{"id":7954,"date":"2023-05-26T17:05:41","date_gmt":"2023-05-26T11:35:41","guid":{"rendered":"https:\/\/apboardsolutions.in\/?p=7954"},"modified":"2023-05-27T17:25:59","modified_gmt":"2023-05-27T11:55:59","slug":"ap-board-9th-class-physical-science-solutions-chapter-6","status":"publish","type":"post","link":"https:\/\/apboardsolutions.in\/ap-board-9th-class-physical-science-solutions-chapter-6\/","title":{"rendered":"AP Board 9th Class Physical Science Solutions Chapter 6 Chemical Reactions and Equations"},"content":{"rendered":"

AP State Syllabus AP Board 9th Class Physical Science Solutions<\/a> Chapter 6 Chemical Reactions and Equations Textbook Questions and Answers.<\/p>\n

AP State Syllabus 9th Class Physical Science Solutions 6th Lesson Chemical Reactions and Equations<\/h2>\n

9th Class Physical Science 6th Lesson Chemical Reactions and Equations Textbook Questions and Answers<\/h3>\n

Improve Your Learning<\/span><\/p>\n

Question 1.
\nWhat is a balanced chemical equation? Why should chemical equations be balanced?
\nAnswer:
\n1) A chemical equation in which the number of atoms of different elements on the reactants side (left side) are same as those on product side (right side) is called a balanced chemical equation.
\nEx : Zn + 2HCl \u2192 ZnCl2<\/sub> + H2<\/sub> \u2191<\/p>\n

2) All the chemical equations must balance because atoms are neither created nor destroyed in chemical reactions.<\/p>\n

3) The number of atoms of each element before and after reaction must be the same.<\/p>\n

4) According to the law of conservation of mass, the total mass of the substances that are taking part in a chemical reaction must be the same before and after the reaction.<\/p>\n

Question 2.
\nBalance the following chemical equations.
\na) NaOH + H2<\/sub>SO4<\/sub> \u2192 Na2<\/sub>SO4<\/sub> + H2<\/sub>O
\nb) Hg (NO3<\/sub>)2<\/sub> + KI \u2192 Hgl2<\/sub> + KNO3<\/sub>
\nc) H2<\/sub> + O2<\/sub> \u2192 H2<\/sub>O
\nd) KClO3<\/sub> \u2192 KCl + O2<\/sub>
\ne) C3<\/sub>H8<\/sub> + O2<\/sub> \u2192 CO2<\/sub> + H2<\/sub>O
\nAnswer:
\na) 2NaOH + H2<\/sub>SO4<\/sub> \u2192 Na2<\/sub>SO4<\/sub> + 2H2<\/sub>O
\nb) Hg (NO3<\/sub>)2<\/sub> + 2 KI \u2192 Hgl2<\/sub> + 2KNO3<\/sub>
\nc) 2H2<\/sub> + O2<\/sub> \u2192 2H2<\/sub>O
\nd) 2KClO3<\/sub> \u2192 2KCl + 3O2<\/sub>
\ne) C3<\/sub>Hg + 5O2<\/sub> \u2192 3CO2<\/sub> + 4H2<\/sub>O<\/p>\n

\"AP<\/p>\n

Question 3.
\nWrite the balanced chemical equations for the following reactions.
\na) Zinc + Silver nitrate \u2192 Zinc nitrate + Silver
\nb) Aluminium + Copper chloride \u2192 Aluminium chloride + Copper
\nc) Hydrogen + Chlorine \u2192 Hydrogen chloride
\nd) Ammonium nitrate \u2192 Nitrous Oxide + Water
\nAnswer:
\na) Zn + 2AgNO3<\/sub> \u2192 Zn(NO3<\/sub>)2<\/sub> + 2Ag
\nb) 2Al + 3CuCl2<\/sub> \u2192 2AlCl3<\/sub> + 3Cu
\nc) H2<\/sub> + Cl2<\/sub> \u2192 2HCl
\nd) NH4<\/sub>NO3<\/sub> \u2192 N2<\/sub>O + 2H2<\/sub>O<\/p>\n

