Consider the reaction shown:
452 kcal + 4 PCl5 (s) �¨ P4 (s) + 10 Cl2(g)
This reaction is ________ because the sign of ĢH is ________.
A) exothermic; neither positive nor negative
B) endothermic; positive
C) endothermic; negative
D) exothermic; positive
E) exothermic; negative
I answered one of these questions MUCH further up before I noticed the plethora of questions you have posted and I quit. No one here will do your homework for you. If you wish to go back and look at each of your questions, then post what you think the answer is and why (and something about how you go about working it), someone will be happy to help you. Otherwise, I think this will be a dry run for you.
Look up delta H in your text or notes. Delta H is negative for exothermic reactions.
To determine whether the reaction is exothermic or endothermic, we need to look at the sign of ∆H (enthalpy change).
In this reaction, the given enthalpy change is 452 kcal. Since kcal is a unit of energy, a positive value for ∆H indicates that energy is absorbed during the reaction, making it endothermic.
Therefore, the correct answer is:
B) endothermic; positive
To determine whether the given reaction is exothermic or endothermic, you need to determine the sign of the enthalpy change (ΔH). Here's how you can do that:
1. In the given reaction, the enthalpy values are given in kcal (kilocalories). However, to determine the sign of the enthalpy change, we need to compare the energy of the reactants to the energy of the products.
2. The reactants of the given reaction have a total energy of 452 kcal (kilocalories). In comparison, the products consist of solid phosphorus (P4) and gaseous chlorine (Cl2). Both solid and gaseous forms have lower energy compared to the reactants.
3. Since the total energy of the products is lower than the energy of the reactants, this indicates that energy has been released or given off during the reaction. In other words, the reaction is exothermic.
4. Therefore, the answer is: A) exothermic; neither positive nor negative.
Explanation: The given reaction is exothermic because it releases energy, as indicated by the fact that the enthalpy change (ΔH) is negative (since energy is being given off, the sign of ΔH is negative). However, from the options provided, there is no specific mention of the sign of ΔH, which means the answer is "neither positive nor negative."