C9: Chemical reaction.
1. Define physical change and chemical change with examples of each.
2. Write down the differences between physical change and chemical change.
3. What do you mean by word equation?
4. What are the drawbacks of word equations?
5. Define reactants and products.
6. What do you mean by formula equation or skeletal equation or unbalanced equation?
7. What do you mean by balanced equation?
8. What do you mean by balancing the chemical equation?
9. Why is it necessary to balance the chemical reaction?
Ans: According to law of conservation of mass, matter can neither be created nor be destroyed. During chemical reaction total mass of the reactant and products remains the same. Thus, for a complete chemical equation, the number of atoms of various elements on both sides should be made equal.
10. Write down the characteristics of chemical equations.
11. Write down the limitations of chemical equation.
12. What are the information that we can get from balanced chemical equation?
13. Define endothermic and exothermic chemical reaction with example of each.
14. Define catalyst.
15. What do you mean by positive and negative catalyst? Give one examples of each.
16. Write down the characteristics of catalyst.
17. What happens when iron is left in moist atmosphere for a long time? Write the chemical reaction involved and balance it. Also identify what type of chemical reaction is it.
18. Mention the factors that affect the rate of chemical reaction.
19. What are the two methods of balancing the chemical reaction?
20. Give an experiment to show that chemical change is irreversible.
Posts
Q.no.1.Namrata:The temporary change in which no new substance is formed and is usually reversible is called Physical change.Examples:changing of ice into water and back to ice,magnetizing iron substance,etc.
ReplyDeleteThe permanent change in which completely new substances are formed and is irreversible is called Chemical change.Examples:Rusting of iron,Burning of paper,etc.
Q.3.Namrata:The chemical reaction which is expressed by using the names of the substances involved rather than chemical formulae or symbols is called word equation.
ReplyDeleteQ.no.5.Namrata: Reactants are the compounds written on the left of arrowhead or equal sign and are present at the start of a chemical reaction.
ReplyDeleteProducts are the compounds or elements formed due to a reaction which are written on the right of arrowhead or equal sign and are present at the end of a chemical equation.
Q.no.14.Namrata: A catalyst is a substance which increases or alters the rate of a chemical reaction but itself remains unchanged chemically and in mass as well.
ReplyDeleteQ.no.11.Namrata: The limitations of a chemical equation are:
ReplyDelete1)Heat is given out or absorbed during the chemical reaction.
2)The time taken taken by the chemical reaction;A reaction
may or may not be complete which is not revealed by the
equation.
3)The rate of reaction whether slow or violent.
4)Conditions such as temperature, pressure and catalyst
affecting the reaction.
5)The physical states of substance concerned.
Q.no.14.A catalyst is a substance which alters the rate of a chemical reaction but itself remains unchanged,chemically ans in mass as well.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteQ.no.15.A catalyst which accelerates the rate of chemical reaction is called a positive catalyst.E.g. MnO2.
ReplyDeleteA catalyst which retards the rate of chemical reaction is called the negative catalyst.E.g. Glycerine.
Q.n.16.Roshan. Characteristics of catalyst are:
ReplyDelete1.Catalyst remains unchanged in its physical and chemical composition in the reaction.
2.Catalyst can't make impossible reaction possible.
3.Catalyst is always required in small amount.