{"id":16641,"date":"2018-08-24T11:01:50","date_gmt":"2018-08-24T11:01:50","guid":{"rendered":"https:\/\/www.aplustopper.com\/?p=16641"},"modified":"2020-12-04T13:04:45","modified_gmt":"2020-12-04T07:34:45","slug":"selina-icse-solutions-class-9-chemistry-study-first-element-hydrogen","status":"publish","type":"post","link":"https:\/\/www.aplustopper.com\/selina-icse-solutions-class-9-chemistry-study-first-element-hydrogen\/","title":{"rendered":"Selina Concise Chemistry Class 9 ICSE Solutions Study of the First Element – hydrogen"},"content":{"rendered":"

Selina Concise Chemistry Class 9 ICSE Solutions Study of the First Element – hydrogen<\/span><\/h2>\n

ICSE Solutions<\/a>Selina ICSE Solutions<\/a><\/p>\n

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 9 Chemistry Chapter 7 Study of Gas Laws. You can download the Selina Concise Chemistry ICSE Solutions for Class 9 with Free PDF download option. Selina Publishers Concise Chemistry for Class 9 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.<\/p>\n

Download Formulae Handbook For ICSE Class 9 and 10<\/a><\/p>\n

Selina ICSE Solutions for Class 9 Chemistry Chapter 9 Study of the First Element – hydrogen<\/strong><\/p>\n

Exercise 9<\/strong><\/span><\/p>\n

Solution 1.<\/strong><\/span><\/p>\n

(a) The position of hydrogen in the periodic table<\/a>
\n<\/b>\"Selina
\nHydrogen is first element in the periodic table. It has an atomic number\u00a0l<\/strong>\u00a0and an atomic mass of 1.00794\u00a0amu<\/strong>, occupying\u00a0group – IA<\/strong>. Its position is peculiar because it is grouped with metals although it is a non-metal\u00a0properties. Hydrogen relate to\u00a0Group IA<\/strong>\u00a0as well as\u00a0Group VII A<\/strong>.<\/p>\n

(b)<\/strong>\u00a0The properties of hydrogen resemble the properties of Group IA elements (Alkali metals), and some of it resembles the properties of Halogens (VIIA), so Hydrogen was put at the top of the periodic table so that the symmetry of the modern periodic table is not disturbed.<\/p>\n

    \n
  1. All elements in Group- IA have one electron in outermost shell, so they havevalency\u00a0one.<\/li>\n
  2. These elements in Group-IA are good reducing agents.<\/li>\n
  3. All elements of this group formsoxide which are\u00a0highly basic and dissolves in water to form strong alkalis.<\/li>\n
  4. They impartcolour\u00a0to a flame.<\/li>\n<\/ol>\n

    Solution 2.<\/strong><\/span><\/p>\n

    Similarity of hydrogen with alkali metals and halogens<\/b><\/p>\n\n\n\n\n\n\n\n\n\n
    <\/td>\nSimilarity of hydrogen with alkali metals [Group 1 (IA)]<\/strong><\/td>\nSimilarity of hydrogen with halogens [Group 17 (VIIA)]<\/strong><\/td>\n<\/tr>\n
    Electronic configuration<\/strong><\/td>\nElectronic configuration = 1. Thus, 1electro in the outermost valence shell.<\/p>\n

    Example:
    \nH=1<\/strong>;\u00a0Li=2,\u00a01<\/strong>;\u00a0Na=2,8,1<\/strong>; K=2,8,8,1<\/strong><\/td>\n

    		\n

    One electron less than the nearest noble gas.<\/p>\n

    Example:
    \nH= 1 (He=2)
    \nF= 2,7 (Ne=2,8)
    \nCl= 2,8,7 (Ar=2,8,8)<\/p>\n<\/td>\n<\/tr>\n

    Ion formation<\/strong><\/td>\nElectropositive character exhibited.<\/p>\n

    H 1e–<\/sup> \u2192 H1+
    \n<\/sup>Li 1e–<\/sup>\u00a0\u2192 Li1+
    \n<\/sup>Na 1e–<\/sup>\u00a0\u2192 Na1+<\/sup><\/td>\n

