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O] BYJ U's NCERT Solution for class 10 Science Chapter 3 Metals and Non-metals, , The Learning App, , In-text questions set 1, Page number 40, , 1. Give an example of a metal which, (i) Is a liquid at room temperature?, (ii) Can be easily cut with a knife?, (iii) Is the best conductor of heat?, (iv) Is a poor conductor of heat?, , Solution:, , (i) Mercury is the metal which is liquid at room temperature, (ii) Sodium and potassium are the metals which can be cut with a knife:, (iii) Silver is the best conductor of heat, , (iv) Mercury and lead are poor conductor of heat., 2. Explain the meanings of malleable and ductile., Solution:, , i. Metals which can be beaten to sheets are said to be malleable, ii. Metals which can be drawn into thin wires are said to be ductile, , In-text questions set 2, Page number 46, , 1. Why is sodium kept immersed in kerosene oil?, , Solution: Sodium is a reactive metals, if kept open it will react with oxygen to explore and, catch fire. Sodium metal is kept immersed in kerosene to prevent their reaction with oxygen,, moisture and carbon dioxide of air., , 2. Write equations for the reactions of
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(i) iron with steam, (ii) calcium and potassium with water, , Solution: (i) Iron reacts with steam to form a magnetic oxide of Fe with the liberation of H»., , 3Fe(s) + 4H20(g) + FesO,(s) + 4H2{g), (ii) Calcium reacts with water to form calcium hydroxide and hydrogen., , Ca(s) + 2H2O(1) > Ca(OH)2(aq) + Ha(g), , Potassium reacts with cold water violently immediately with evolution of H, which catches, fire., , 2K(s) + 2H2O(1) + 2KOH(aq) + 2Ha(g), , 3. Samples of four metals A, B, C and D were taken and added to the following, solution one by one. The results obtained have been tabulated as follows, , Metal Iron) | Copper) | Zine Silver Nitrate, sulphate sulphate sulphate, , , , , , Noreaction | Displacement | , , , Displacement | - , , , Noreaction |Noreaction | Noreaction | Displacement, , , , , , , , , , SO >, , Noreaction | No reaction Noreaction | No reaction, , , , , , , , , , , , , , Use the Table above to answer the following questions about metals A, B, C and D,, , (i) Which is the most reactive metal?, (ii) What would you observe if B is added to a solution of Copper (II), , sulphate?, (iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
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Solution:, , (i) Metal B is the most reactive as it gives displacement reaction with iron (1J) sulphate., , (ii) When metal B is added to copper (II) sulphate solution, a displacement reaction will take, place because of which the blue colour of copper (11) sulphate solution will fade and a redbrown deposit of copper will be formed on metal B., , (iii)Metal B is the most reactive because it displaces iron from its salt solution. Metal A is less, reactive because it displaces copper from its salt solution. Metal C is still Jess reactive because it, can displace only silver from its salt solution and metal D is the least reactive because it cannot, displace any metal from its salt solution. Hence, the decreasing order of reactivity of the metals, , isB>A>C>D., , 4. Which gas is produced when dilute hydrochloric acid is added to a reactive, metal? Write the chemical reaction when iron reacts with dilute H,SO4,, Solution: Hydrogen gas is liberated when dilute HCI is added to a reactive metal., , Fe(s) + H»SO,(aq) + FeSO,4(aq) + Ho(g), , 5- What would you observe when zinc is added to a solution of iron (II) sulphate?, , Write the chemical reaction that takes place., Solution: Zinc is more reactive (more electro positive) than iron. Therefore Zinc displaces, Iron from its salt solution. The colour of ferrous sulphate is pale green, which turns colourless., , FeSO, + Zn — ZnSO, + Fey), Light green Zinc sulphate(Colourless), , In-text questions set 3 Page number 49, , 1. (i) Write the electron-dot structures for sodium and oxygen., , Gi) Show the formation of NasO and MgO by the transfer of electrons., (iii)What are the ions present in these compounds?, , Solution: (i) Sodiam:
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(ii) Formation of Magnesium oxide;, When magnesium reacts with oxygen, the magnesium atom transfers its two outermost, electrons to an oxygen atom. By losing two electrons, the magnesium atoms form a magnesium, , jon (Mg2+) and by gaining two electrons, tle oxygen atom forms an oxide ion (O*),, , Mg: + . Ss MgO, , Formation of Sodium oxide:, , Two sodium atoms transfer their 2 outermost electrons to an oxygen atom. By losing two, electrons, the two sodium atoms form sodium ions (2Na*). And by gaining two electrons,, , the oxygen atom forms an oxide ion (O>)., , Na., + O: ———_» Na,0, Na., , (iii) The ions present in sodium oxide compound {Na2O) are sodium ions (2Na*) and oxide, , ions (O?).
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The ions present in Magnesium oxide compound (MgO) are magnesium ions Mg? and oxide, ions (O02)., , 2. Why do ionic compounds have high melting points?, , Solution: Ionic compounds are the ones which has both positive and negative charges. Hence, there will be strong force of attraction between them, This make expenditure of lot of heat to, break this force of attraction hence ionic compounds have high melting points., , In-text questions set 4, Page number 53, , 1. Define the following terms., , (i) Mineral, (it) Ore, , (iii) Gangue, Solution:, , (i) Minerals are compounds (also known as elements) which are found naturally in the, earth’s crust. E.g. Alums, K2SO4.Alo(SO4)3.24H20, ete., , (ii) Ores are minerals from which metal can be extracted Ex: Bauxite Al2O3.2H:0 is the ore, of Al, copper pyrite CuFeS2.All minerals are not considered as ores but all ores are also, minerals., , {iii) Ores mined from the earth are naturally contaminated with sand, rocky materials. There, are impurities present in the ore which are known as gangue., , 2. Name two metals which are found in nature in the free state, Solution: Gold and platinum are the two metals found in Free State in nature., , 3. What chemical process is used for obtaining a metal from its oxide?, Reduction method is used to obtain metal from its oxide. Ex: Zinc oxide is reduced to metallic, zinc hy Heating with carbon.
