Question

When the solids Ba(OH)2 and NH4SCN are mixed, a solution is produced and the temperature drops. \[ {Ba(OH)}_2(s) + 2{NH}_4{SCN}(s) \rightarrow {Ba(SCN)}_2(aq) + 2{NH}_3(g) + 2{H}_2{O}(l) \] Which statement about the energetics of this reaction is correct?

• A. The reaction is endothermic and \( \Delta H \) is negative
• B. The reaction is endothermic and \( \Delta H \) is positive
• C. The reaction is exothermic and \( \Delta H \) is negative
• D. The reaction is exothermic and \( \Delta H \) is positive

Hint:

In endothermic reactions, the system absorbs heat, which leads to a temperature decrease in the surroundings.

Answer 1

The Correct Option is B

Since the temperature drops during the reaction, it indicates that the system absorbs heat from the surroundings. This type of reaction is called endothermic, as heat is absorbed rather than released. In an endothermic reaction, the enthalpy change (\( \Delta H \)) is positive because the system's internal energy increases due to the absorption of heat.

Therefore, \( \Delta H \) is positive, indicating that the reaction is endothermic.