    		Electronegative character exhibited.<\/p>\n

    H + 1e–<\/sup>\u00a0\u2192 H1-
    \n<\/sup>F + 1e–<\/sup>\u00a0\u2192 F1-
    \n<\/sup>Cl\u00a0+ 1e–<\/sup>\u00a0\u2192 Cl1-<\/sup><\/td>\n<\/tr>\n

    Valency<\/strong><\/td>\nElectrovalency\u00a0of one exhibited.<\/p>\n

    H1+<\/sup>\u00a0,\u00a0Li1+\u00a0<\/sup>, Na1+<\/sup><\/td>\n

    		\n

    Electrovalency\u00a0and\u00a0covalencyexhibited.<\/p>\n

    Hydrogen<\/strong>:<\/p>\n

    forms\u00a0NaH\u00a0(electrovalent)forms CH4<\/sub>(covalent)<\/p>\n

    Chlorine<\/strong>:<\/p>\n

    forms\u00a0NaCl\u00a0(electrovalent)
    \nforms CCl4<\/sub>\u00a0(covalent)<\/p>\n<\/td>\n<\/tr>\n

    Reactions<\/strong><\/td>\nStrong affinity for non-metals (example: O, S,\u00a0Cl)<\/p>\n

    Hydrogen<\/strong>: forms H2<\/sub>O; H2<\/sub>S;\u00a0HCl<\/p>\n

    Sodium<\/strong>: forms Na2<\/sub>O; Na2<\/sub>S;\u00a0NaCl<\/td>\n

    		__<\/td>\n<\/tr>\n
    Reducing agent<\/strong><\/td>\nActs as a reducing agent.<\/p>\n

    Hydrogen<\/strong>:<\/p>\n

    CuO\u00a0+\u00a0H2<\/sub>\u00a0\u2192 Cu\u00a0+\u00a0H2<\/sub>O<\/p>\n

    Sodium<\/strong>:<\/p>\n

    CuO\u00a0+\u00a02Na \u2192\u00a0Cu\u00a0+\u00a0Na2<\/sub>O<\/td>\n

    		__<\/td>\n<\/tr>\n
    Atomicity<\/strong><\/td>\n__<\/td>\n\n

    Diatomic molecules are formed. (Two atoms linked by a single bond)<\/p>\n

    Hydrogen
    \n<\/strong>H:H or H-H \u2192\u00a0H2<\/sub>\u00a0\"\"<\/p>\n

    Chlorine
    \n<\/strong>Cl:Cl\u00a0or\u00a0Cl-Cl \u2192\u00a0Cl2<\/sub>\"\"<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Resemblance with Halogens:<\/u><\/p>\n

      \n
    1. Both exist in the form of diatomic molecules.<\/li>\n
    2. Both show gaseous nature.<\/li>\n
    3. Both have a valency of 1.<\/li>\n
    4. Both are non-metals.<\/li>\n
    5. Both lose electron to term anions.<\/li>\n<\/ol>\n

      Solution 3.<\/strong><\/span><\/p>\n

      (a) Hydrogen is found in minute traces in the Earth’s crust and the Earth’s atmosphere. The atmosphere around the sun and stars is found to contain 1.1 % hydrogen.<\/p>\n

      (b) Henry Cavendish when prepared this gas from iron and dil. acids, he established its elementary nature and showed that when the gas burns in air, water is formed. It was on account of this property that Lavoisier in 1783 named it hydrogen (Greek word meaning water-former).<\/p>\n

      Solution 4.<\/strong><\/span><\/p>\n

      (a)\u00a0A\u00a0monovalent<\/span>\u00a0metal
      \n2Na\u00a0+\u00a0H2<\/sub>\u00a0\u2192 2NaH
      \n(Sodium hydride)<\/p>\n

      (b)\u00a0A divalent metal
      \nCa\u00a0+\u00a0H2<\/sub>\u00a0\u2192 CaH2
      \n<\/sub>(Calcium hydride)<\/p>\n

