Question

What does a positive AH tell about a reaction?

A. The reaction is exothermic.
B. The reaction has heat as a product.
C. The reaction is endothermic.
D. The reaction has no activation energy.

Answer 1

`\boxed {\boxed {\sf C. \ The \ reaction \ is \ endothermic}}`

Step-by-step explanation:

There are two main types of reactions classified according to heat: exothermic and endothermic.

• Exothermic: heat is released from the system
• Endothermic: heat is absorbed into the system

The ΔH is the change in enthalpy. It is the difference between the heat of the products and the reactants (ΔH = heat of products - heat of reactants). It helps us describe a system's change in heat and classify reactions as exothermic or endothermic.

• Exothermic: the products have less energy because heat is released. The change in enthalpy or ΔH is negative.
• Endothermic: the products have more energy because heat is absorbed. The change in enthalpy or ΔH is positive.

In this problem, the change in enthalpy is positive. The change in enthalpy doesn't refer to heat as a product or activation energy. Therefore, the reaction must be endothermic.

Answer 2

C

Step-by-step explanation:

An endothermic reaction has a positive enthalpy change (∆H> 0).

An endothermic reaction is where the energy of the products is higher than that of the reactants.

∆H= energy of products -energy of reactants

Thus, ∆H is positive since the value of the energy of products is greater than that of the reactants.

Exothermic reactions have a negative ∆H.

In an endothermic reaction, heat is absorbed and thus if we were to include heat in teh chemical equation, it would be part of the reactants not products.

∆H does not indicate the amount of activation energy (Ea). All reactions have activation energy (exothermic and endothermic reactions). Activation energy is the minimum amount of energy required for the reaction to proceed.