Which of the following is(are) true for an exothermic reaction? [H = enthalpy]
A) ƒ´H¢X > 0 B) ƒ´H¢X < 0
C) Hreactants > Hproducts
D) Hreactants < Hproducts
E) Hreactants = ƒ´H¢X
The square means delta.
To determine the correct answer choice, let's understand the concept of an exothermic reaction first. An exothermic reaction is a chemical reaction that releases energy in the form of heat.
Answer choices A and B are related to change in enthalpy (∆H).
∆H is the difference in enthalpy between the reactants and the products of a chemical reaction. If ∆H is positive, it means the reaction is endothermic (absorbs energy). If ∆H is negative, it means the reaction is exothermic (releases energy).
So, for an exothermic reaction:
- ∆H is negative, which means option A (ƒ´H¢X > 0) is not true.
- ∆H is less than 0, which means option B (ƒ´H¢X < 0) is true.
Answer choices C and D compare the enthalpy of the reactants and products.
For an exothermic reaction, the enthalpy of the reactants is greater than the enthalpy of the products. This is because the reaction releases energy, so the products have a lower enthalpy. Therefore, option C (Hreactants > Hproducts) is not true, and option D (Hreactants < Hproducts) is true.
Answer choice E compares the enthalpy of the reactants and the change in enthalpy (∆H) of the reaction. However, these two quantities are not directly related. They can have the same sign, but they are not equal. Therefore, option E (Hreactants = ƒ´H¢X) is not true.
In conclusion, the correct answer is:
B) ƒ´H¢X < 0
D) Hreactants < Hproducts