CBSE ADDA

1. Q. The description of atomic particles of two elements X and Y is given below Protons neutrons electrons X 8 8 8 Y 8 9 8 (i) What is the atomic number of Y? (ii) What is the mass number of X? (iii) What is the relation between X and Y? (iv) Which element/elements do they represent? (v) Write the electronic configuration of X? (vi) Write the cation/anion formed by the element Ans: (i) Atomic number of y =  8             (ii) Mass number of x – 16           (iii) x and y are isotopes   (iv) x and y represent – oxygen               (v) 2, 6                                       (vi) It will form an anion – O -2 2. Q. Which of the following are isotopes and which are isobars? Argon,  Protium, Calcium, Deuterium. Explain why the isotopes have similar chemical properties but they differ in physical properties? Ans: Isotopes – Protiu

CBSE NCERT Questions with solutions Q. State the role of the atmosphere in climate control? Ans: Atmosphere prevents sudden increase in temperature during the day light hours. It slows down the escape of heat into outer space during the night. Q. How is acid rain caused ? Ans: The fossil fuels like coal and petroleum/contain small amounts of nitrogen and sulphur/When the fossil fuels are burnt,/nitrogen and sulphur are burnt/and produces different oxides of nitrogen and sulphur/When these oxides dissolve in rain it gives rise to acid rain. Q. What are the different ways in which water gets polluted ? How does it affect the life forms ? Ans: (a) The addition of undesirable substances like fertilizers and pesticides, mercury salts in water/can cause cholera produced by the bacteria. (b) The removable of desired substances like oxygen from the water/adversely affect the aquatic organisms. (c) A sudden change in temperature in water bodies/would be dangerous and effect the

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