      Solution 5.<\/strong><\/span><\/p>\n

      (a) Calcium:<\/strong>\u00a0is not used in lab preparation of hydrogen because:<\/p>\n

        \n
      1. The reaction and very violent and exothermic hence dangerous.<\/li>\n
      2. The heat liberated ignites the hydrogen.<\/li>\n
      3. Calcium is expensive.<\/li>\n<\/ol>\n

        (b) Iron:<\/strong>\u00a0Iron reacts slowly at ordinary temperatures, hence requires heating. The hydrogen produced also contain impurities like\u00a0sulphur\u00a0dioxide and hydrogen\u00a0sulphide. Hence, it is not used in lab preparation of hydrogen.<\/p>\n

        (c)\u00a0Aluminium:<\/strong>\u00a0It is not used in the lab preparation of hydrogen because oxides of this metal keep sticking to the surface of the metal. Thus the steam does not come in contact with metal and hence reaction stops.\u00a0.<\/p>\n

        (d) Sodium:<\/strong>\u00a0It is riot used in the lab preparation of hydrogen because the reaction is violent. The sodium melts into a globule and darts about freely on the surface of water hence the collection of hydrogen is difficult.<\/p>\n

        Solution 6.<\/strong><\/span><\/p>\n

        Depending upon the nature of reaction taking place between metals and substances like air, water and acids, metals are arranged in a vertical series in order of their activity. Such a series is called activity series of metals.<\/p>\n

        The metals places near the\u00a0top<\/strong>\u00a0of the series are the\u00a0most reactive<\/strong>, while those placed near the\u00a0bottom<\/strong>\u00a0are the\u00a0least reactive<\/strong>.<\/p>\n

        When dilute hydrochloric acid or dilute\u00a0sulphuric\u00a0acid react with the metals above hydrogen in the activity series, they produce hydrogen. But the metals below hydrogen in the activity series do not.<\/p>\n

        Solution 7.<\/strong><\/span><\/p>\n

        (a)\u00a0Reactants:<\/strong>\u00a0Nitrogen and hydrogen\u00a0(Haber process)<\/strong><\/p>\n

        Chemical equation:
        \n\"Selina
        \n<\/strong><\/p>\n

        Observation and conditions
        \n<\/strong>Three volumes of hydrogen and one volume of nitrogen react at temperature 450o<\/sup>C-500o<\/sup>C at the pressure of 200-900\u00a0atm, in presence of a finely divided iron which acts as a catalyst, and promoter molybdenum.<\/p>\n

        (b)\u00a0Reactants:<\/strong>\u00a0Chlorine and hydrogen<\/p>\n

        Chemical equation:<\/strong>
        \n\"Selina<\/p>\n

        Observation and conditions
        \n<\/strong>Hydrogen and chlorine (in their equal volumes) react slowly in diffused sunlight but reacts explosively in direct sunlight. A spontaneous reaction takes place with the release of a large amount of energy.<\/p>\n

        (c)\u00a0Reactants:<\/strong>\u00a0Sulphur\u00a0and hydrogen<\/p>\n

        Chemical equation:
        \n<\/strong>H2<\/sub>\u00a0+ S \u2192\u00a0H2<\/sub>S
        \n<\/strong><\/p>\n

        Observation and conditions
        \n<\/strong>Hydrogen gas when passed through molten\u00a0sulphur, it reacts to give another gas, hydrogen\u00a0sulphide.<\/p>\n

        (d)\u00a0Reactants:<\/strong>\u00a0Oxygen and hydrogen<\/p>\n

        Chemical equation:
        \n<\/strong>2H2<\/sub>\u00a0+ O2<\/sub>\u00a0\u2192 2H2<\/sub>O
        \n<\/strong><\/p>\n

        Observation and conditions
        \n<\/strong>Hydrogen burns with a\u00a0pop sound<\/strong>\u00a0in oxygen. It burns with a pale blue flame forming water.<\/p>\n

