Lesson Archives

  1. Page No 169: Question 7.1: Why are pentahalides more covalent than trihalides? Answer: In pentahalides, the oxidation state is +5 and in trihalides, the oxidation state is +3. Since the metal ion with a high charge has more polarizing power, pentahalides are more covalent than trihalides. Question 7.2: Why is BiH3 the strongest reducing agent amongst […]
  2. Page No 150: Question 6.1: Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method? Answer: If the ore or the gangue can be attracted by the magnetic field, then the ore can be concentrated by the process of magnetic separation. Among the ores mentioned in table 6.1, the ores […]
  3. Page No 127: Question 5.1: Write any two characteristics of Chemisorption. Answer: 1. Chemisorption is highly specific in nature. It occurs only if there is a possibility of chemical bonding between the adsorbent and the adsorbate. 2. Like physisorption, chemisorption also increases with an increase in the surface area of the adsorbent. Question 5.2: Why does physisorption […]
  4. Page No 98: Question 4.1: For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds. Answer: Average rate of reaction  = 6.67 × 10−6 M s−1 Question 4.2: In a […]
  5. Page No 68: Question 3.1: How would you determine the standard electrode potential of the systemMg2+ | Mg? Answer: The standard electrode potential of Mg2+ | Mg can be measured with respect to the standard hydrogen electrode, represented by Pt(s), H2(g) (1 atm) | H+(aq)(1 M). A cell, consisting of Mg | MgSO4 (aq 1 M) as the anode and […]
  6. Page No 37: Question 2.1: Calculate the mass percentage of benzene (C6H6) and carbon tetrachloride (CCl4) if 22 g of benzene is dissolved in 122 g of carbon tetrachloride. Answer: Mass percentage of C6H6  Mass percentage of CCl4 Alternatively, Mass percentage of CCl4 = (100 − 15.28)% = 84.72% Question 2.2: Calculate the mole fraction of […]
  7. Page No 4: Question 1.1: Why are solids rigid? Answer: The intermolecular forces of attraction that are present in solids are very strong. The constituent particles of solids cannot move from their positions i.e., they have fixed positions. However, they can oscillate about their mean positions. This is the reason solids are rigid. Question 1.2: […]
  8. Page No 530: Question 15.1: Which of the following frequencies will be suitable for beyond-the-horizon communication using sky waves? (a) 10 kHz (b) 10 MHz (c) 1 GHz (d) 1000 GHz Answer: (b) Answer: 10 MHz For beyond-the-horizon communication, it is necessary for the signal waves to travel a large distance. 10 KHz signals cannot be radiated efficiently because […]
  9. Page No 509: Question 14.1: In an n-type silicon, which of the following statement is true: (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent atoms are the dopants. (c) Holes are minority carriers and pentavalent atoms are the dopants. (d) Holes are majority carriers and trivalent atoms are the […]
  10. Page No 462: Question 13.1: (a) Two stable isotopes of lithium  and have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium. (b) Boron has two stable isotopes, and. Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is […]