Use Mendeleev’s periodic table to predict
[question] Question. Use Mendeleev’s periodic table to predict the formulae for the oxides of the following elements: K, C, Al, Si, Ba. [/question] [solution] solution: Limitations of Newlands’ law of octaves: $\mathrm{K}$ is in group 1. Therefore, the oxide will be $\mathrm{K}_{2} \mathrm{O}$. $\mathrm{C}$ is in group 4 . Therefore, the oxide will be $\mathrm{CO}_{2}$. $\mathrm{Al}$ is in group $3 .$ Therefore, the oxide will be $\mathrm{Al}_{2} \mathrm{O}_{3}$. $\mathrm{Si}$ is in group 4. The...
Read More →Read again the extracts from Nehru's speech
[question] Question. Read again the extracts from Nehru's speech “Tryst with Destiny” and answer the following: (a) Why did Nehru use the expression “not wholly or in full measure” in the first sentence? (b) What pledge did he want the makers of the Indian Constitution to take? (c) “The ambition of the greatest man of our generation has been to wipe every tear from every eye”. Who was he referring to? [/question] [solution] Solution: (a) Nehru used the term ‘not wholly or in full measure’ becaus...
Read More →Match the following leaders with their roles in the making of the Constitution:
[question] Question. Match the following leaders with their roles in the making of the Constitution: [/question] [solution] Solution: [/solution]...
Read More →$\mathrm{Na}^{+}$has completely filled $\mathrm{K}$ and $\mathrm{L}$ shells. Explain.
[question] Question. $\mathrm{Na}^{+}$has completely filled $\mathrm{K}$ and $\mathrm{L}$ shells. Explain. [/question] [solution] Solution: An atom of Na has a total of 11 electrons. Its electronic configuration is $2,8,1 .$ But, $\mathrm{Na}^{+}$ion has one electron less than Na atom i.e., it has 10 electrons. Therefore, 2 electrons go to $\mathrm{K}$-shell and 8 electrons go to $\mathrm{L}$-shell, thereby completely filling $\mathrm{K}$ and $\mathrm{L}$ shells. [/solution]...
Read More →Which of these is a provision that a democratic constitution does not have?
[question] Question. Which of these is a provision that a democratic constitution does not have? (a) Powers of the head of the state (b) Name of the head of the state (c) Powers of the legislature (d) Name of the country [/question] [solution] Solution: (b) Name of the head of the state [/solution]...
Read More →What were the limitations
[question] Question. What were the limitations of Newlands’ Law of Octaves? [/question] [solution] solution: (i) It was not applicable throughout the arrangements. It was applicable up to calcium only. (ii) Those elements that were discovered after Newlands’ octaves did not find a place in Newlands table. (iii) The position of cobalt and nickel in the group of the elements containing F and Cl of different properties could not be explained. (iv) Placing of iron far away from cobalt and nickel, wh...
Read More →Divide the polynomial p(x) by the polynomial
[question] Question. Divide the polynomial p(x) by the polynomial g(x) and find the quotient and remainder in each of the following : (i) $\mathrm{p}(\mathrm{x})=\mathrm{x}^{3}-3 \mathrm{x}^{2}+5 \mathrm{x}-3, \mathrm{~g}(\mathrm{x})=\mathrm{x}^{2}-2$ (ii) $p(x)=x^{4}-3 x^{2}+4 x+5, g(x)=x^{2}+1-x$ (iii) $\mathrm{p}(\mathrm{x})=\mathrm{x}^{4}-5 \mathrm{x}+6, \mathrm{~g}(\mathrm{x})=2-\mathrm{x}^{2}$ [/question] [solution] Solution: Hence, Quotient $q(x)=x-3$ and Remainder $r(x)=7 x-9$ (ii) $x^{2...
Read More →Which of these was the most salient underlying conflict in
[question] Question. Which of these was the most salient underlying conflict in the making of a democratic constitution in South Africa? (a) Between South Africa and its neighbours (b) Between men and women (c) Between the white majority and the black minority (d) Between the coloured minority and the black majority [/question] [solution] Solution: The most salient underlying conflict in the making of a democratic constitution in South Africa was between the white minority and the black majority...
Read More →Explain with examples
[question] Question. Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes. [/question] [solution] Solution: (i) Atomic number The atomic number of an element is the total number of protons present in the atom of that element. For example, nitrogen has 7 protons in its atom. Thus, the atomic number of nitrogen is 7. (ii) Mass numbers The mass number of an element is the sum of the number of protons and neutrons present in the at...
Read More →What were the limitations of Dobereiner’s classification?
[question] Question. What were the limitations of Dobereiner’s classification? [/question] [solution] solution: All known elements could not be classified into groups of triads on the basis of their properties. [/solution]...
Read More →Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves?
[question] Question. Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out. [/question] [solution] solution: Only one triad of Dobereiner's triads exists in the columns of Newlands' octaves. The triad formed by the elements $\mathrm{Li}, \mathrm{Na}$, and $\mathrm{K}$ of Dobereiner's triads also occurred in the columns of Newlands' octaves. [/solution]...
Read More →Here are some false statements.
[question] Question. Here are some false statements. Identify the mistake in each case and rewrite these correctly based on what you have read in this chapter. (a) Leaders of the freedom movement had an open mind about whether the country should be democratic or not after independence. (b) Members of the Constituent Assembly of India held the same views on all provisions of the Constitution. (c) A country that has a constitution must be a democracy. (d) Constitution cannot be amended because it ...
Read More →Explain the mechanism of the cleansing action of soaps.