Question 4.
\nWrite the balanced chemical equations for the following and identify the type of reaction in each case.
\na) Calcium hydroxide(aq) + Nitric acid(aq) \u2192 Water(l) + Calcium nitrate(aq)
\nb) Magnesium(sJ + Iodine \u2192 Magnesium Iodide(s)
\nc) Magnesium(s) + Hydrochloric acid(aq) \u2192 Magnesium chloride(aq) + Hydrogen^
\nd) Zinc(s) + Calcium chloride(aq) \u2192 Zinc Chloride(aq) + Calcium(s)
\nAnswer:
\na) Ca(OH2<\/sub>) + HNO3<\/sub> \u2192 H2<\/sub>O + Ca(NO3<\/sub>)2<\/sub>
\nThis is double decomposition reaction.<\/p>\n

b) Mg + I2<\/sub> \u2192 Mgl2<\/sub>
\nThis is chemical combination reaction.<\/p>\n

c) Mg + 2HCl \u2192 MgCl2<\/sub> + H2<\/sub> \u2191
\nThis is chemical displacement reaction.<\/p>\n

d) Zn + CaCl2<\/sub> \u2192 ZnCl2<\/sub> + Ca
\nThis is chemical displacement reaction. This reaction is not possible, because calcium is more reactive than zinc.<\/p>\n

\"AP<\/p>\n

Question 5.
\nWrite an equation for decomposition reaction where energy is supplied in the form of heat \/ light \/ electricity.
\nAnswer:
\nChemical decomposition reaction : A chemical reaction in which a single substance splits into two or more substances is called chemical decomposition.
\nFor decomposition reaction energy is supplied in the form of :
\n\"AP<\/p>\n

Question 6.
\nWhat do you mean by precipitation reaction?
\nAnswer:
\nA reaction in which insoluble substance in water is formed as product is called precipitation reaction.<\/p>\n

Question 7.
\nHow does chemical displacement reactions differ from chemical decomposition reaction? Explain with an example for each.
\nAnswer:
\n\"AP<\/p>\n

Question 8.
\nName the reactions taking place in the presence of sunlight.
\nAnswer:
\n1) In the presence of sunlight plants prepare their food by taking C02 from the air and H20 from the soil with their chloroplasts of the green leaves. This reaction is called photosynthesis.
\n\"AP<\/p>\n

Question 9.
\nWhy does respiration considered as an exothermic reaction? Explain.
\nAnswer:<\/p>\n

    \n
  • We need energy to stay alive.<\/li>\n
  • We get this energy from food we eat.<\/li>\n
  • During digestion, food is broken down into simpler substances.<\/li>\n
  • For example, rice and potato contains starch.<\/li>\n
  • The starch breaks down to form glucose.<\/li>\n
  • This glucose combines with oxygen in the cells of our body and releases energy, which helps to do the various works.<\/li>\n
  • During this process, energy is given out. Hence this reaction can be called exothermic reaction.<\/li>\n
  • The special name of this reaction is respiration.<\/li>\n
  • So respiration is considered as exothermic reaction.<\/li>\n
  • C6<\/sub>H12<\/sub>O6<\/sub> + 6O2<\/sub> \u2192 6CO2<\/sub> + 6H2<\/sub>O + Q (Energy)<\/li>\n<\/ul>\n

    \"AP<\/p>\n

    Question 10.
    \nWhat is the difference between displacement and double displacement reactions? Write equations for these reactions.
    \nAnswer:<\/p>\n\n\n\n\n\n\n
    Chemical displacement reaction<\/td>\nChemical double displacement reaction<\/td>\n<\/tr>\n
    1. In a reaction when an active element displaces less active element from its compound is called displacement reaction.<\/td>\n1. If two reactants exchange their constituents chemically and form two products, then the reaction is called as double displacement reaction.<\/td>\n<\/tr>\n
    2. Zn + 2HCl \u2192 ZnCl2<\/sub> + H2
    \n<\/sub>In this example Zn displaces Hydrogen from HCl.<\/td>\n    		2. Na2<\/sub>SO4<\/sub> + BaCl2<\/sub> \u2192 BaSO4<\/sub> + 2NaCl
    \nIn this reaction SO4<\/sub>2-<\/sup> and Cl–<\/sup> are mutually exchanged.<\/td>\n<\/tr>\n
    3. General formula to the reaction is
    \nA + BC \u2192 AC + B<\/td>\n    		3. General formula to the reaction is
    \nAB + CD \u2192 AD + BC<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Question 11.
    \nMnOz + 4HCl \u2192 MnCl2<\/sub> + 2H2<\/sub>O + Cl2<\/sub> \u2191
    \nIn the above equation, name the compound which is oxidized and which is reduced.
    \nAnswer:
    \nIn the above equation, HCl compound is oxidized and MnO2<\/sub> is reduced.<\/p>\n

