CBSE

Exercise 15.3 1. From the data given below state which group is more variable, A or B: Ans. Group A Mean = = 45 – 0.4 = 44.6 Standard deviation = = = = 15.09 Group B Mean = = 45 – 0.4 = 44.6 Standard deviation = = = = 15.61 2. From the … Read more

20. What happens when (a) Borax is heated strongly, (b) Boric acid is added to water, (c) Aluminium is treated with dilute NaOH, (d) is reacted with ammonia? 21. Explain the following reactions (a) Silicon is heated with methyl chloride at high temperature in the presence of copper; (b) Silicon dioxide is treated with hydrogen … Read more

Exercise 12.1 1. A point is on the axis. What are its coordinates and coordinates? Ans. We know that coordinates of any point on the axis will be Therefore, coordinate and coordinate of the point are zero. 2. A point is on XZ-plane. What can you say about its coordinate? Ans. We know that coordinates … Read more

Miscellaneous Exercise 1. The mean and variance of eight observations are 9 and 9.25 respectively. If six of the observations are 6, 7, 10, 12, 12 and 13, find the remaining two observations. Ans. Let two required observations be and Then, According to question, ……….(i) Also ……….(ii) When then on solving and we get and … Read more

THE p -BLOCK ELEMENTS  1. Discuss the pattern of variation in the oxidation states of (i) B to Tl and (ii) C to Pb. 2. How can you explain higher stability of as compared to? 3. Why does boron trifluoride behave as a Lewis acid? 4. Consider the compounds,. How will they behave with water? … Read more

Exercise 12.2 1. Find the distance between the following pairs of points: (i) (2, 3, 5) and (4, 3, 1) (ii) and (iii) and (iv) and Ans. (i) Let A (2, 3, 5) and B (4, 3, 1) be two points, then AB = = = units (ii) Let A (–3, 7, 2) and B … Read more

Exercise 16.1 In each of the following exercises 1 to 7, describe the sample space for the indicated experiment. 1. A coin is tossed three times. Ans. S = {HHH, HHT, HTH, THH, TTH, HTT, TTT} 2. A die is thrown two times. Ans. S = {(1, 1), (1, 2), (1, 3), (1, 4), (1, … Read more

21.Discuss the chemistry of Lassaigne’s test. 22. Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method and (ii) Kjeldahl’s method. 23. Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound. 24. Explain the principle of paper chromatography. 25. Why is nitric acid … Read more

Exercise 12.3 1. Find the coordinates of the point which divides the line segment joining the points and in the ratio: (i) 2: 3 internally, (ii) 2: 3 externally. Ans. (i) Let P be any point which divides the line segment joining points A and B in the ratio 2: 3 internally. Then Therefore, Coordinates … Read more

Exercise 16.2 1. A die is rolled. Let E be the event “die shows 4” and F be the event “die shows even number”. Are E and F mutually exclusive? Ans. When a die is rolled, then S = {1, 2, 3, 4, 5, 6} E: die shows 4 = {4} and F: die shows … Read more

ORGANIC CHEMISTRY – SOME BASIC PRINCIPLES AND TECHNIQUES  1. What are hybridisation states of each carbon atom in the following compounds? 2. Indicate the bonds in the following molecules: 3. Write bond line formulas for: Isopropyl alcohol, 2,3-Dimethyl butanal, Heptan-4-one. 4. Give the IUPAC names of the following compounds: (a) (b) (c) (d) (e) (f) … Read more

Miscellaneous Exercise 1. Three vertices of a parallelogram ABCD are A B and C Find the coordinates of the fourth vertex. Ans. Let D be the fourth vertex of parallelogram ABCD. Since, the diagonals of a parallelogram bisect each other. Therefore, the mid-point of AAAC and BD coincide. Coordinates of mid-point of AC = = … Read more

Exercise 16.3 1. Which of the following cannot be valid assignment of probabilities for outcomes of sample space S = Assignment (a) 0.1 0.01 0.05 0.03 0.01 0.2 0.6 (b) (c) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 (d) –0.1 0.2 0.3 0.4 –0.2 0.1 0.3 (e) Ans. (a) Here probability of each outcome is … Read more

HYDROCARBONS1.How do you account for the formation of ethane during chlorination of methane? 2. Write IUPAC names of the following compounds: a. b. c. d. e. f. g. 3.For the following compounds, write structural formulas and IUPAC names for all possible isomers having the number of double or triple bond as indicated: (a) (one double … Read more