[question] Question. Explain the mechanism of the cleansing action of soaps. [/question] [solution] solution: A molecule of soap has two dissimilar ends. At one end is the hydrocarbon chain, which is water repellent and the other end is carboxylate anion which is polar end. When soap is dissolved in water, many molecules come together and form a group called micelle. These micelles are formed because their hydrocarbon chains come together and the polar ends are projected outward. When a cloth wi...
Read More →Give a test that can be used to differentiate between
[question] Question. Give a test that can be used to differentiate between butter and cooking oil. [/question] [solution] solution: As cooking oil contains unsaturated hydrocarbons it will undergo addition reaction whereas butter contains saturated hydrocarbons so it will not give addition reaction (hydrogenation) thus hydrogenation reaction can be used. [/solution]...
Read More →Find a quadratic polynomial each with the given numbers as the sum and product of its zeros respectively
[question] Question. Find a quadratic polynomial each with the given numbers as the sum and product of its zeros respectively (i) $\frac{1}{4},-1$ (ii) $\sqrt{2}, \frac{1}{3}$ (iii) $\mathbf{0}, \sqrt{\mathbf{5}}$ (iv) 1,1 $(V)-\frac{1}{4}, \frac{1}{4}$ (vi) 4,1 [/question] [solution] Solution: (i) Required polynomial = $x^{2}-($ sum of zeros $) x+$ product of zeros $=x^{2}-\frac{1}{4} x-1$ $=\frac{1}{4}\left(4 x^{2}-x-1\right)$ (ii) Required polynomial = $x^{2}-($ sum of zeros $) x+$ product of...
Read More →Which of the following hydrocarbons undergo addition reactions ?
[question] Question. Which of the following hydrocarbons undergo addition reactions ? $\mathrm{C}_{2} \mathrm{H}_{6}, \mathrm{C}_{3} \mathrm{H}_{8}, \mathrm{C}_{3} \mathrm{H}_{6}, \mathrm{C}_{2} \mathrm{H}_{2}$ and $\mathrm{CH}_{4}$ [/question] [solution] solution: $\mathrm{C}_{3} \mathrm{H}_{6}$ and $\mathrm{C}_{2} \mathrm{H}_{2}$ because they are unsaturated hydrocarbons compounds. [/solution]...
Read More →Consider the following facts about a country and decide if you would call it a democracy.
[question] Question. Consider the following facts about a country and decide if you would call it a democracy. Give reasons to support your decision. (a) All the citizens of the country have right to vote Elections are held regularly. (b) The country took loan from international agencies. One of the conditions for given loan was that the government would reduce its expenses on education and health. (c) People speak more than seven languages but education is available only in one language, the la...
Read More →What is hydrogenation ?
[question] Question. What is hydrogenation ? What is its industrial application ? [/question] [solution] solution: Unsaturated hydrocarbons add hydrogen in the presence of palladium or nickel. This reaction is called hydrogenation. This reaction is industrially used in the conversion of vegetable oils into vegetable ghee. [/solution]...
Read More →Define valency by taking examples of silicon and oxygen
[question] Question. Define valency by taking examples of silicon and oxygen [/question] [solution] Solution: The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element. If the number of valence electrons of the atom of an element is less than or equal to four, then the valency of that element is equal to the number of valence electrons. For example, the atom of silicon has fo...
Read More →Are the following statements in keeping with democracy as a value?
[question] Question. Are the following statements in keeping with democracy as a value? Why? (a) Father to daughter: I don’t want to hear your opinion about your marriage. In our family children marry where the parents tell them to. (b) Teacher to student: Don’t disturb my concentration by asking me questions in the classroom. (c) Employee to the officer: Our working hours must be reduced according to the law. [/question] [solution] Solution: The first two statements are undemocratic as the girl...
Read More →Write a response to the following arguments against democracy.
[question] Question. Write a response to the following arguments against democracy. (a) Army is the most disciplined and corruption-free organisation in the country. Therefore army should rule the country. (b) Rule of the majority means the rule of ignorant people. What we need is the rule of the wise, even if they are in small numbers. (c) If we want religious leaders to guide us in spiritual matters, why not invite them to guide us in politics as well. The country should be ruled by religious ...
Read More →What change will you observe if you test
[question] Question. What change will you observe if you test soap with litmus paper (red and blue)? [/question] [solution] solution: Soap is alkaline in nature therefore turns red litmus blue and no effect on blue litmus. [/solution]...
Read More →There are 40 villages in a district where the government has made no provision for drinking water.
[question] Question. There are 40 villages in a district where the government has made no provision for drinking water. These villagers met and considered many methods of forcing the government to respond to their need. Which of these is not a democratic method? (a) Filing a case in the courts claiming that water is part of right to life. (b) Boycotting the next elections to give a message to all parties. (c) Organising public meetings against government’s policies. (d) Paying money to governmen...
Read More →Explain the formation of scum
[question] Question. Explain the formation of scum when hard water is treated with soap. [/question] [solution] solution: Hard water contains calcium and magnesium ions. When soap comes in contact with hard water, these ions form calcium and magnesium salts of fatty acids which are insoluble in water. These calcium or magnesium salts precipitate out in the form of scum. [/solution]...
Read More →Summarize the rules for writing of distribution
[question] Question. Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements. [/question] [solution] Solution: The rules for writing of the distribution of electrons in various shells for the first eighteen elements are given below. (i) The maximum number of electrons that a shell can accommodate is given by the formula $' 2 n^{2}$ ', where ' $n$ ' is the orbit number or energy level index $(n=1,2,3 \ldots)$ The maximum number of electrons p...
Read More →