        Solution 8.<\/strong><\/span><\/p>\n

        (a)\u00a0<\/strong>Among the given metals Zinc is most suitable.
        \n(i) Copper: In case of copper, It is placed below hydrogen in the activity series. So it does not displace hydrogen from acid.
        \nCu +\u00a0HCl \u2192\u00a0No reaction
        \n(ii) In case of Mg; it is a very expensive metal.
        \n(iii) In case of sodium, it reacts with explosively and violently.<\/p>\n

        (b)\u00a0<\/strong>Among the given acids we prefer dilute\u00a0sulphuric\u00a0acid.
        \nWe reject concentrated\u00a0sulphuric, dilute nitric and concentrated nitric acid because these are powerful\u00a0oxidising\u00a0agents and oxygen formed due to its decomposition\u00a0oxidises\u00a0the hydrogen to water.<\/p>\n

        (c)\u00a0<\/strong>Modification: Collect the gas by downward displacement of water when all the air from the apparatus has been expelled. Drying Agent used is Calcium Chloride.<\/p>\n

        Solution 9.<\/strong><\/span><\/p>\n

        (a)\u00a0Iron reacts reversibly with steam. Hence the hydrogen formed is removed as it is released to prevent reduction of\u00a0triferric<\/span>\u00a0tetraoxide<\/span>.
        \nFe\u00a0+\u00a04H2<\/sub>O \u2192\u00a0Fe3<\/sub>O4<\/sub>\u00a0+\u00a04H2<\/sub>\u00a0?
        \n(Steam)<\/p>\n

        (b)
        \n\"Selina<\/p>\n

        Solution 10.<\/strong><\/span><\/p>\n

        (a)\u00a0The metal is magnesium
        \n(b)\u00a0Mg\u00a0+\u00a0H2<\/sub>O \u2192\u00a0MgO\u00a0+\u00a0H2<\/sub><\/p>\n

        Solution 11.<\/strong><\/span><\/p>\n

        (a)<\/strong>\u00a0Substance A is\u00a0CuO\u00a0and substance B is Cu.<\/p>\n

        (b)<\/strong>\u00a0Test for water
        \n<\/u>(i) It is neutral to litmus
        \n(ii) It changes anhydrous copper\u00a0sulphate\u00a0into blue salt.<\/p>\n

        (c)<\/strong>\u00a0When substance\u00a0A\u00a0i.e,\u00a0CuO\u00a0reacts with hydrogen, it removes oxygen and we get free metal i.e. Cu.<\/p>\n

        (d)<\/strong>\u00a0CuO\u00a0+\u00a0H2<\/sub>\u00a0\u2192 Cu\u00a0+\u00a0H2<\/sub>O<\/p>\n

        (e)<\/strong>\u00a0No, there is no reaction between substance B and dilute hydrochloric acid because copper does not displace hydrogen from acids.<\/p>\n

        (f)<\/strong>\u00a0Cu +\u00a0HCl \u2192\u00a0No reaction<\/p>\n

        Solution 12.<\/strong><\/span><\/p>\n

        Magnesium lies above Hydrogen in reactivity series and can displace hydrogen from acid whereas, Mercury and silver lie below hydrogen in reactivity series and cannot displace hydrogen from acid and hence nothing happens.<\/p>\n

        Solution 13.<\/strong><\/span><\/p>\n

        Soap bubbles containing hydrogen rapidly rise up in air as hydrogen is lighter than air.<\/p>\n

        Solution 14.<\/strong><\/span><\/p>\n

        Bosch Process
        \n<\/u><\/strong>Bosch process consists of following steps.<\/p>\n

        Step 1 :<\/strong><\/p>\n

        Steam is passed over a hot coke (at 1000o<\/sup>C) in a special type\u00a0of a furnaces\u00a0called converters.
        \nIn this step carbon reacts with water to form carbon monoxide and hydrogen gas. This mixture is called water gas.\"Selina<\/p>\n

        Step 2 :<\/strong><\/p>\n

        In this step excess of steam is mixed with water gas and entire mixture is passed over heated ferric oxide and chromic oxide. Ferric oxide acts as catalyst and chromic oxide as promoter.
        \n\"Selina<\/p>\n