    Question 12.
    \nGive two examples for oxidation-reduction reaction.
    \nOxidation :
    \nOxidation is a reaction that involves the addition of oxygen or loss of hydrogen or electrons.
    \n\"AP<\/p>\n

    Reduction :
    \nThe process in which a substance loses oxygen or gains hydrogen or electrons is known as reduction.
    \n\"AP<\/p>\n

    Question 13.
    \nIn the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write the reaction involved.
    \nAnswer:<\/p>\n

      \n
    • Cu(s)<\/sub> + 2 AgNO3(aq)<\/sub> > Cu(NO3<\/sub>)2(aq)<\/sub> + 2Ag(s)<\/sub><\/li>\n
    • This is redox reaction, copper is the reducing agent and the silver is reduced.<\/li>\n
    • Electrons from the copper metal are transferred to the silver.<\/li>\n
    • This reaction can also be called a displacement reaction because copper displaces silver as it is more reactive.<\/li>\n<\/ul>\n

      Question 14.
      \nWhat do you mean by corrosion? How can you prevent it?
      \nAnswer:<\/p>\n

        \n
      • When some metals are exposed to moisture, acids, etc. they tarnish due to the formation of respective metal oxide on their surface. This process is called “corrosion”.<\/li>\n
      • Corrosion can be prevented by painting, oiling, greasing, galvanizing, chrome plating or making alloys.<\/li>\n
      • Galvanizing is a method of protecting iron from rusting by coating them a thin layer of zinc.<\/li>\n<\/ul>\n

        \"AP<\/p>\n

        Question 15.
        \nExplain rancidity.
        \nAnswer:<\/p>\n

          \n
        • Oxidation reactions in food material that were left for a long period are responsible for spoiling of food. This process is called “rancidity”.<\/li>\n
        • When these processes occur in food, undesirable odours and flavours can result.<\/li>\n
        • Rancidity is an oxidation reaction.<\/li>\n<\/ul>\n

          Question 16.
          \nBalance the following chemical equations including the physical states,
          \na) C6<\/sub>H12<\/sub>O6<\/sub> \u2192 C2<\/sub>H5<\/sub>OH + CO2<\/sub>
          \nb) Fe + O2<\/sub> \u2192 Fe2<\/sub>O3<\/sub>
          \nc) NH3<\/sub> + Cl2<\/sub> \u2192 N2<\/sub>H4<\/sub> + NH4<\/sub>Cl
          \nd) Na + H2<\/sub>O \u2192 NaOH + H2<\/sub>
          \nAnswer:
          \na) C6<\/sub>H12<\/sub>O6(s)<\/sub> \u2192 C2<\/sub>H5<\/sub>OH(l)<\/sub> + CO2(g)<\/sub>
          \nb) Fe(s)<\/sub> + O2(g)<\/sub> \u2192 Fe2<\/sub>O3(s)<\/sub>
          \nc) NH3(aq)<\/sub> + Cl2(g)<\/sub> \u2192 N2<\/sub>H4(l)<\/sub> + NH4<\/sub>Cl(aq)<\/sub>
          \nd) 2Na(s)<\/sub> + 2H2<\/sub>O(l)<\/sub> \u2192 NaOH + H2<\/sub><\/p>\n

