Important Question Answers: 

Q1. Write the general Name of CaO (s).

Ans: ​ The general Name of Calcium oxide is Quick lime. 

Q2. By which physical states, reactant and product are shown in a chemical reaction.

Ans: 

 (s) – For Solid

 (g) – For gas

 (l) – For liquid

 (aq) – For Aqueous (Solution) 

Q3. What happens when a magnesium ribbon is burnt in presence of Oxygen?

Ans:  when a magnesium ribbon is burnt in presence of Oxygen, it gets converted to magnesium oxide.

Q4. Why is respiration considered an exothermic reaction? Explain.

Ans:  Respiration takes place in our body cells regularly. This is an exothermic reaction. After breaking down of obtained carbohydrate from food converts into glucose, which provides energy to our body combine with oxygen. Hence the exothermic reaction gives energy in very large quantity so the respiration is also called an exothermic reaction.

Q5. Name the reaction in which two or more than two reactants form one product to combine each other. Write a balance reaction of this reaction.

Ans: Combination reaction.

           CaO(S)    +     H₂O(l)   →   Ca(OH)₂(aq)

           (Quick lime)                         (Slaked lime)

Q6. A solution of a substance ‘X’ is used for white washing.

(i)Name the substance ‘X’ and write its formula.

(ii)Write the reaction of the substance ‘X’ named in (i) above with water.

(iii)Write it’s an industrial use.

(iv)Name the substance which chemical formula is same as ‘X’.

Ans:

(i)‘X’ is Calcium oxide Or Quick lime. Its formula is CaO.

(ii) CaO(S)    +     H₂O(l) →  Ca(OH)₂(aq)

    (Quick lime)                     (Slaked lime)

(iii)In cement industry.

(iv)Marble.   

Q7.Write two reactions name which are the effects of oxidation reaction in everyday life.

Ans: 

(i)    Corrosion.

(ii)    Rancidity 

Q8.A white substance, which is insoluble in water, is formed by reaction between sodium sulphate and barium chloride.

(i)What is called such insoluble substance?

(ii)Name this white substance.

(iii)Show the products of this reaction with writing a balance equation.

(iv)What is called this type of reaction?

Ans: 

(i)Precipitate.

(ii)Barium sulphate (BaSO₄ )

(iii)

(iv)Double displacement reaction.

Q9.  What is rancidity?

Ans: Some fat or oil containing food materials are left for a long time, they are oxidized and become rancid. Their smell and taste change. This change is called rancidity.

Q10.With which gas, Oily or fat containing food like chips are packed to kept for a long time. Why?

Ans: Nitrogen, preventing from getting oxidized.

Q11.What do you mean by a precipitation reaction? Explain by giving examples.

Ans:  Such a reaction which produces insoluble substance. This formed insoluble substance is known as a precipitate. Any reaction that produces a precipitate is called precipitation reaction.

For example: A white substance of Barium sulphate, which is insoluble in water, is formed by reaction between sodium sulphate and barium chloride.

Q12.A shiny brown coloured element ‘X’ on heating in air becomes black in colour.

(i)Name the element ‘X’.

(ii)Name the black coloured compound formed.

 Ans: 

(i)‘X’ is Aluminium.

(ii)Al₂ O₃

Q13. Write the methods to prevent iron articles from corrosion.

Ans:

(i)By galvanization.

(ii)Painting and greasing.

(iii)Oiling and by plastic coating. 

Q14.A reddish brown element X on heating converted into a black coloured compound Y, which turns phenolphthalein pink.

(i) Identify compound ‘Y’.

(ii) Identify the element ‘X’.

(iii) Give inter conversion reaction of X and Y.

Ans: 

(i)   compound ‘Y’ is copper oxide.

(ii)   Element ‘X’ is copper.

(iii)   2 Cu   +   O₂    → Heat     2Cuo

Q15.What is rancidity? Give four methods to slow down it.

Ans: Some fat or oil containing food materials are left for a long time, they are oxidized and become rancid their smell and taste change .this change is called rancidity.