How does the electronic configuration of an atom relate
[question] Question. How does the electronic configuration of an atom relate to its position in the Modern Periodic Table? [/question] [solution] solution: In the Modern Periodic Table, atoms with similar electronic configurations are placed in the same group. In a group, the number of valence electrons remains the same. Elements across a period show an increase in the number of valence electrons in the same shell. [/solution]...
Read More →Fill in the gaps in the following table illustrating
[question] Question. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells. [/question] [solution] Solution: [/solution]...
Read More →Why is plasma membrane called
[question] Question. Why is plasma membrane called selectively permeable membrane? [/question] [solution] Solution: Cell membrane is semipermeable membrane for water. It permits the entry of gases through diffusion. Ions, sugar, amino acids, etc. pass through the plasma membrane by an active process. Plasma membrane is impermeable to certain other materials. Therefore, it is selectively permeable. [/solution]...
Read More →Nitrogen (atomic number 7 ) and phosphorus (atomic number 15 ) belong to group
[question] Question. Nitrogen (atomic number 7 ) and phosphorus (atomic number 15 ) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why? Element K L M Nitrogen 2 5 Phosphorus 2 8 5 [/question] [solution] solution: Nitrogen is more electronegative than phosphorus. On moving down a group, the number of shell increases. Therefore, the valence electrons move away from the nucleus and the effective nuclea...
Read More →How do substances like
[question] Question. How do substances like $\mathrm{CO}_{2}$ and water move in and out of the cell ? [/question] [solution] Solution: $\mathrm{CO}_{2}$ moves into and out of the cell by diffusion while water does it through osmosis. [/solution]...
Read More →The cost of 2 kg of apples and 1 kg of grapes on a day was found to be ` 160.
[question] Question. The cost of 2 kg of apples and 1 kg of grapes on a day was found to be ` 160. After a month, the cost of 4 kg of apples and 2 kg of grapes is ` 300. Represent the situation algebraically and geometrically. [/question] [solution] Solution: Let the cost of 1 kg of apple be ` x and the cost of 1 kg of grapes be ` y So, $2 x+y=160$ $4 x+2 y=300 x$ and [/solution]...
Read More →Why is the cell called structural and functional unit of life?
[question] Question. Why is the cell called structural and functional unit of life? [/question] [solution] Solution: A living organism is made up of one or more cells. Therefore, cell is structural and functional unit of life. All life functions of an organism reside in its cells. As the different parts of human body perform different functions. Similarly division of labour is also seen within a single cell. In fact each such cell has got certain specific components within it known as cell organ...
Read More →The position of three elements
[question] Question. The position of three elements A, B and C in the Periodic Table are shown below ? (a) State whether A is a metal or non-metal. (b) State whether C is more reactive or less reactive than A. (c) Will C be larger or smaller in size than B ? (d) Which type of ion, cation or anion, will be formed by element A? [solution] solution: (a) A is a non-metal. (b) C is more reactive than A (c) C will be smaller in size than B (d) A will form an anion [/solution]...
Read More →Ramesh was not in class when this chapter was being taught.
[question] Question. Ramesh was not in class when this chapter was being taught. He came the next day and repeated what he had heard from his father. Can you tell Ramesh what is wrong with these statements? (a) Women always vote the way men tell them to. So what is the point of giving them the right to vote? (b) Party politics creates tension in society. Elections should be decided by consensus not by competition. (c) Only graduates should be allowed to stand as candidates for elections. [/quest...
Read More →An atom has electronic configuration 2, 8, 7.
[question] Question. An atom has electronic configuration 2, 8, 7. (a) What is the atomic number of this element? (b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.) $\mathrm{N}(7) \mathrm{F}(9) \mathrm{P}(15) \mathrm{Ar}(18)$ [/question] [solution] solution: (a) The atomic number of this element is 17. (b) It would be chemically similar to F (9) with configuration as 2, 7. [/solution]...
Read More →Who discovered cell and how ?
[question] Question. Who discovered cell and how ? [/question] [solution] Solution: Robert Hooke (1665). The scientist found that cork possesses a number of small box-like structure which he named cell (cellula which later abbreviated to cell). His work was published in the form of a book called “Micrographia”. [/solution]...
Read More →Here are some reports of malpractices in Indian elections.
[question] Question. Here are some reports of malpractices in Indian elections. Identify what the problem in each case is. What should be done to correct the situation? (a) Following the announcement of elections, the minister promised to provide financial aid to reopen the closed sugar mill. (b) Opposition parties alleged that their statements and campaign was not given due attention in Doordarshan and All India Radio. (c) An inquiry by the Election Commission showed that electoral rolls of a s...
Read More →The coach of a cricket team buys 3 bats and 6 balls for ` 3900.
