Chemical reactions worksheet answer.

     

Introduction to Chemical Reactions worksheet answer:-


Today in this article I will discuss on the  topic Introduction to 'Chemical Reactions Worksheet Answers'.
 

What is  Physical change  of matters?


Answer:- A process in which external features like size,shape,states of the matters are changed but no internal features like new atoms or molecules created or matters do not occured any new property   is known as physical change. e.g; when water is freezed at 0°C its state of matter changes from liquid(water) to solid(ice) but there is neither new molecules or new property are formed as water is H₂O , on the other hand ice is also H₂O, So there is no new substance is produced, so it is a physical change.



    What is Chemical change?

    Answer:- A process in which total internal property of matters changes means after the change a completely new property substance is produced i.e;all new elements,atoms or molecules are produced and old property of the first substance completely changed is known as chemical change.e.g; If iron is kept outside in an open space for a long time a red layer grows up on it ,it is called rusting of iron, actually when iron is kept in outside , slowly it reacts with oxygen in catalytic presence of moisture to produce reddish brown iron oxide[ferric oxide(Fe₂O₃)] which we call rust and the complete phenomenon is known as rusting.


    Chemical reactions worksheet answer.



    What is chemical reaction?


    Answer:- A chemical reaction is a process
    in which one or more compounds or elements which are called reactants converted into completely new one or more compounds which are known as products by means of either combination or decomposition.e.g;When carbon is burnt in presence of excessive air it produces carbon dioxide(CO₂)
    The reaction can be given by:-
        C+O₂—----> CO₂ ,

    Now we will discuss on Indentifying types of chemical reactions worksheet.

    What are types of chemical reactions ?


    (i) Combination reaction:-

    When one or more elements or compounds of the reactants combines themselves to form a new compound i.e a;product in a chemical reaction then it is called combination reaction.
     
       2H₂(g) +  O₂(g) —---> 2H₂O(aq)
      This is a combination reaction.

    e.g; When hydrogen gas(H₂) reacts with oxygen (O₂) it produces water.The reaction can be given by:-


    (ii)Decomposition Reaction:-

    A chemical reaction where a compound or a molecule splits up into one or more compounds (in products) under certain definite conditions when which may be either heating or in presence of catalyst is known as decomposition reaction. When potassium chlorate (Kclo₃) is heated it breaks and produces potassium chloride(Kcl) and oxygen(O₂). The reaction can be given by:-


    Chemical reactions worksheet answer.



    (iii)Displacement Reaction:-

    A chemical reaction in which one more reactive element displaces comparatively less reactive element from its compound is known as displacement reaction.e.g; When sodium reacts with silver nitrate solution it displaces silver from AgNO₃ and produces sodium nitrate(NaNO₃).The reaction can be given by:-
      Na(s)+AgNO₃(s)—------->NaNO₃(s) + Ag(s)

    (iv)Double displacement Reaction:-

    A chemical reaction in which two elements displace each other from their compounds to form new products is called double displacement reaction.
    e.g; When sodium sulphide reacts with hydrochloric acid it produces sodium chloride and hydrogen sulphide gas.
      The reaction can be given by:-
    Na₂S(s) + HCl(aq)—--> Nacl(s)+ H₂S(g)

    (v)Oxidation Reaction :-

    If oxygen is added and hydrogen is removed in a chemical reaction ,then the reaction is called oxidation reaction.e.g;  Carbon combines with oxygen and produces carbon dioxide.Here carbon is oxidised to carbon dioxide.

    Chemical reactions worksheet answer.


    Again, when hydrogen sulphide (H₂S) reacts with bromine then hydrobromic acid(HBr) is produced and sulphur is released from H₂S.

    Chemical reactions worksheet answer.

    In this case, sulphur is oxidised from H₂S to s ,Since from defination we know that remove of hydrogen is oxidation.Here hydrogen is released from H₂S to S.


    (vi)Reduction reaction :-

    If oxygen is released and hydrogen is added in a chemical reaction, then the reaction is called reduction reaction.e.g; When carbon reacts with cuprous oxide it displaces copper from copper oxide(Cuo) and produces carbon monoxide. The reaction can be given by:-

    Chemical reactions worksheet answer.


    In this case, cuprous oxide(Cuo) is reduced to copper,by defination we find that removal of oxygen is reduction, so,Cu is reduced.When hydrogen sulphide reacts with chlorine ,Hcl is is produced and sulphur is liberated.

         H₂S(g)+Br₂(s)--------->2HBr(aq)+ s(s)
    Here, H₂ is added to chlorine so,by difination cl is reduced to Hcl.

    (vii) Redox Reaction:-

    If oxidation and reduction reaction take place simultaneously in a chemical reaction, then ,the reaction is called redox reaction.

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    FREQUENTLY ASKED QUESTIONS:-
    What are four types of chemical reactions?

    Answer:- Four types of chemical reactions are :-(i) Combination reaction.(ii) Decomposition.(iii) Displacement reaction.(iv) Double displacement reaction.

    What are exothermic and endothermic reactions?

    Answer:-The chemical reactions in which heat is evolved, are called exothemic reaction.e.g;when carbon reacts with oxygen,carbondioxide is produced along with a lots of heat which is an exothermic reaction.The reaction can be written as:- C + O₂ -----> CO₂ + Ξ” (heat).The reactions in which heat is absorbed are called endothermic reactions.e.g;When calcium cabonate (CaCO₃) is heated it splits up into calcium oxide (CaO) and carbon dioxide absorbing lots of heat and the reaction is termed as an endothermic reaction,which can be shown as:- CaCO₃ + Ξ” (heat) -----> CaO + CO₂

    Why decomposition reaction is called the reverse of combination reaction?

    Answer:- In combination reactions, two or more elements or compounds combine together to form a new product where as in decomposition reaction one compound breaks under some definite conditions to form two or more compounds,so decomposition reaction is called the reverse of combination reaction.

    Is there any reaction takes place,if we dipped a Copper nail into ferrous sulphate (Feso₄) solution ? If not then explain.

    Answer:- In this case,there will be no reaction takes place as we find that in reactivity series of metal Copper is placed below iron (Fe),means iron is more reactive than copper so copper is unable to displace iron from ferrous sulphate (Feso₄) solution,thats why there takes place no reaction,which can be expressed as :- Cu + Feso₄ -----> No reaction

    Some examples of chemical reactions.

    Answer:-Some examples of chemical reactions are :- (i) 2H₂(aq) + O₂(aq) ----> 2H₂O (aq) (ii) CO₂(g) + H₂O(aq)----->H₂CO₃(aq) (iii)NaOH(aq)+Hcl(aq)---->Nacl(s)+H₂O(aq)

    What types of chemical reactions show alkane,alkene and alkyne.

    . Answer:- Alkane shows substitution reaction while alkene and alkyne show addition reactions.








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