{"id":4321,"date":"2021-02-02T11:49:01","date_gmt":"2021-02-02T06:19:01","guid":{"rendered":"http:\/\/conceptsdk.com\/?page_id=4321"},"modified":"2021-02-02T14:55:40","modified_gmt":"2021-02-02T09:25:40","slug":"chemical-reactions-and-equations-ncert-solutions","status":"publish","type":"page","link":"https:\/\/conceptsdk.com\/?page_id=4321","title":{"rendered":"Chemical Reactions and Equations-NCERT Solutions"},"content":{"rendered":"\n

NCERT Solutions<\/strong><\/p>\n\n\n\n

In Text Questions<\/strong> Page No: 6<\/strong><\/p>\n\n\n\n

1. Why should a magnesium ribbon be cleaned before it is burnt in air?<\/strong><\/p>\n\n\n\n

Ans: <\/strong>Magnesium is an very reactive metal. When stored, it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper for removing this layer so that the underlying metal can be exposed to air.<\/p>\n\n\n\n

2. Write the balanced equation for the following chemical reactions.<\/strong><\/p>\n\n\n\n

(a)  Hydrogen + Chlorine \u2192 Hydrogen chloride   <\/p>\n\n\n\n

(b)  Barium chloride + Aluminium sulphate \u2192 Barium sulphate + Aluminium chloride            <\/p>\n\n\n\n

(c)  Sodium + Water \u2192 Sodium hydroxide + Hydrogen<\/p>\n\n\n\n

Ans: (a)  H2 (g) + Cl2 (g) \u2192 2HCl (g)            <\/p>\n\n\n\n

(b)  3BaCl2 (s) + Al2(SO4)3 (s) \u2192 3BaSO4(s) + 2AlCl3 (s)            <\/p>\n\n\n\n

(c) 2Na(s) + 2H2O (l) \u2192 2NaOH (aq) + H2 (g)<\/p>\n\n\n\n

3. Write a balanced chemical equation with state symbols for the following reactions.<\/strong><\/p>\n\n\n\n

(a)  Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.            <\/p>\n\n\n\n

(b)  Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.<\/p>\n\n\n\n

Ans: (a)  BaCl2 (aq) + Na2SO4 (aq) \u2192 BaSO4 (s) + 2NaCl (aq)            <\/p>\n\n\n\n

(b)  NaOH (aq) + HCl (aq) \u2192 NaCL (aq) + H2O (l)<\/p>\n\n\n\n

Page No: 1<\/strong>0<\/p>\n\n\n\n

1. A solution of a substance \u2018X\u2019 is used for white washing.<\/strong><\/p>\n\n\n\n

(a)  Name the substance \u2018X\u2019 and write its formula.            <\/p>\n\n\n\n

(b)  Write the reaction of the substance \u2018X\u2019 named in (a) above with water.<\/p>\n\n\n\n

Ans: (a)  The substance \u2018X\u2019 is calcium oxide. Its chemical formula is CaO.            <\/p>\n\n\n\n

(b)  Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime).                   CaO (s) + H2O (l) \u2192 Ca(OH)2 (aq) <\/p>\n\n\n\n

Calcium Oxide (Quick Lime) + Water \u2192 Calcium Hydroxide (Slaked Lime)<\/p>\n\n\n\n

2. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.<\/strong><\/p>\n\n\n\n

Ans: Water contains two parts of hydrogen and one part\noxygen. Therefore, during the electrolysis of water the amount of hydrogen gas\ncollected in one of the test tubes is double than that of the oxygen produced\nand collected in the other test tube.<\/p>\n\n\n\n

Page No: 13<\/strong><\/p>\n\n\n\n

1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?<\/strong><\/p>\n\n\n\n

Ans: When an iron nail dipped in the copper sulphate solution than iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore the colour of the copper sulphate solution changes.<\/p>\n\n\n\n

The reaction involved here is:            Fe (s) + CuSO4 (aq) \u2192 FeSO4 (aq) + Cu (s)<\/p>\n\n\n\n

2. Give an example of a double displacement reaction other than the one given in Activity 1.10.<\/strong><\/p>\n\n\n\n

Ans: 2KBr (aq) + BaI2 (aq) \u2192 2KI (aq) + BaBr2 (aq)<\/p>\n\n\n\n

3. Identify the substances that are oxidised and the substances that are reduced in the following reactions.<\/strong><\/p>\n\n\n\n