        Step 3 :<\/strong><\/p>\n

        In this step removal of carbon dioxide from reaction mixture takes place. The mixture of carbon dioxide and hydrogen is forced through cold water under pressure\u00a0at 30 atmospheric pressure\u00a0or through caustic potash solution which dissolve carbon dioxide leaving behind hydrogen gas.
        \n2KOH\u00a0+\u00a0CO2<\/sub>\u00a0\u2192 K2<\/sub>CO3<\/sub>\u00a0+\u00a0H2<\/sub>O<\/p>\n

        Step 4 :<\/strong><\/p>\n

        In this last step, mixture is passed through\u00a0ammonical\u00a0solution of cuprous chloride solution so as to dissolve carbon monoxide. CO is removed by\u00a0bubbling\u00a0the gas through\u00a0ammoniacal\u00a0cuprous chloride solution. The moisture is removed by cooling the gas about 20\u00b0C when water\u00a0vapoursfreeze. The pure and dry hydrogen gas is collected in steel cylinders.
        \nCuCl<\/span>\u00a0+\u00a0CO\u00a0+\u00a02H2<\/sub>O \u2192\u00a0CuCl.CO.2H2<\/sub>O<\/p>\n

        Solution 15.<\/strong><\/span><\/p>\n

        (a) Cold water:<\/strong><\/p>\n

        Sodium metal wrapped in small piece of wire gauze or Sodium amalgamated with mercury is used. This prevents sodium from darting about.
        \n2Na\u00a0+\u00a02H2<\/sub>O \u2192\u00a02NaOH\u00a0+\u00a0H2<\/sub>\u00a0\u2191<\/p>\n

        (b) Hot water:<\/strong><\/p>\n

        Zn or Mg can be used.
        \nMg\u00a0+\u00a0H2<\/sub>O \u2192\u00a0MgO\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(boiling water)<\/p>\n

        (C) Steam:<\/strong><\/p>\n

        Iron reacts with the steam and the reaction is reversible.\u00a0Iron reacts with steam when it is red hot as hydrogen is blown out of contact with iron by the force of current of the steam.
        \n\"Selina<\/p>\n

        Solution 16.<\/strong><\/span><\/p>\n

        Metals<\/u><\/strong><\/p>\n

        Mg, Al, Zn, Fe do not react with cold water. It reacts with boiling water liberating hydrogen gas but the reaction is very slow.
        \nMg, Al, Zn, Fe react with the hot steam in the heated state and form the corresponding oxide and hydrogen gas.
        \nIron reacts with the steam and the reaction is reversible.<\/p>\n

        Magnesium
        \n<\/strong>Reaction of boiling water with steam is slow but Mg liberates Hydrogen rapidly with steam.<\/p>\n

        Mg\u00a0+\u00a0H2<\/sub>O \u2192\u00a0MgO\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(boiling water)<\/p>\n

        Aluminium<\/strong><\/p>\n

        Gets coated with Al2<\/sub>O3<\/sub>\u00a0on rubbing with sand paper its oxide coating is removed and then it reacts with steam to produce hydrogen.<\/p>\n

        2Al\u00a0+\u00a0H2<\/sub>O \u2192\u00a0Al2<\/sub>O3<\/sub>\u00a0+\u00a03H2<\/sub>\u00a0\u2191
        \n(steam)<\/p>\n

        Zinc<\/strong><\/p>\n

        Zinc reacts with steam and produce zinc oxide and H2
        \n<\/sub><\/p>\n

        Zn +\u00a0H2<\/sub>O \u2192\u00a0ZnO\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(steam)<\/p>\n

        Iron<\/strong><\/p>\n

        Iron produces H2<\/sub>\u00a0when red hot the reaction is reversible but as soon as hydrogen is produced it is blown out of contact with iron by the force of the current of steam.<\/p>\n

