Question 5 - MCQs from NCERT Exemplar - Chapter 1 Class 10 - Chemical Reactions and Equations

Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO ₄ and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?

(i) In beakers A and B, an exothermic process has occurred.

(ii) In beakers A and B, an endothermic process has occurred.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

(A) (i) only 

(B) (ii) only

(C) (i) and (iv) 

(D) (ii) and (iii)

Answer

Here, 

• Exothermic reactions are the ones where heat is evolved/given out .
• Endothermic reactions are the ones where heat is absorbed .

Now,

• Since the temperature of the solution in beakers A and B increased, an exothermic reaction took place in them.
• Also, because the temperature of the solution decreased in beaker C . So, endothermic reactio n took place

So, the correct option is (c) (i) and (iv)