(a)  4Na (s) + O2 (g) \u2192 2Na2O (s)           <\/p>\n\n\n\n

(b)  CuO (s) + H2 (g) \u2192 Cu (s) + H2O (l)<\/p>\n\n\n\n

Ans:<\/strong> (a)  Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced.            <\/p>\n\n\n\n

(b)  Copper oxide (CuO) is reduced to copper (Cu) while hydrogen (H2) gets oxidised to water (H2O).<\/p>\n\n\n\n

Exercise Chapter 01<\/strong><\/p>\n\n\n\n

Page No: 14<\/strong><\/p>\n\n\n\n

1. Which of the statements about the reaction below are incorrect?<\/strong><\/p>\n\n\n\n

2PbO (s) + C (s) \u2192 2Pb (s) + CO2 (g)            <\/p>\n\n\n\n

(a)  Lead is getting reduced.           <\/p>\n\n\n\n

(b)  Carbon dioxide is getting oxidised.            <\/p>\n\n\n\n

(c)  Carbon is getting oxidised.            <\/p>\n\n\n\n

(d)  Lead oxide is getting reduced.<\/p>\n\n\n\n

(i)     (a) and (b)            (ii)    (a) and (c)            (iii)  (a), (b) and (c)            (iv)   all<\/p>\n\n\n\n

Ans: (a)  (a) and (b)<\/p>\n\n\n\n

2. Fe2O3 + 2Al \u2192 Al2O3 + 2Fe<\/strong><\/p>\n\n\n\n

The above reaction is an example of a            <\/p>\n\n\n\n

(a)  combination reaction.            <\/p>\n\n\n\n

(b)  double displacement reaction.            <\/p>\n\n\n\n

(c)  decomposition reaction.            <\/p>\n\n\n\n

(d)  displacement reaction.<\/p>\n\n\n\n

Ans: (d)  displacement\nreaction.<\/p>\n\n\n\n

Page No: 15<\/strong><\/p>\n\n\n\n

3. What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer.<\/strong><\/p>\n\n\n\n

(a)  Hydrogen gas and iron chloride are produced.            <\/p>\n\n\n\n

(b)  Chlorine gas and iron hydroxide are produced.            <\/p>\n\n\n\n

(c)  No reaction takes place.            <\/p>\n\n\n\n

(d)  Iron salt and water are produced.<\/p>\n\n\n\n

Ans: (a)  Hydrogen gas and iron chloride are produced.<\/p>\n\n\n\n

4. What is a balanced chemical equation? Why should chemical equations be balanced?<\/strong><\/p>\n\n\n\n

Ans: A reaction which has an equal number of atoms of all\nthe elements on both sides of the chemical equation is called a balanced\nchemical equation.Chemical reaction should be balanced to follow law of\nconservation of mass.<\/p>\n\n\n\n

5. Translate the following statements into chemical equations and then balance them.<\/strong><\/p>\n\n\n\n

(a)  Hydrogen gas combines with nitrogen to form ammonia.           <\/p>\n\n\n\n

(b)  Hydrogen sulphide gas burns in air to give water and sulphur dioxide.            <\/p>\n\n\n\n

(c)  Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.           <\/p>\n\n\n\n

(d)  Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.<\/p>\n\n\n\n

Ans: (a)  3H2 (g) + N2 (g) \u2192 2NH3 (g)<\/p>\n\n\n\n

(b)  2H2S (g) + 3O2 (g) \u2192 2H2O (l) + 2SO2 (g)         <\/p>\n\n\n\n

(c)  3BaCl2 (aq) + Al2(SO4)3 (aq) \u2192 2AlCl3 (aq) + 3BaSO4 (s)           <\/p>\n\n\n\n

