Question 3 - Case Based Questions (MCQ) - Chapter 2 Class 10 - Acids, Bases and Salts

Suhana takes three beakers A, B and C filled with aqueous solutions of glucose, alcohol and hydrochloric acid  respectively as shown in the following figure:  

(a) Which of the following statements is correct in  terms of glowing of the bulb when the switch is ON?   

(i) Bulb A and B do not glow but bulb C glows.  

(ii) Bulb A and C do not glow but bulb B glows.  

(iii) Bulb B and C do not glow but bulb A glows.  

(iv) All the bulbs glow.  

Ans. 

We know that Acids and bases conduct electricity in Water. They conduct electricity because they form ions in water.

Here,

• Since Glucose is neither an acid or base, it does not conduct electricity. So, it will not glow.
• Alcohol forms hydrogen bonds with water so it does not dissociate to give ions. So, the bulb will not glow .
• Both glucose and alcohol are non electrolytes i.e. they do not produce ions when dissolved in water.

Due to this, they are unable to conduct electricity and hence, the bulbs A and B do not glow.

On the other hand, dil HCl is an electrolyte i.e. it produces ions when dissolved in water. So, they are able to conduct electricity and hence, the bulb C glows.

So, the correct answer is (i) Bulb A and B do not glow but bulb C glows.

(b) The bulb glows in a solution depending on  whether the solution is:  

(i) acidic 

(ii) an electrolyte  

(iii) basic 

(iv) a non electrolyte  

Ans.

An electrolyte is a solution which is able to produce ions in aqueous solution.

These ions are responsible for the conduction of electricity .

Therefore, a bulb will only glow if we take an electrolyte because only then ions will be produced and the solution will be able to conduct electricity.

Note : Both Acids and Bases are electrolytes.

So, the correct answer is (ii) an electrolyte  

(c) Which of the following are present in a dilute  aqueous solution of hydrochloric acid?  

(i) H ₃ O ⁺ + Cl ^– 

(ii) H ₃ O ⁺ + OH ^–   

(iii) Cl ^– + OH ^–  

(iv) Unionized HCl  

Ans. 

Aqueous solution of HCl means HCl in water.

So, the reaction looks like 

A dilute aqueous solution of hydrochloric acid is an electrolyte and produces H ₃ O ⁺ and Cl ^- ions .  

So, the correct answer is (i)

(d) Which of the following statement is true if alcohol  is replaced with NaOH solution:   

(i) The bulb glows in alcohol but not in NaOH solution.  

(ii) The bulb will glow in NaOH solution but not in  alcohol  

(iii) The bulb does not glow in alcohol and neither will it  glow in NaOH solution.  

(iv) The bulb glows in NaOH solution as well as in alcohol.  

Ans. 

Here,

• Alcohol forms hydrogen bonds with water so it does not dissociate to give ions. So, the bulb will not glow .
• And NaOH is a base. Since base is an electrolyte , it is able to produce ions and thereby conduct electricity.

Therefore, the bulb will glow if we replace alcohol with NaOH.

So, the correct answer is (ii) The bulb will glow in NaOH solution but not in  alcohol.