Question

For an endothermic reaction:
(A) \( q_p \) is negative.
(B) \( \Delta_rH \) is positive.
(C) \( \Delta_rH \) is negative.
(D) \( q_p \) is positive.
Choose the correct answer from the options given below:

• A. B and D
• B. C and D
• C. A and B
• D. A and C

Answer 1

The Correct Option is A

An endothermic reaction is characterized by the absorption of heat from the surroundings. In thermodynamic terms, this means that the enthalpy change of the reaction, denoted as \(\Delta_rH\), is positive. This is because the system absorbs heat, which results in an increase in enthalpy.

1. Understanding \(\Delta_rH\) for Endothermic Reactions:
   • For an endothermic reaction, \(\Delta_rH\) is positive since the system absorbs heat.
   • This eliminates option C, where \(\Delta_rH\) is stated as negative.
2. Understanding \(q_p\) for Endothermic Reactions:
   • \(q_p\) represents the heat absorbed or released at constant pressure. For an endothermic reaction, \(q_p\) is positive, consistent with the system absorbing heat.
   • This rule out option A, where \(q_p\) is stated as negative.

Therefore, the correct statements for an endothermic reaction are that \(\Delta_rH\) is positive and \(q_p\) is positive. Thus, the correct answer choice is B and D.