          Question 17.
          \nBalance the chemical equation by including the physical states of the substances for the following reactions.
          \na) Barium chloride and Sodium sulphate aqueous solutions react to give insoluble Barium sulphate and aqueous solution of Sodium chloride.
          \nb) Sodium hydroxide reacts with Hydrochloric acid to produce Sodium chloride and water.
          \nc) Zinc pieces react with dilute Hydrochloric acid to liberate Hydrogen gas and forms Zinc chloride.
          \nAnswer:
          \na) BaCl2(aq)<\/sub> + Na2<\/sub>SO4(aq)<\/sub> \u2192 BaSO4(s)<\/sub>\u2193 + NaCl(aq)<\/sub>
          \nb) NaOH(aq)<\/sub> + HCl(aq)<\/sub> \u2192 NaCl(aq)<\/sub> + H2<\/sub>O(l)<\/sub>
          \nc) Zn(s)<\/sub> + 2HCl(aq)<\/sub> \u2192 ZnCl2(aq)<\/sub> + H2(g)<\/sub><\/p>\n

          \"AP<\/p>\n

          Question 18.
          \nA shiny brown coloured element \u2018X\u2019 on heating in air becomes black in colour. Can you predict the element \u2018X\u2019 and the black coloured substance formed? How do you support your predictions?
          \nAnswer:
          \nThe brown coloured element is copper (Cu). On heating copper reacts with oxygen
          \npresent in the atmosphere to form copper oxide which is black in colour.
          \nThe reaction is shown below.
          \n\"AP<\/p>\n

          If we pass hydrogen gas over hot copper oxide we will notice that black coating on copper turns brown because copper oxide loses oxygen to form copper.
          \nThis will support our prediction.
          \n\"AP<\/p>\n

          Question 19.
          \nWhy do we apply paint on iron articles?
          \nAnswer:<\/p>\n

            \n
          • Ferrous reacts with oxygen in the air and form iron oxide.
            \n2 Fe + O2<\/sub> \u2192 2 FeO<\/li>\n
          • This reaction is called corrosion. It spoils the iron articles by rusting.<\/li>\n
          • Corrosion of iron articles can be prevented or minimized by shielding the metal surface from oxygen and moisture.<\/li>\n
          • It can be prevented by applying paint on the articles.<\/li>\n<\/ul>\n

            Question 20.
            \nWhat is the use of keeping food in air tight containers?
            \nAnswer:<\/p>\n

              \n
            • Oxidation is defined as the interaction of oxygen molecules with all the different substances from metal to living tissue which may come into contact with it.<\/li>\n
            • When fats and oils are oxidized they become rancid. Their smell and taste change.<\/li>\n
            • Keeping food in airtight containers helps to slow down oxidation process.<\/li>\n
            • So, manufacturers of potato chips usually flush bags of chips with gas such as nitrogen to prevent the chips from getting oxidized.<\/li>\n<\/ul>\n

              Fill in the Blanks<\/span><\/p>\n

              1. The decomposition of vegetable into compost is an example of ……………. reaction.
              \n2. The chemical reaction in which energy is absorbed to form a new compound is called ………….
              \n3. The reaction 2N2<\/sub>O \u2192 2N2<\/sub> + O2<\/sub> is an example for ………….. reaction.
              \n4. The reaction Ca + 2H2<\/sub>O \u2192 Ca(OH)2<\/sub> + H2<\/sub> \u2191 is an example for ………….. reaction.
              \n5. The substances that are present on left side of a chemical equation are called
              \n6. The arrow mark between the products and reactants of a chemical equation shows of the reaction.
              \nAnswer:<\/p>\n

                \n
              1. oxidation<\/li>\n
              2. endothermic reaction<\/li>\n
              3. decomposition<\/li>\n
              4. displacement<\/li>\n
              5. reactants<\/li>\n
              6. direction<\/li>\n<\/ol>\n