(d)  2K (s) + 2H2O (l) \u2192 2KOH (aq) + H2 (g)<\/p>\n\n\n\n

6.  Balance the following chemical equations.<\/strong><\/p>\n\n\n\n

(a)  HNO3 + Ca(OH)2 \u2192 Ca(NO3)2 + H2O           <\/p>\n\n\n\n

(b)  NaOH + H2SO4 \u2192 Na2SO4 + H2O           <\/p>\n\n\n\n

(c)  NaCl + AgNO3 \u2192 AgCl + NaNO3           <\/p>\n\n\n\n

(d)  BaCl2 + H2SO4 \u2192 BaSO4 + HCl<\/p>\n\n\n\n

Ans: (a)  2HNO3 + Ca(OH)2 \u2192 Ca(NO3)2 + 2H2O<\/p>\n\n\n\n

(b)  2NaOH + H2SO4 \u2192 Na2SO4 + 2H2O           <\/p>\n\n\n\n

(c)  NaCl + AgNO3 \u2192 AgCl + NaNO3           <\/p>\n\n\n\n

(d)  BaCl2 + H2SO4 \u2192 BaSO4 + 2HCl<\/p>\n\n\n\n

7. Write the balanced chemical equations for the following reactions.<\/strong><\/p>\n\n\n\n

(a)  Calcium hydroxide + Carbon dioxide \u2192nCalcium carbonate + Water  <\/p>\n\n\n\n

(b)  Zinc + Silver nitrate \u2192 Zinc nitrate + Silver           <\/p>\n\n\n\n

(c)  Aluminium + Copper chloride \u2192 Aluminium chloride + Copper    <\/p>\n\n\n\n

(d)  Barium chloride + Potassium sulphate \u2192nBarium sulphate + Potassium chloride<\/p>\n\n\n\n

Ans: (a)  Ca(OH)2 + CO2 \u2192 CaCO3 + H2O<\/p>\n\n\n\n

(b)  Zn + 2AgNO3 \u2192 Zn(NO3)2 + 2Ag          <\/p>\n\n\n\n

(c)  Al + 3CuCl2 \u2192 2AlCl3 + 3Cu          <\/p>\n\n\n\n

(d)  BaCl2+ K2SO4 \u2192 BaSO4 + 2KCl<\/p>\n\n\n\n

8. Write the balanced chemical equation for the following and identify the type of reaction in each case.<\/strong><\/p>\n\n\n\n

(a)  Potassium bromide (aq) + Barium iodide(aq) \u2192 Potassium iodide (aq) + Barium bromide(s)       <\/p>\n\n\n\n

(b)  Zinc carbonate (s) \u2192 Zinc oxide (s) + Carbon dioxide (g)    <\/p>\n\n\n\n

(c)  Hydrogen (g) + Chlorine (g) \u2192 Hydrogen chloride (g)       <\/p>\n\n\n\n

(d)  Magnesium (s) + Hydrochloric acid (aq) \u2192 Magnesium chloride(aq) + Hydrogen(g)<\/p>\n\n\n\n

Ans: (a)  2KBr (aq) + BaI2 (aq) \u2192 2KI (aq) + BaBr2 (s): Double displacement reaction<\/p>\n\n\n\n

(b)  ZnCO3 (s) \u2192 ZnO (s) + CO2 (g): Decomposition reaction       <\/p>\n\n\n\n

(c)  H2 (g) + Cl2 (g) \u2192 2HCl (g): Combination reaction        <\/p>\n\n\n\n

(d)  Mg (s) + 2HCl (aq) \u2192 MgCl2 (aq) + H2 (g) : Displacement Reaction<\/p>\n\n\n\n

9. What does one mean by exothermic and endothermic reactions? Give examples.<\/strong><\/p>\n\n\n\n

Ans: Chemical reactions that release energy in the form of heat, light, or sound are called exothermic reactions.<\/p>\n\n\n\n

Example:            C (g) + O2 (g) \u2192 CO2 + Heat Energy            <\/p>\n\n\n\n

Reactions that absorb energy or require energy in order to proceed are called endothermic reactions.            <\/p>\n\n\n\n

Example: N2 (g) + O2 (g) +Heat\u2192 2NO    <\/p>\n\n\n\n

10.  Why is respiration considered an exothermic reaction? Explain.<\/strong><\/p>\n\n\n\n

Ans: Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of heat energy.     <\/p>\n\n\n\n

C6H12O6 (aq) + 6O2 (g) \u2192 6CO2 (g) + 6H2O (l) + Energy<\/p>\n\n\n\n

11. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.<\/strong><\/p>\n\n\n\n

Ans: Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.            <\/p>\n\n\n\n

For Example: Decomposition Reaction: CaCO3 (s) + Heat \u2192CaO (s) + CO2 (g)<\/p>\n\n\n\n

Combination Reaction:            CaO (s) + H2O (l) \u2192 Ca(OH)2 (aq)<\/p>\n\n\n\n

