ChemB unit 3 custom test:
1.)Is this question endothermic or exothermic
PCI3 (s)+CI2 (g)—> PCI5 (s) + energy
2.) Is this question endothermic or exothermic?
2KNO3 (S) + energy —>2KNO2 (s) +O2
3.) When new chemical bonds form,energy______.
Is taken into the system
Stays the same in the system
Is released from the system
4.)Does breaking bonds require energy,release energy, or not involve energy at all?
Requires energy to be absorbed into the system
No energy is involved
Releases energy when broken
5.) When solids Ba(OH)2 and NH4SCN are mixed, a solution is produced and the temperature drops. Which statement about energetics of this reaction is correct?
The reaction is endothermic and H is negative
The reaction is exothermic and H is negative
The reaction is another make an age is positive
Reaction is exothermic and H is positive
Please help, I am stuck!!
1. Exothermic
2. Endothermic
3. Is released from the system
4. Requires energy to be absorbed into the system
5. The reaction is endothermic and H is negative
oops! 5 is not answered correctly. If the solution gets colder then endothermic is right BUT when a reaction is endothermic then delta H is positive. Actually the correct answer is not listed; however, I expect answer C, which is nonsense as posted, was correct and was not typed in correctly.
To determine whether a chemical reaction is endothermic or exothermic, you need to consider the enthalpy change (ΔH) of the reaction.
1.) In the first question, you are given the reaction: PCI3 (s) + CI2 (g) -> PCI5 (s) + energy. The presence of "energy" on the product side indicates that heat is released during the reaction. Thus, the reaction is exothermic.
2.) In the second question, you are given the reaction: 2KNO3 (S) + energy -> 2KNO2 (s) + O2. Since "energy" is on the reactant side, it means that heat is being absorbed during the reaction. Thus, the reaction is endothermic.
3.) When new chemical bonds form, energy is released from the system. Therefore, the correct statement is "Is released from the system."
4.) Breaking bonds requires energy to be absorbed into the system. Therefore, the correct statement is "Requires energy to be absorbed into the system."
5.) When solids Ba(OH)2 and NH4SCN are mixed, and the temperature drops, it implies that energy is being released from the system. Therefore, the correct statement is "The reaction is exothermic and H is negative."
Remember to pay attention to the terms "energy" in the reactants or products, as well as the overall change in temperature to determine whether a reaction is endothermic or exothermic.