                7. Match the following :<\/p>\n\n\n\n\n\n\n
                1) 2AgNO3<\/sub> + Na2<\/sub>CrO4<\/sub> \u2192 Ag2<\/sub>CrO4<\/sub> + 2NaNO3<\/sub><\/td>\na) combination reaction<\/td>\n<\/tr>\n
                2) 2NH3<\/sub> \u2192 N2<\/sub> + 3H2<\/sub><\/td>\nb) decomposition reaction<\/td>\n<\/tr>\n
                3) C2<\/sub>H4<\/sub> + H2<\/sub>O \u2192 C2<\/sub>H6<\/sub>O<\/td>\nc) displacement reaction<\/td>\n<\/tr>\n
                4) Fe2<\/sub>O3<\/sub> + 3CO \u2192 2Fe + 3CO2<\/sub><\/td>\nd) double displacement reaction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                Answer:<\/p>\n\n\n\n\n\n\n
                1) 2AgNO3<\/sub> + Na2<\/sub>CrO4<\/sub> \u2192 Ag2<\/sub>CrO4<\/sub> + 2NaNO3<\/sub><\/td>\nd) double displacement reaction<\/td>\n<\/tr>\n
                2) 2NH3<\/sub> \u2192 N2<\/sub> + 3H2<\/sub><\/td>\nb) decomposition reaction<\/td>\n<\/tr>\n
                3) C2<\/sub>H4<\/sub> + H2<\/sub>O \u2192 C2<\/sub>H6<\/sub>O<\/td>\na) combination reaction<\/td>\n<\/tr>\n
                4) Fe2<\/sub>O3<\/sub> + 3CO \u2192 2Fe + 3CO2<\/sub><\/td>\nc) displacement reaction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                Multiple Choice Questions:<\/span><\/p>\n

                1. Fe2<\/sub>O3<\/sub> + 2Al \u2192 Al2<\/sub>O3<\/sub> + 2Fe
                \nThe above reaction is an example of:
                \nA) Combination reaction
                \nB) Decomposition reaction
                \nC) Displacement reaction
                \nD) Double decomposition reaction
                \nAnswer:
                \nC) Displacement reaction<\/p>\n

                \"AP<\/p>\n

                2. What happens when dil. hydrochloric acid is added to iron filings? Choose the correct answer.
                \nA) Hydrogen gas and iron chloride are produced.
                \nB) Chlorine gas and iron hydroxide are produced.
                \nC) No reaction takes place.
                \nD) Iron salt and water are produced.
                \nAnswer:
                \nA) Hydrogen gas and iron chloride are produced.<\/p>\n

                3. 2PbO(s)<\/sub> + C(s)<\/sub> \u2192 2Pb(s)<\/sub> + CO2(g)<\/sub>
                \nWhich of the following statements are correct for the above chemical reaction?
                \ni) Lead is reduced
                \nii) Carbon dioxide is oxidized
                \niii) Carbon is oxidized
                \niv) Lead oxide is reduced
                \nA) (i) and (ii)
                \nB) (i) and (iii)
                \nC) (i), (ii) and (iii)
                \nD) all
                \nAnswer:
                \nB) (i) and (iii)<\/p>\n

                4. The chemical equation
                \nBaCl2<\/sub> + Na2<\/sub>SO4<\/sub> \u2192 BaSO4<\/sub> + 2NaCl represents following type of chemical reaction.
                \nA) displacement
                \nB) combination
                \nC) decomposition
                \nD) double-displacement
                \nAnswer:
                \nD) double-displacement<\/p>\n

                \"AP<\/p>\n

                5. The reaction of formation hydrogen chloride from hydrogen and chlorine repre\u00acsents following type of chemical reaction i
                \nA) decomposition
                \nB) displacement
                \nC) combination
                \nD) double-displacement
                \nAnswer:
                \nC) combination<\/p>\n

                9th Class Physical Science 6th Lesson Chemical Reactions and Equations InText Questions and Answers<\/h3>\n

                9th Class Physical Science Textbook Page No. 90<\/span><\/p>\n

                Question 1.
                \nWhat changes do you notice generally?
                \nAnswer:
                \nI noticed two types of changes generally. They are :<\/p>\n

                  \n
                1. Physical change,<\/li>\n
                2. Chemical change.<\/li>\n<\/ol>\n

                  Question 2.
                  \n“Coal is burnt”, “crackers are burnt” ………. changes Are they physical changes (or) chemical changes?
                  \nAnswer:
                  \nThey are all chemical changes.<\/p>\n

                  Question 3.
                  \nAre they (coal, crackers) temporary changes or permanent changes?
                  \nAnswer:
                  \nThey are permanent changes.<\/p>\n

                  \"AP<\/p>\n

                  Question 4.
                  \nHow do we know a chemical reaction has taken place?
                  \nAnswer:
                  \nWhile we observe the following things, we can conclude that a chemical reaction has taken place.<\/p>\n

