A positive value for ΔH for a chemical reaction is an indication of which of the following?

• A. The reaction produces more products than reactants.
• B. The reaction occurs spontaneously at all temperatures.
• C. The reaction is endothermic and absorbs heat from the surroundings.
• D. The reaction is exothermic and releases heat to the surroundings.

Answer: (C)

Verified step by step guidance

1. Understand that \( \Delta H \) represents the enthalpy change of a reaction, which indicates the heat absorbed or released during the reaction at constant pressure.
2. Recall that a positive value of \( \Delta H \) means the system absorbs heat from the surroundings, which characterizes an endothermic process.
3. Recognize that an endothermic reaction requires energy input, so it is not necessarily spontaneous at all temperatures; spontaneity depends on both enthalpy and entropy changes.
4. Note that the amount of products compared to reactants is not directly indicated by the sign of \( \Delta H \); it relates more to reaction equilibrium and kinetics.
5. Conclude that a positive \( \Delta H \) means the reaction is endothermic and absorbs heat from the surroundings, distinguishing it from exothermic reactions where \( \Delta H \) is negative.