CBSE ADDA

CBSE ADDA Chapter 1, Chemical Reactions and Equations NCERT Science Textbook In-Text Questions (Answers) (Page 6) Q.1: Why should magnesium ribbon be cleaned before burning in air ? Ans: Magnesium ribbon is a very reactive metal. When stored it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide being a stable compound prevents further reaction of magnesium with oxygen. The magnesium is cleaned before burning in air to remove this layer so that the metal can be exposed to air properly. Q.2: Write the balanced equation for the following chemical reactions: (i) Hydrogen + Chlorine --> Hydrogen chloride (ii) Sodium + Water --> Sodium hydroxide + Hydrogen Ans: (i) H2 (g) + Cl2 (g) --> 2HCl (g) (ii) 2Na (s) + 2H2O (liq) --> 2NaOH (aq) + H2 (g). Q.3: Write a balanced chemical equation with state symbols for the following chemical reactions: (i) Solution of barium chloride and sodium sulphate in water t

CBSE ADDA Chapter 1, Chemical Reactions and Equations Solutions of Science Textbook Exercise Questions Q.1: Which of the statements about the reaction below are incorrect? 2PbO + C ---> 2Pb + CO2­ (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidized. (c) Carbon is getting oxidized. (d) Lead oxide is getting reduced. (i) a and b (ii) a and c (iii) a, b and c (iv) all. Ans: (i) a and b. Q.2: Fe2O3 + 2Al ---> Al2O3 + 2Fe The above reaction is an example of a (a) combination reaction (b) double displacement reaction (c) decomposition reaction (d) displacement reaction. Ans: (d) Q.3: What happens when dilute HCl is added to iron filings ? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. Ans: (a) Q.4: What is a balanced chemical equation ? Why should chemical equation be balanced ?

JSUNILTUTORIAL PUNJABI COLONY GALI NO Multiple choice question  CHEMISTRY X   Chemical Reaction and Equations 1. Respiration is: (a) Endothermic reaction (b)Exothermic reaction (c) Addition reaction (d) None 2. Photolysis is: (a) Decomposition (b) Addition (c) Displacement (d) Oxidation 3. Fe2O3 + 3CO → 2Fe + 3CO2, which is reducing agent in the above reacton:  (a) Fe2O3 (b) CO (c) Fe (d) CO2 4. What are the conditions for rusting of an iron article: (a) Presence of air (b) Presence of moisture (c) Both (d) None 5. Plaster of Paris is (a) 2CaSO4.H2O (b) CaSO41/2H2O (c) Both (d) None 6. Oxidation reaction is a chemical process in which a substance: (a) Gains hydrogen (b) Gains oxygen (c) Gains chlorine (d) None  7. Hydration means: a) addition of hydrogen (b) addition of hydrogen chloride (c) addition of sulphuric acid (d) addition of water  8.The decomposition of CaCO3 is (a) an endothermic reactio

CBSE ADDA _ Quick recap  Chemicals Equations  1. Chemical reactions- Chemical changes or chemical reactions are the changes in which one or more new substances are formed. 2. Chemical Equations – Representation of a chemical reaction in terms of symbols and formulae of the reactants and products is known as chemical equation. 3. Balanced Chemical equation – The chemical equation in which the no. of atoms of different elements is same on both sides of the arrow is called balanced chemical equation. 4. The chemical reactions can be classified into different types such as (a) Combination reactions- The reactions in which two or more substances combine to form a new substance are called combination reactions. For example, 2Mg(s) + O2 (g) → 2 MgO (s) (b) Decomposition reactions – The reactions in which a single compound breaks up into two or more simpler substances are called decomposition reactions. For example, 2Pb (NO3)2 (s) → 2PbO(s) + 4NO2 (g) + O2 (g) The decompos

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1. Find the equation of the set of points which are equidistant from the points (1, 2, 3) and (3, 2, –1).   [Hint: let the point be P(x, y, z). given points be A(1, 2, 3) and B(3, 2, - 1). Then PA = PB] ans: x – 2z = 0 2.Find the equation of the set of points P, the sum of whose distances from A (4, 0, 0) and B (– 4, 0, 0) is equal to 10.  [Hint: let the point be P(x, y, z). given points be A(4, 0, 0) and B(-4, 0, 0). Then PA + PB = 10] 3.Find the coordinates of the point which divides the line segment joining the points (– 2, 3, 5) and (1, – 4, 6) in the ratio (i) 2 : 3 internally, (ii) 2 : 3 externally.  Ans: i) (-4/5, 1/5, 27/5) ii) (-8, 17, 3) 4.Given that P (3, 2, – 4), Q (5, 4, – 6) and R (9, 8, –10) are collinear. Find the ratio in which Q divides PR.  Ans : 1:2  5. Find the ratio in which the YZ-plane divides the line segment formed by joining the points (–2, 4, 7) and (3, –5, 8).  [hint: any point on YZ plane is of the form (0, y, z)] ans: 2:3  6. Find