                    \n
                  1. A change that changes state and colour of substance.<\/li>\n
                  2. A change that releases heat energy.<\/li>\n
                  3. A change which forms an insoluble substance as precipitate.<\/li>\n
                  4. A change that liberates a gas.<\/li>\n<\/ol>\n

                    9th Class Physical Science Textbook Page No. 92<\/span><\/p>\n

                    Question 5.
                    \nDo the atoms of each element on left side equal to the atoms of the element on the right side of the equation?
                    \nAnswer:
                    \nYes. The atoms of each element in left side are equal to the atoms of their corresponding element.<\/p>\n

                    9th Class Physical Science Textbook Page No. 94<\/span><\/p>\n

                    Question 6.
                    \nAre the atoms of all elements of reactants present in products?
                    \nAnswer:
                    \nYes. The atoms of all elements of reactants are present in products.<\/p>\n

                    \"AP<\/p>\n

                    Question 7.
                    \n2 C3<\/sub>H8<\/sub> + 10 O2<\/sub> \u2192 6 CO2<\/sub> + 8 H2<\/sub>O.
                    \nIs it a well balanced equation as per rules ? How do you say?
                    \nAnswer:
                    \nYes, it is a balanced equation.<\/p>\n\n\n\n\n\n\n
                    L.H.S.<\/td>\nR.H.S.<\/td>\n<\/tr>\n
                    Number of ‘C’ atoms = 6<\/td>\nNumber of ‘C’ atoms = 6<\/td>\n<\/tr>\n
                    Number of ‘H’ atoms = 16<\/td>\nNumber of ‘H’ atoms = 16<\/td>\n<\/tr>\n
                    Number of ‘O’ atoms = 20<\/td>\nNumber of ‘O’ atoms = 20<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                    9th Class Physical Science Textbook Page No. 105<\/span><\/p>\n

                    Question 8.
                    \nDid you notice the colour coating on silver and copper articles?
                    \nAnswer:
                    \nYes. I noticed. To prevent from corrosion they are colour coated like that.<\/p>\n

                    9th Class Physical Science Textbook Page No. 106<\/span><\/p>\n

                    Question 9.
                    \nHow can we prevent the spoiling of food?
                    \nAnswer:
                    \nThe spoilage of food can be prevented by adding preservatives like vitamin C and vitamin E.<\/p>\n

                    9th Class Physical Science 6th Lesson Chemical Reactions and Equations Activities<\/span><\/strong><\/p>\n

                    Activity – 1<\/span><\/p>\n

                    Question 1.
                    \nWrite an activity when calcium oxide reacts with water.
                    \nWhat type of reaction is this ? Write balanced chemical equation.
                    \nAnswer:<\/p>\n

                      \n
                    1. Take about 1 gm of quick lime (CaO) in a beaker.<\/li>\n
                    2. Add 10 ml of water to this.<\/li>\n
                    3. Touch the beaker with your finger.<\/li>\n
                    4. The beaker is hot.<\/li>\n
                    5. The reason is that the calcium oxide reacts with water and releases heat energy.<\/li>\n
                    6. Calcium oxide dissolves in water producing colourless solution [Ca(OH)2],<\/li>\n
                    7. Dip the red litmus paper in it.<\/li>\n
                    8. Red litmus paper changes into blue colour.<\/li>\n
                    9. We conclude that the solution obtained is a basic solution.<\/li>\n
                    10. It is a chemical combination reaction.
                      \nCaO(s)<\/sub> + H2<\/sub>O(l)<\/sub> \u2192 Ca(OH)2<\/sub><\/li>\n<\/ol>\n

                      Activity – 2<\/span><\/p>\n

                      Question 2.
                      \nWhat change do you observe by mixing of sodium sulphate solution and barium chloride solution?
                      \n(OR)
                      \nWhich type of reaction is this (mixing of sodium sulphate and barium chloride solutions)?
                      \nAnswer:
                      \n\"AP<\/p>\n

