Lesson Archives

  1. Page No 305: Question 10.1: What are the common physical and chemical features of alkali metals? Answer: Physical properties of alkali metals are as follows. (1) They are quite soft and can be cut easily. Sodium metal can be easily cut using a knife. (2) They are light coloured and are mostly silvery white in appearance. (3) They […]
  2. Page No 288: Question 9.1: Justify the position of hydrogen in the periodic table on the basis of its electronic configuration. Answer: Hydrogen is the first element of the periodic table. Its electronic configuration is [1s1]. Due to the presence of only one electron in its 1s shell, hydrogen exhibits a dual behaviour, i.e., it resembles […]
  3. Page No 272: Question 8.1: Assign oxidation numbers to the underlined elements in each of the following species: (a) NaH2PO4 (b) NaHSO4 (c) H4P2O7 (d) K2MnO4 (e) CaO2 (f) NaBH4 (g) H2S2O7 (h) KAl(SO4)2.12 H2O Answer: (a)  Let the oxidation number of P be x. We know that, Oxidation number of Na = +1 Oxidation number of H = +1 Oxidation number […]
  4. Page No 224: Question 7.1: A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased. a) What is the initial effect of the change on vapour pressure? b) How do rates of evaporation and condensation change initially? c) What happens when […]
  5. Page No 182: Question 6.1: Choose the correct answer. A thermodynamic state function is a quantity (i) used to determine heat changes (ii) whose value is independent of path (iii) used to determine pressure volume work (iv) whose value depends on temperature only. Answer: A thermodynamic state function is a quantity whose value is independent […]
  6. Page No 152: Question 5.1: What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C? Answer: Given, Initial pressure, p1 = 1 bar Initial volume, V1 = 500 dm3 Final volume, V2 = 200 dm3 Since the temperature remains constant, the final pressure (p2) can be calculated using Boyle’s law. According to […]
  7. Page No 129: Question 4.1: Explain the formation of a chemical bond. Answer: A chemical bond is defined as an attractive force that holds the constituents (atoms, ions etc.) together in a chemical species. Various theories have been suggested for the formation of chemical bonds such as the electronic theory, valence shell electron pair repulsion […]
  8. Page No 92: Question 3.1: What is the basic theme of organisation in the periodic table? Answer: The basic theme of organisation of elements in the periodic table is to classify the elements in periods and groups according to their properties. This arrangement makes the study of elements and their compounds simple and systematic. In […]
  9. Page No 65: Question 2.1: (i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass and charge of one mole of electrons. Answer: (i) Mass of one electron = 9.10939 × 10–31 kg Number of electrons that weigh 9.10939 × 10–31 kg = 1 Number of electrons that will weigh 1 […]
  10. Page No 22: Question 1.1: Calculate the molecular mass of the following: (i) H2O (ii) CO2 (iii) CH4 Answer: (i) H2O: The molecular mass of water, H2O = (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen) = [2(1.0084) + 1(16.00 u)] = 2.016 u + 16.00 u = 18.016 = 18.02 u […]