Lesson Archives

  1. 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 […]
  2. 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 […]
  3. 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 […]
  4. 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 […]
  5. 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 […]
  6. Page No 388: Question 15.1: A string of mass 2.50 kg is under a tension of 200 N. The length of the stretched string is 20.0 m. If the transverse jerk is struck at one end of the string, how long does the disturbance take to reach the other end? Answer: Mass of the string, […]
  7. Page No 358: Question 14.1: Which of the following examples represent periodic motion? (a) A swimmer completing one (return) trip from one bank of a river to the other and back. (b) A freely suspended bar magnet displaced from its N-S direction and released. (c) A hydrogen molecule rotating about its center of mass. (d) […]
  8. Page No 333: Question 13.1: Estimate the fraction of molecular volume to the actual volume occupied by oxygen gas at STP. Take the diameter of an oxygen molecule to be 3Å. Answer: Diameter of an oxygen molecule, d = 3Å Radius, r = 1.5 Å = 1.5 × 10–8 cm Actual volume occupied by 1 […]
  9. Page No 316: Question 12.1: A geyser heats water flowing at the rate of 3.0 litres per minute from 27 °C to 77 °C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0 × 104 J/g? Answer: Water is flowing […]
  10. Page No 294: Question 11.1: The triple points of neon and carbon dioxide are 24.57 K and 216.55 K respectively. Express these temperatures on the Celsius and Fahrenheit scales. Answer: Kelvin and Celsius scales are related as: TC = TK – 273.15 … (i) Celsius and Fahrenheit scales are related as: … (ii) For neon: […]