Question 1 - Case Based Questions (MCQ) - Chapter 3 Class 10 - Metals and Non-Metals

Study the given table and answer any four questions from (a) to (e):  A student took the samples of four metals A, B, C and D and added the following solutions one by one. The results  obtained have been tabulated as follows: 

(a) Choose the most reactive metal:  

(i) A 

(ii) B  

(iii) C 

(iv) D  

Answer

• According to the reactivity series , among the 4 salts given, Zinc Sulphate is the most reactive . 
• Since no metals react with it, we consider the next most reactive solution, Iron (II) Sulphate .
• Since only B is able to displace Iron from Iron (II) Sulphate, it is the most reactive among A,B,C,D

So, the correct answer is (i) B

(b) Which of the following will displace Cu from its  solution of sulphate:  

(i) A only 

(ii) B only  

(iii) Both A and B 

(iv) None of the above

Answer

From the given table, it is seen that 

• A is able to displace Cu from Copper (II) Sulphate.
• Since B is more reactive than A , it will also be able to displace Cu.

So, the correct answer is (iii) Both A and B

(c) Which is the correct decreasing order of reactivity?   

(i) B > A > C > D 

(ii) A > B > D > C  

(iii) D > B > A > C 

(iv) B > A > D > C  

Answer

Let us go in order of most reactive to least reactive salt solutions.

• Zinc solution is the most reactive salt solution here. But no metal reacts with it . 
• B is the most reactive element as it is able to displace Iron from its salt solution .
• A is able to displace copper from its salt solution.
• C is able to displace Silver from its salt solution.
• D is the least reactive element, since it does not react at all .

So, the correct option is (i) B > A > C > D

(d) The gas produced when dil. HCl is added to a  reactive metal:  

(i) Oxygen 

(ii) nitrogen  

(iii) hydrogen 

(iv) none of the above

Answer

The reaction of a reactive metal with dil HCl is as follows:

2M + 2dil HCl→ 2MCl+ H ₂ ↑

Where M is any reactive metal.

So, the correct option is (iv) Hydrogen

(e) On the basis of sequence of reactions, identify the  most and least reactive elements.  

A + BX → AX + B  

C + AY → CY + A  

(i) Most reactive: C; Least reactive: B  

(ii) Most reactive: B; Least reactive: C  

(iii) Most reactive: A; Least reactive: B  

(iv) Most reactive: B; Least reactive: A  

Answer

• A is able to displace B from its salt solution BX. So, A is more reactive than B
• C is able to displace A from its salt solution AY. So, C is more reactive than A and therefore, also more reactive than B

Hence, C is most reactive and B is least reactive 

So, the correct option is (i) Most reactive: C; Least reactive: B