Page No: 16<\/strong><\/p>\n\n\n\n

12.  Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity. <\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

13. What is the difference between displacement and double displacement reactions? Write equations for these reactions.<\/strong><\/p>\n\n\n\n

Ans: In a displacement reaction, a more reactive element replaces a less reactive element from a compound.<\/p>\n\n\n\n

For Example:            CuSo4 (aq) + Zn (s) \u2192 ZnSO4 (aq) + Cu (s)           <\/p>\n\n\n\n

In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.            <\/p>\n\n\n\n

For Example:            Na2SO4 (aq) + BaCl2 (aq) \u2192 BaSO4(s) + 2NaCl (aq)<\/p>\n\n\n\n

14. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.<\/strong><\/p>\n\n\n\n

Ans: 2AgNO3 (aq) + Cu (s) \u2192 Cu(NO3)2 (aq) + 2Ag (s)            Silver Nitrate + Copper \u2192 Copper Nitrate + Silver<\/p>\n\n\n\n

15. What do you mean by a precipitation reaction? Explain by giving examples.<\/strong><\/p>\n\n\n\n

Ans: A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.For Example:            Na2CO3 (aq) + CaCl2 (aq) \u2192 CaCO3 (s) + 2NaCl (aq)            Sodium Carbonate + Calcium Chloride \u2192 Calcium Carbonate + Sodium Chloride<\/p>\n\n\n\n

In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction.<\/p>\n\n\n\n

16.\u00a0Explain the following in terms of gain or loss of oxygen with two examples each.<\/strong><\/p>\n\n\n\n

(a)  Oxidation          (b)  Reduction<\/p>\n\n\n\n

Ans: Oxidation Reaction:<\/strong> It is a chemical reaction in which gain of oxygen or loss of hydrogen takes place <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Reduction Reaction: <\/strong>It is a chemical reaction in which loss of oxygen or gain of hydrogen takes place <\/p>\n\n\n\n

17.\u00a0A shiny brown-coloured element \u2018X\u2019 on heating in air becomes black in colour. Name the element \u2018X\u2019 and the black coloured compound formed.<\/strong><\/p>\n\n\n\n

Ans:<\/strong> \u2018X\u2019 is copper (Cu) and the black-coloured compound formed is copper oxide (CuO). The equation of the reaction involved on heating copper is given below.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

18.\u00a0 Why do we apply paint on iron articles?<\/strong><\/p>\n\n\n\n

Ans: <\/strong>Iron articles are painted because it prevents them from rusting. When painted, the contact of iron articles from moisture and air is cut off. Hence, rusting is prevented.<\/p>\n\n\n\n

19.Oil and fat containing food items are flushed with nitrogen. Why?<\/strong><\/p>\n\n\n\n

Ans: <\/strong>Oil and fat containing food items flushed with nitrogen because nitrogen acts as an antioxidant and it prevent them from being oxidised.<\/p>\n\n\n\n

20.\u00a0Explain the following terms with one example each.<\/strong><\/p>\n\n\n\n

 (a)  Corrosion              (b)  Rancidity<\/p>\n\n\n\n

Ans:<\/strong> Corrosion is defined as a process where materials, usually metals, deteriorate as a result of a chemical reaction with air, moisture, chemicals, etc.<\/p>\n\n\n\n

For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.<\/p>\n\n\n\n

  4Fe + 3O2 + nH2O \u2192 2Fe2O3.2H2O<\/p>\n\n\n\n

Rancidity<\/strong> is the process of oxidation of fats and oils that can be easily noticed by the change in taste and smell is known as rancidity.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/p>\n\n\n\n

For example, the taste and smell of butter changes when kept for long<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

NCERT Solutions In Text Questions Page No: 6 1. Why should a magnesium ribbon be cleaned before it is burnt in air? Ans: Magnesium is an very reactive metal. When stored, it reacts with oxygen to form a layer of magnesium oxide on its surface. This layer of magnesium oxide is quite stable and prevents further […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"class_list":["post-4321","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/pages\/4321","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/conceptsdk.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4321"}],"version-history":[{"count":5,"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/pages\/4321\/revisions"}],"predecessor-version":[{"id":4375,"href":"https:\/\/conceptsdk.com\/index.php?rest_route=\/wp\/v2\/pages\/4321\/revisions\/4375"}],"wp:attachment":[{"href":"https:\/\/conceptsdk.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4321"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}