2OH Ethanol
13 H2O2 Hydrogen Peroxide
14 CaCO3 Calcium Carbonate
15 C6H6 Benzene
16 C2H5OH Ethyl Alcohol (Ethanol)
17 C8H18 Octane
18 Fe2O3 Iron(III) Oxide (Hematite)
19 C6H5OH Phenol
20 C2H4O2 Acetic Acid
21 NaOH Sodium Hydroxide
22 HNO3 Nitric Acid
23 C7H6O2 Salicylic Acid
24 H2SO3 Sulfurous Acid
25 CH3COCH3 Acetone
26 H3PO4 Phosphoric Acid
27 H2S Hydrogen Sulfide
28 CH3COOH Acetic Acid
29 HF Hydrofluoric Acid
30 C3H8 Propane
31 Na2CO3 Sodium Carbonate
32 HNO2 Nitrous Acid
33 C2H2 Ethyne (Acetylene)
34 CO Carbon Monoxide
35 NaHCO3 Sodium Bicarbonate
36 Mg(OH)2 Magnesium Hydroxide
37 H2Se Hydrogen Selenide
38 KCl Potassium Chloride
39 SiO2 Silicon Dioxide (Silica)
40 CH3NH2 Methylamine
41 KNO3 Potassium Nitrate
42 C6H5CH3 Toluene
43 H3PO3 Phosphorous Acid
44 Ca(OH)2 Calcium Hydroxide
45 C6H5COOH Benzoic Acid
46 C5H12 Pentane
47 H2CO3 Carbonic Acid
48 CaSO4 Calcium Sulfate
49 CH3Cl Methyl Chloride
50 C4H10 Butane
51 CH3COCCH3 Butanone (Methyl Ethyl Ketone)
52 Na2SO4 Sodium Sulfate
53 C3H6O Acetone
54 C5H5N5O Caffeine
55 C7H8 Toluene
56 C2H4Cl2 Ethylene Dichloride (EDC)
57 C8H10N4O2 Theobromine
58 C6H5N3O4 Nitroglycerin
59 C5H4N4O Guanine
60 C3H7NO2 Isopropyl Nitrite
61 C3H4N2 Propylene Imine
62 C4H4O4 Maleic Acid
63 C3H8O2 Isopropyl Alcohol
64 C8H8O3 Aspirin
65 C4H6N2O3 Creatine
66 C6H5CO2H Benzoic Acid
67 C2H5NO2 Glycine
68 C8H18O Octanol
69 C6H8O7 Citric Acid
70 C2H4Cl2 Ethylene Dichloride (EDC)
71 C5H12O Pentanol
72 C7H16 Heptane
73 C6H4(OH)2 Hydroquinone
74 C6H5COCH3 Acetophenone
75 C4H10O Butanol
76 C2H4O Ethanol
77 C6H5CH2OH Benzyl Alcohol
78 C2H2Cl2 Dichloroethane
79 C5H10O5 Ribose
80 C3H6O2 Propanoic Acid
81 C3H6N6O6 Adenosine Triphosphate (ATP)
82 C4H6O2 Acetic Anhydride
83 C4H6N2O4 Theophylline
84 C3H8O3 Glycerol
85 C5H10N2O3 Thymine
86 C6H5NO2 Nitrobenzene
87 C5H10O4 Xylose
88 C3H4O3 Acetic Acid
89 C5H12N2O2 Urea
90 C6H12O6 Galactose
91 C2H4O2 Acetic Acid
92 C7H8O3 Vanillin
93 C4H6O5 Maleic Acid
94 C5H10O5 Ribose
95 C7H6N2O2 Aniline
96 C8H10O2 Isobutyric Acid
97 C4H8O Tetrahydrofuran
98 C6H14O2 1,6-Hexanediol
99 C6H14O 1-Hexanol
100 C5H10O Cyclopentanol
Laws of Chemical Combination

The laws of chemical combination are fundamental principles that describe the behavior of elements and compounds when they chemically react and combine. These laws lay the foundation for understanding the quantitative relationships between reactants and products in chemical reactions. There are five key laws of chemical combination:

  • Law of Conservation of Mass: This law was formulated by Antoine Lavoisier. The law of conservation of mass states that in a chemical reaction, the total mass of the reactants is equal to the total mass of the products. This means that matter is neither created nor destroyed during a chemical reaction; it is only rearranged from one form to another
  • Law of Multiple Proportions: The law of multiple proportions, proposed by John Dalton, states that when two elements combine to form multiple compounds, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. This law explains the occurrence of different compounds with the same elements in different ratios.
  • Gay-Lussac's Law of Combining Volumes: Gay-Lussac's law of combining volumes states that when gases react with each other at a constant temperature and pressure, the volumes of the reacting gases and the volumes of the products (if gaseous) are in simple whole-number ratios.
  • Avogadro's Law: Avogadro's hypothesis, This law played a crucial role in the development of the concept of Avogadro's hypothesis and the mole concept.formulated by Amedeo Avogadro, states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules
  • Law of Definite Proportions: The law of definite proportions states that a chemical compound always contains the same elements in the same proportion by mass, regardless of the compound's source or method of preparation. This law was established by Joseph Proust and helps in identifying and characterizing compounds based on their consistent composition.
Physical and Chemical Changes

Physical and chemical changes are two fundamental types of transformations that matter can undergo. These changes are distinct in terms of the nature of the alteration and the properties of the substances involved.

    What is a physical change?
    A physical change refers to a transformation that affects the physical properties of a substance without altering its chemical composition. In other words, the identity of the substance remains the same, and only its state or appearance changes. Physical changes are generally reversible, and the substance can often return to its original state.
    Examples of physical changes include:
  • Melting: When solid ice (H2O) melts to become liquid water, the substance remains water, just in a different state.
  • Boiling: The conversion of liquid water into water vapor (steam) involves a change in state, but the chemical composition remains the same.
  • Dissolving : When table salt (NaCl) dissolves in water, it forms a solution, but the chemical composition of salt doesn't change.
  • Crushing : Breaking a piece of chalk into smaller fragments doesn't change the chemical composition of the chalk.
    What is a chemical change?
    A chemical change, also known as a chemical reaction, involves the transformation of one or more substances into new substances with different chemical properties. Chemical changes result in the formation of new chemical bonds and often involve the release or absorption of energy. Once a chemical change occurs, it's usually not easy to revert the substances back to their original forms.
    Examples of chemical changes include:
  • Combustion : When wood burns in the presence of oxygen, it undergoes a chemical reaction to produce carbon dioxide and water vapor.
  • Rusting : The oxidation of iron (Fe) in the presence of oxygen and water(moisture) leads to the formation of iron oxide (rusting).
  • Digestion : The breakdown of food in the stomach involves various chemical reactions that transform complex substances into simpler compounds that the body can absorb.
  • Baking : The baking of bread involves a chemical reaction where the dough rises due to the release of carbon dioxide gas produced by yeast fermentation.