[question] Question. The coach of a cricket team buys 3 bats and 6 balls for ` 3900. Later, she buys another bat and 3 more balls of the same kind for ` 1300. Represent this situation algebraically and geometrically [/question] [solution] Solution: Let the cost of 1 bat be ` x and the cost of 1 ball be ` y So, $3 x+6 y=3900$ and $x+3 y=1300$ and [/solution]...
Read More →Here are some reports of electoral malpractices from different parts of the world.
[question] Question. Here are some reports of electoral malpractices from different parts of the world. Is there anything that these countries can learn from India to improve their elections? What would you suggest in each case? (a) During an election in Nigeria, the officer in charge of counting votes deliberately increased the votes of one candidate and declared him elected. The court later found out that more than five lakh votes cast for one candidate were counted in favour of another. (b) J...
Read More →(a) What property do all elements in the same column of the Periodic Table as boron have in common?
[question] Question. (a) What property do all elements in the same column of the Periodic Table as boron have in common? (b) What property do all elements in the same column of the Periodic Table as fluorine have in common? [/question] [solution] solution: (a) All the elements in the same column as boron have the same number of valence electrons (3). Hence, they all have valency equal to 3. (b) All the elements in the same column as fluorine have the same number of valence electrons (7). Hence, ...
Read More →Chinappa was convicted for torturing his wife for dowry.
[question] Question. Chinappa was convicted for torturing his wife for dowry. Satbir was held guilty of practicing untouchability. The court did not allow either of them to contest elections. Does this decision go against the principles of democratic elections? [/question] [solution] Solution: This decision does not go against the principles of democratic elections as both Chinappa and Satbir are criminals, and hence, should be prevented from holding positions in the central or state assemblies....
Read More →Which element has
[question] Question. Which element has (a) two shells, both of which are completely filled with electrons? (b) the electronic configuration 2, 8, 2 ? (c) a total of three shells, with four electrons in its valence shell? (d) a total of two shells, with three electrons in its valence shell? (e) twice as many electrons in its second shell as in its first shell? [/question] [solution] solution: (a) Neon has two shells, both of which are completely filled with electrons (2 electrons in K shell and 8...
Read More →Can we draw the following conclusions from the information given in this chapter?
[question] Question. Can we draw the following conclusions from the information given in this chapter? Give two facts to support your position for each of these. (a) Election Commission of India does not have enough powers to conduct free and fair elections in the country. (b) There is a high level of popular participation in the elections in our country. (c) It is very easy for the party in power to win an election. (d) Many reforms are needed to make our elections completely free and fair [/qu...
Read More →Complete the following table.
[question] Question. [/question] [solution] Solution: [/solution]...
Read More →Aftab tells his daughter, "Seven years ago, I was seven times as old as you were then
[question] Question. Aftab tells his daughter, "Seven years ago, I was seven times as old as you were then. Also, three years from now, I shall be three times as old as you will be". (Isn't this interesting?) Represent this situation algebraically and graphically. [/question] [solution] Solution: Let the present age of Aftab's daughter = x years. and the present age of $A f t a b=y$ years $(yx)$ According to the given conditions Seven years ago, $(y-7)=7 \times(x-7)$ i.e., $\quad y-7=7 x-49$ i.e...
Read More →Surekha is an officer in-charge of ensuring free and fair elections in an assembly constituency in a state.
[question] Question. Surekha is an officer in-charge of ensuring free and fair elections in an assembly constituency in a state. Describe what should she focus on for each of the following stages of election: (a) Election campaign (b) Polling day (c) Counting day [/question] [solution] Solution: (a) Election campaign − For this, Surekha will have to focus on seeing that the candidates do not bribe or threaten the voters; appeal to them in the name of caste or religion; use government resources f...
Read More →Which one of the following is a correct
[question] Question. Which one of the following is a correct electronic configuration of sodium? (a) 2,8 (b) $8,2,1$ (c) $2,1,8$ (d) $2,8,1$ [/question] [solution] Solution: (d) [/solution]...
Read More →Match the following:
[question] Question. Match the following: [/question] [solution] Solution: [/solution]...
Read More →Choose the correct answer :
[question] Question. Choose the correct answer : Number of valence electrons in $\mathrm{Cl}^{-}$ion are (a) 16 (b) 8 (c) 17 (d) 18 [/question] [solution] Solution: (b) [/solution]...
Read More →Which of the following statements about the reasons for conducting elections are false?
[question] Question. Which of the following statements about the reasons for conducting elections are false? (a) Elections enable people to judge the performance of the government. (b) People select the representative of their choice in an election. (c) Elections enable people to evaluate the performance of the judiciary. (d) People can indicate which policies they prefer. [/question] [solution] Solution: Statement ‘c’ is false. [/solution]...
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