NCERT Solutions for Class 10 Science Chapter 1

Free NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations in PDF form to download. NCERT Solutions for Class 10 Science all chapters and answers given with in the chapters are also given in PDF form to download. Download NCERT Books for class 10 in PDF form.

NCERT Solutions for Class 10 Science Chapter 1

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Class 10 Science Chapter 1 Intext Questions Page 6, 10, 13 in English Medium

Class 10 Science Chapter 1 Exercises Question 1 to Question 9 in English Medium

Class 10 Science Chapter 1 Exercises Question 10 to Question 20 in English Medium

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Class 10 Science Chapter 1 Intext Questions Page 6, 11, 15 in Hindi Medium

Class 10 Science Chapter 1 Exercises Question 1 to Question 8 in Hindi Medium

Class 10 Science Chapter 1 Exercises Question 9 to Question 20 in Hindi Medium

Hindi Medium

Important Questions with Answers on Chemical Reactions and Equations

  • Question 1:
    What is meant by a skeletal chemical equation? Using suitable chemical reaction, differentiate between a skeletal chemical equation and a balanced chemical equation.
    Answer 1:
    If the number of atoms of any element in a chemical equation is not equal on both sides, then it is a skeletal equation. For example:Class 10 Science - Chemistry Solutions 1Here, the number of chlorine and hydrogen atoms are not equal on both sides.
    In a Balance equation, the numbers of atoms of different elements on both sides of a chemical equation are equal. For example:Class 10 Science - Chemistry Solutions 2
  • Question 2:
    What is a thermochemical equation? Give two examples.
    Answer 2:
    Most chemical reactions are accompanied by either evolution or absorption of heat. These reactions are known as exothermic and endothermic reaction reactions respectively. Such an equation in which information about heat change is included is called a thermochemical equation. It is very important in such a case to indicate the physical sate of the various species involved
    Example are:Class 10 Science - Chemistry Solutions 3
  • Question 3:
    Differentiate between an exothermic and endothermic reaction. Write one example for each of these reactions in the form of balanced chemical equation.
    Answer 3:
    We know that constituent elements in a compound are bound by chemical bonds. During a chemical change, when bonds between the constituents of the reactants are broken, energy is consumed whereas energy is given out when the bonds are formed as in the case of products. Thus, depending on whether overall energy is given out or consumed, the reaction is either exothermic or endothermic.
    Exothermic reactions: Chemical reactions in which energy is evolved (or given out) are known as exothermic reaction. For example:Class 10 Science - Chemistry Solutions 4Formation of ammonia form nitrogen and hydrogen is an exothermic reaction.Class 10 Science - Chemistry Solutions 5Endothermic Reaction: Reactions in which energy is absorbed are called endothermic reaction reactions. For example, When carbon reacts with sulphur , heat is absorbed during the process.Class 10 Science - Chemistry Solutions 6Formation of nitric oxide (NO) is an endothermic reaction.Class 10 Science - Chemistry Solutions 7
  • Question 4:
    Explain the following terms with examples in each case:
    (i) Oxidation and  (ii) Reduction.
    Answer 4:
    (i) Oxidation: it us a process  (a) in which oxygen or any electronegative element is added up or (b) hydrogen or any electropositive element is removed. Examples are:
    (a)Sulphur burns in the air with a blue flame to form sulphur dioxide. Here oxygen is added up to sulphur.Class 10 Science - Chemistry Solutions 8(b) Hydrogen sulphide combines with iodine to give hydrogen iodine and sulphur.Class 10 Science - Chemistry Solutions 9(ii) Reduction:  It is a process in which (a) Hydrogen or an electropositive element is added up. (b) Oxygen or electronegative element is removed. Examples are:
    (a)Hydrogen reacts with chlorine to form hydrogen chloride.Class 10 Science - Chemistry Solutions 10(b)Copper oxide is reduce with hydrogen.Class 10 Science - Chemistry Solutions 11
  • Question 5:
    What is a Redox reaction?
    Answer 5:
    A chemical reaction in which one substance is oxidised and the other is reduced is called a redox reaction. All oxidation-reduction reactions are redox reaction. In a chemical reaction, a substance gets oxidised only when another substance is present, which gets reduced.Class 10 Science - Chemistry Solutions 12Question 6:
    Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
    Answer 6:
    When an iron nail is dipped in copper sulphate solution, it becomes brownish in colour and colour of copper sulphate fades due to the following reaction:Class 10 Science - Chemistry Solutions 13In this reaction iron has replaced copper from its solution. Thus, amount of copper sulphate decreases and its colour fades.
  • Question 7:
    Why is respiration considered an exothermic reaction? Explain.
    Answer 7:
    During digestion, food is broken down into simpler substances. Food like rice, potato and bread are made up of carbohydrates. These carbohydrates are further broken down into glucose. Glucose during respiration (inhalation of oxygen) is oxidised with the liberation of energy as shown below:Class 10 Science - Chemistry Solutions 14Thus, respiration is an exothermic process.


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