NCERT Solutions

The s block elements  1. What are the common physical and chemical features of alkali metals? 2. Discuss the general characteristics and gradation in properties of alkaline earth metals. 3. Why are alkali metals not found in nature? 4. Find the oxidation state of sodium in 5. Explain why is sodium less reactive than potassium? … Read more

Exercise 14.3 1. For each of the following compound statements first identify the connecting words and then break it into component statements: (i) All rational numbers are real and all real numbers are not complex. (ii) Square of an integer is positive or negative. (iii) The sand heats up quickly in the sun and does … Read more

16. Starting with sodium chloride how would you proceed to prepare (i) sodium metal (ii) sodium hydroxide (iii) sodium peroxide (iv) sodium carbonate? 17. What happens when (i) magnesium is burnt in air (ii) quick lime is heated with silica (iii) chlorine reacts with slaked lime (iv) calcium nitrate is heated ? 18. Describe two … Read more

Exercise 14.4 1. Rewrite the following statements with “if-then” in five different ways conveying the same meaning. If a natural number is off then its square is also odd. Ans. (i) A natural number is odd implies that its square is odd. (ii) A natural is odd only if its square is odd. (iii) For … 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 14.5 1. Show that the statement “If is a real number such that then is 0” is true by (i) direct method (ii) method of contradiction (iii) method of contrapositive. Ans. The given compound statement is of the form “if then ”. R such that (i) Direct method: If we assume that is true … 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

Miscellaneous Exercise 1. Write the negation of the following statements: (i) For every positive real number , the number is also positive. (ii) All cats scratch. (iii) For every real number , either or (iv) There exists a number such that Ans. (i) There exists a positive real number such that is not positive. (ii) … 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