        \"Selina
        \n(steam)<\/p>\n

        Non-metals<\/u><\/strong><\/p>\n

        Bosch Process (From Coke)
        \n<\/strong>Bosch process consists of following steps.<\/p>\n

        Step 1 :<\/strong><\/p>\n

        Steam is passed over a hot coke (at 1000o<\/sup>C) in a special type\u00a0of a furnaces\u00a0called converters.
        \nIn this step carbon reacts with water to form carbon monoxide and hydrogen gas. This mixture is called water gas.\"Selina<\/p>\n

        Step 2 :<\/strong><\/p>\n

        In this step excess of steam is mixed with water gas and entire mixture is passed over heated ferric oxide and chromic oxide. Ferric oxide acts as catalyst and chromic oxide as promoter.
        \n\"Selina<\/p>\n

        Step 3 :<\/strong><\/p>\n

        In this step removal of carbon dioxide from reaction mixture takes place. The mixture of carbon dioxide and hydrogen is forced through cold water under pressure\u00a0at 30 atmospheric pressure\u00a0or through caustic potash solution which dissolve carbon dioxide leaving behind hydrogen gas.<\/p>\n

        2KOH\u00a0+\u00a0CO2<\/sub>\u00a0\u2192 K2<\/sub>CO3<\/sub>\u00a0+\u00a0H2<\/sub>O<\/p>\n

        Step 4 :<\/strong><\/p>\n

        In this last step, mixture is passed through\u00a0ammonical\u00a0solution of cuprous chloride solution so as to dissolve carbon monoxide. CO is removed by\u00a0bubbling\u00a0the gas through\u00a0ammoniacal\u00a0cuprous chloride solution. The moisture is removed by cooling the gas about 20C when water\u00a0vapoursfreeze. The pure and dry hydrogen gas is collected in steel cylinders.<\/p>\n

        CuCl<\/span>\u00a0+\u00a0CO\u00a0+\u00a02H2<\/sub>O \u2192\u00a0CuCl.CO.2H2<\/sub>O<\/p>\n

        Solution 17.<\/strong><\/span><\/p>\n

        (a)\u00a0<\/strong>Zinc and iron lie above hydrogen in reactivity series and can displace hydrogen from acid.<\/p>\n

        Zn +\u00a0H2<\/sub>SO4<\/sub>\u00a0\u2192 ZnSO4<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(dilute)<\/p>\n

        Fe\u00a0+\u00a0H2<\/sub>SO4<\/sub>\u00a0\u2192 FeSO4<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(dilute)<\/p>\n

        (b)\u00a0<\/strong>Zn\u00a0+\u00a02HCl \u2192\u00a0ZnCl2<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(dilute)<\/p>\n

        Fe\u00a0+\u00a02HCl \u2192\u00a0FeCl2<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(dilute)<\/p>\n

        Copper lies below hydrogen. Thus, it cannot displace hydrogen from acids.<\/p>\n

        Solution 18.<\/strong><\/span><\/p>\n

        Two alkalis which can displace hydrogen are\u00a0NaOH\u00a0and KOH.<\/p>\n

        Aluminium<\/u><\/strong><\/p>\n

        2Al\u00a0+\u00a06NaOH \u2192\u00a02Na3<\/sub>AlO3<\/sub>\u00a0+ 3 H2<\/sub>\u00a0\u2191
        \n(Sodium\u00a0aluminate)<\/p>\n

        2Al\u00a0+\u00a02KOH\u00a0+\u00a02H2<\/sub>O \u2192\u00a02KAlO2<\/sub>\u00a0+ 3 H2<\/sub>\u00a0\u2191
        \n(Potassium meta\u00a0aluminate)<\/p>\n

        Zinc<\/u><\/strong><\/p>\n

        Zn\u00a0+\u00a02NaOH \u2192\u00a0Na2<\/sub>ZnO2<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(Sodium\u00a0zincate)<\/p>\n

        Zn +\u00a02KOH \u2192\u00a0K2<\/sub>ZnO2<\/sub>\u00a0+\u00a0H2<\/sub>\u00a0\u2191
        \n(Potassium\u00a0zincate)<\/p>\n