                        \n
                      • Take about 100 ml of water in a beaker.<\/li>\n
                      • Dissolve a small quantity of sodium sulphate (Na2<\/sub>SO4<\/sub>) in it.<\/li>\n
                      • Take about 100 ml of water in another beaker.<\/li>\n
                      • Dissolve a small quantity of barium chloride (BaCl2<\/sub>) in it.<\/li>\n
                      • Add these (Na2<\/sub>SO4<\/sub>, BaCl2<\/sub>) two solutions.<\/li>\n
                      • We will get a white precipitate of barium sulphate.
                        \nNa2<\/sub>SO4<\/sub> + BaCl2<\/sub> \u2192 BaSO4<\/sub>\u2193 + 2NaCl<\/li>\n
                      • It is a double displacement reaction.<\/li>\n<\/ul>\n

                        Activity – 3<\/span><\/p>\n

                        Question 3.
                        \nFormation of H2<\/sub> gas by the action of dil. HCl and Zn pieces.
                        \n(OR)
                        \nWhat happens if dilute HCl is added to zinc granules. Explain the process with an experiment. What type of reaction is this? Write the balanced chemical equation for this process.
                        \nAnswer:
                        \n\"AP
                        \nHydrogen gas experiment:<\/p>\n

                          \n
                        1. Take a few zinc granules in a conical flask.<\/li>\n
                        2. Add about 5 ml of dilute hydrochloric acid to the conical flask.<\/li>\n
                        3. Observe the changes in the conical flask.<\/li>\n
                        4. Keep a burning matchstick near the mouth of the conical flask.<\/li>\n
                        5. The light of burning matchstick is put off with ‘pop’ sound.<\/li>\n
                        6. This indicates the H2<\/sub> gas has released in this reaction.<\/li>\n
                        7. When we touch the bottom of the conical flask with our finger, we feel hot.<\/li>\n
                        8. So, this reaction produces heat.<\/li>\n
                        9. It is a displacement reaction
                          \nZn(s)<\/sub> + 2HCl(aq)<\/sub> \u2192 ZnCl2(aq)<\/sub> + H2(g)<\/sub><\/li>\n<\/ol>\n

                          Activity – 4 Chemical Combination<\/span><\/p>\n

                          Question 4.
                          \nWrite an activity on burning of magnesium ribbon in the presence of air.
                          \n(OR)
                          \nWrite an activity which shows burning of magnesium ribbon is a chemical combination reaction.
                          \nAnswer:
                          \n\"AP
                          \n1) Take about 3 cm long piece of magnesium ribbon.
                          \n2) Rub the magnesium ribbon with sand paper.
                          \n3) Hold it with a pair of tongs.
                          \n4) Burn it with a spirit lamp or burner.
                          \n5) Magnesium burns in oxygen by producing dazzling white flame and changes into white powder (magnesium oxide).
                          \n\"AP
                          \n7) In this reaction magnesium and oxygen combine to form a new substance magnesium oxide.
                          \n8) A reaction in which single product is formed from two or more reactants is known as chemical combination reaction.<\/p>\n

                          Activity – 5 Decomposition Reaction<\/span><\/p>\n

                          Question 5.
                          \nHow can you prove that CO2<\/sub> is released on heating CaCO3<\/sub>?
                          \n(OR)
                          \nWhen calcium carbonate is heated it releases certain gas. What is the gas that has been released? How do you identify that gas? Write the activity of this reaction.
                          \nAnswer:<\/p>\n

                            \n
                          • Take a pinch of Calcium Carbonate (lime stone) in a boiling tube.<\/li>\n
                          • Heat the boiling tube over the flame of spirit lamp or burner.<\/li>\n
                          • Now take a burning matchstick near the mouth of delivery tube.<\/li>\n<\/ul>\n

                            \"AP
                            \nHeating of calcium carbonate and testing the gas evolved with burning matchstick<\/p>\n

                              \n
                            • We can observe that the matchstick kept near the mouth of the boiling tube will be put off.<\/li>\n
                            • In the above activity, on heating CaC03, it decomposes to Calcium oxide (CaO) and Carbon dioxide (CO2<\/sub>).
                              \n\"AP<\/li>\n
                            • When a decomposition reaction is carried out by heating, it is called thermal decomposition reaction.<\/li>\n<\/ul>\n

