Question 5 - Case Based Questions (MCQ) - Chapter 1 Class 10 - Chemical Reactions and Equations

In the following chemical reaction zinc oxide reacts with carbon to produce zinc metal and  carbon monoxide.’’

ZnO + C → Zn + CO  

(a) Name the substance getting oxidised and reduced  in the above reaction:   

(i) C and ZnO 

(ii) Zn and C  

(iii) ZnO and CO 

(iv) CO and ZnO  

Ans. 

ZnO + C → Zn + CO 

Now,

• Addition of oxygen is known as oxidation 
• Removal of oxygen is known as reduction.

Since in the equation

• Oxygen is being removed from ZnO
•  and is added to C.

Therefore, C is undergoing oxidation and ZnO reduction. 

So, the correct answer is (i) C and ZnO  

(b) Name the type of reaction:  

(i) oxidation reaction  

(ii) reduction reaction  

(iii) redox reaction  

(iv) decomposition reaction  

Ans .

Since both oxidation and reduction is taking place in this reaction, it is a redox reaction.

So, the correct answer is (iii) redox reaction  

(c) The reduction reaction involves:  

(i) gain of electrons  

(ii) loss of electrons  

(iii) increase in oxidation state  

(iv) addition of oxygen  

Ans. 

So, the correct answer is (i) gain of electrons

(d) Which of the following is the effect of oxidation  reaction in everyday life:  

(i) Precipitation  

(ii) Fermentation  

(iii) Corrosion  

(iv) Hydrogenation of oil  

Ans. 

Let’s look at each of the reaction , one by one

1. Precipitation reaction reaction is not an oxidation reaction because this simply involves the formation of an insoluble substance (precipitate).
2. Fermentation breaking down of food in the absence of oxygen
3. Corrosion involves the oxidation of iron to form rust
4. Hydrogenation of oil is not an oxidation reaction because in this, hydrogen atoms are added over the double bonds of hydrocarbons. 

So, the correct answer is (iii) Corrosion

(e) The reactions used in black and white photography:   

(i) Decomposition of silver bromide  

(ii) Decomposition of silver chloride  

(iii) Both  

(iv) None of the above  

Ans. 

Black and white photography is looks like

• The photographic papers are prepared by using silver chloride and silver bromide which are initially white in color.
• On exposure to air, AgCl and AgBr decompose and lose their color and black and white images are obtained.

So, the correct answer is (iii) Both