        Aluminium\u00a0and Zinc have unique nature; They react with acids and can even react with hot concentrated alkalis to form hydrogen and a soluble salt. Salt s (oxides and hydroxide) of these metals are\u00a0Amphoteric.<\/p>\n

        Question 19.
        \nComplete and balance the following reactions.
        \n(a) Na + H2O \u2192_____________ +___________
        \n(b) Ca + H2O \u2192_____________ +___________
        \n(c) Mg + H2O \u2192_____________ +___________
        \n(d) Zn + H2O \u2192_____________ +___________
        \n(c) Fe + H2O \u2192_____________ +___________
        \n(d) Zn + HCl \u2192_____________ +___________
        \n(e) Al + H2SO4 \u2192_____________ +___________
        \n(f) Fe + HCl \u2192_____________ +___________
        \n(g) Zn + NaOH \u2192_____________ +___________
        \n(h) Al + KOH + H2O\u2192_____________ +___________<\/p>\n

        Solution:<\/span><\/p>\n

        (a)\u00a02<\/strong>Na\u00a0+\u00a02<\/strong>H2<\/sub>O \u2192\u00a02NaOH\u00a0+\u00a0H2
        \n<\/sub>(b)\u00a0Ca\u00a0+\u00a02<\/strong>H2<\/sub>O \u2192\u00a0Ca(OH)2\u00a0<\/sub>+\u00a0H2
        \n<\/sub>(c)\u00a0Mg\u00a0+\u00a0H2<\/sub>O \u2192\u00a0MgO\u00a0+\u00a0H2
        \n<\/sub>(d)\u00a0Zn\u00a0+\u00a0H2<\/sub>O \u2192\u00a0ZnO\u00a0+\u00a0H2
        \n<\/sub>(e)\u00a03<\/strong>Fe\u00a0+\u00a04<\/strong>H2<\/sub>O \u2192\u00a0Fe3<\/sub>O4<\/sub>\u00a0+\u00a04H2
        \n<\/sub>(f)\u00a0Zn\u00a0+\u00a02<\/strong>HCl \u2192\u00a0ZnCl2<\/sub>\u00a0+\u00a0H2
        \n<\/sub>(g)\u00a02<\/strong>Al\u00a0+\u00a03<\/strong>H2<\/sub>SO4\u00a0<\/sub>\u00a0\u2192 Al2<\/sub>(SO4<\/sub>)3<\/sub>\u00a0+\u00a03H2
        \n<\/sub>(h)\u00a0Fe\u00a0+\u00a02<\/strong>HCl \u2192\u00a0FeCl2<\/sub>\u00a0+\u00a0H2
        \n<\/sub>(i)\u00a0Zn\u00a0+\u00a02<\/strong>NaOH \u2192\u00a0Na2<\/sub>ZnO2<\/sub>\u00a0+\u00a0H2
        \n<\/sub>(j)\u00a02<\/strong>Al\u00a0+\u00a02<\/strong>KOH\u00a0+\u00a02<\/strong>H2<\/sub>O \u2192\u00a02KAlO2<\/sub>\u00a0+\u00a03H2<\/sub><\/p>\n

        Solution 20.<\/strong><\/span><\/p>\n

        (a) Lead reacts with dilute sulphuric acid and hydrochloric acid and forms an insoluble coating of lead sulphate and lead chloride respectively. Hence, further reaction is prevented.<\/p>\n

        (b) When potassium and sodium react with dilute sulphuric acid, H2SO4 or dilute HCl, the reaction is highly explosive and practically not feasible.<\/p>\n

        Solution 21.<\/strong><\/span><\/p>\n

        (a) Sodium hydroxide + zinc\u00a0\u2192 hydrogen +\u00a0Sodium\u00a0zincate
        \n(b) Calcium + water\u00a0calcium \u2192 hydroxide +\u00a0Hydrogen<\/p>\n

        Solution 22.<\/strong><\/span><\/p>\n

          \n
        1. Hydrogen gas is collected by the downward displacement of water. This is because-\n