                              Activity – 6<\/span><\/p>\n

                              Question 6.
                              \nWrite an activity to show that nitrogen dioxide (NO^ is released by heating of lead nitrate.
                              \n(OR)
                              \nWrite an activity which shows thermal decomposition reaction.
                              \nAnswer:
                              \n\"AP<\/p>\n

                                \n
                              1. Take about 0.5 g of lead nitrate powder in a boiling test tube.<\/li>\n
                              2. Hold the boiling tube with a test tube holder.<\/li>\n
                              3. Heat the boiling tube over a flame.<\/li>\n
                              4. We observe that on heating of lead nitrate brown fumes of nitrogen dioxide are released.<\/li>\n
                              5. On heating lead nitrate, it decomposes and gives lead oxide, oxygen and nitrogen dioxide.<\/li>\n<\/ol>\n

                                6) Reaction :
                                \n\"AP<\/p>\n

                                7) This is also an example for thermal decomposition reaction.<\/p>\n

                                Activity – 7<\/span><\/p>\n

                                Question 7.
                                \nWrite an activity to show dissociate of water into hydrogen and oxygen.
                                \n(OR)
                                \nWrite an activity showing decomposition of a compound in the presence of electricity.
                                \n(OR)
                                \nDraw a neat diagram representing electrolysis of water.
                                \nHow do you prove that water contains hydrogen and oxygen in the ratio of 2 : 1?
                                \n(OR)
                                \nExplain electrolysis of water.
                                \n(OR)
                                \nWhat are the materials required for the experiment to show the chemical decomposition of water ? Write the procedure of the experiment. Name the products which we get in this reaction.
                                \n(OR)
                                \nDraw a neat diagram showing the electrolytic decomposition reaction of water. Write the balanced chemical equation of the above reaction.
                                \nAnswer:
                                \n\"AP<\/p>\n

                                  \n
                                1. Take a plastic mug.<\/li>\n
                                2. Drill two holes at its base.<\/li>\n
                                3. Fit two ‘one holed rubber stoppers’ in these holes.<\/li>\n
                                4. Insert two graphite electrodes in these rubber stoppers.<\/li>\n
                                5. Connect the electrodes to 9V battery.<\/li>\n
                                6. Fill the mug with water, so that the electrodes are immersed.<\/li>\n
                                7. Add few drops of dilute sulphuric acid to water.<\/li>\n
                                8. Take two test tubes filled with water and invert them over the two graphite electrodes.<\/li>\n
                                9. Switch on the current and leave the apparatus undisturbed for sometime.<\/li>\n
                                10. We will notice that the liberation of gas bubbles at both the electrodes.<\/li>\n
                                11. These bubbles displace the water in the test tubes.<\/li>\n
                                12. We also observe that the volume of gas collected in the both test tubes is different.<\/li>\n
                                13. Once the test tubes are filled with gases take them out carefully.<\/li>\n
                                14. Test both the gases separately by bringing a burning candle near the mouth of each test tube.<\/li>\n
                                15. The gas which occupies high volume makes to burn with blue flame and put off candle flame with ‘puf sound is hydrogen gas.<\/li>\n
                                16. The gas which occupies low volume and makes to burn candle brightly is oxygen gas.<\/li>\n
                                17. In the above activity on passing the electricity, water dissociates to hydrogen and oxygen gases. This is called electrolytic composition reaction.
                                  \n\"AP<\/li>\n<\/ol>\n

                                  Activity – 8<\/span><\/p>\n

                                  Question 8.
                                  \nWrite an activity to observe silver bromide decomposes in the presence of sunlight.
                                  \n(OR)
                                  \nWrite an activity for photochemical reaction.
                                  \nAnswer:<\/p>\n

                                    \n
                                  • Take some quantity of silver bromide on a watch glass.<\/li>\n
                                  • When we observe the colour of silver bromide it is light yellow in colour.<\/li>\n
                                  • Place the watch glass in sunlight for sometime.<\/li>\n
                                  • Silver bromide decomposes to silver and bromine in sunlight.<\/li>\n
                                  • After sometime we observe that the colour of silver bromide changes into grey colour.<\/li>\n<\/ul>\n

                                    \"AP<\/p>\n