Match the reaction conditions (all at constant pressure) with the statements abo
ID: 484631 • Letter: M
Question
Match the reaction conditions (all at constant pressure) with the statements about enthalpy that are true for those conditions.
Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a battery and used to power a flashlight.
Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a battery and used to power a flashlight.
Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a beaker and allowed to react on their own.
Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a beaker and allowed to react on their own.
The change in enthalpy does NOT equal the change in internal energy, but the change in enthalpy DOES equal the heat gained or lost (q).
The change in enthalpy does NOT equal the change in internal energy, and the change in enthalpy does NOT equal the heat gained or lost (q).
The change in enthalpy DOES equal the change in internal energy, and the change in enthalpy DOES equal the heat gained or lost (q).
The change in enthalpy DOES equal the change in internal energy, but the change in enthalpy does NOT equal the heat gained or lost (q).
- A. B. C. D.Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a battery and used to power a flashlight.
- A. B. C. D.Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a battery and used to power a flashlight.
- A. B. C. D.Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a beaker and allowed to react on their own.
- A. B. C. D.Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a beaker and allowed to react on their own.
A.The change in enthalpy does NOT equal the change in internal energy, but the change in enthalpy DOES equal the heat gained or lost (q).
B.The change in enthalpy does NOT equal the change in internal energy, and the change in enthalpy does NOT equal the heat gained or lost (q).
C.The change in enthalpy DOES equal the change in internal energy, and the change in enthalpy DOES equal the heat gained or lost (q).
D.The change in enthalpy DOES equal the change in internal energy, but the change in enthalpy does NOT equal the heat gained or lost (q).
Explanation / Answer
Note... if there is volume formation, then;
dH = dU + d(PV) will differ
only when dV --> 0, we can assume
dH= dU
so these cases, in which enthalpy = internal energy --> between Zn(s) + Cu2+ ... since there is no H2(g) production
so for the other cases, in which enthalpy is NOT internal energy --> Choose H2(g) production!
If they are used to react by their own, then... the enthalpy = heat/gain lost
If they are use to light a flashlight, enthalpy = some heat + some light, so...
1)
Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a battery and used to power a flashlight. --> Choose (D) The change in enthalpy DOES equal the change in internal energy, but the change in enthalpy does NOT equal the heat gained or lost (q).
2)
Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a battery and used to power a flashlight. (B) The change in enthalpy does NOT equal the change in internal energy, and the change in enthalpy does NOT equal the heat gained or lost (q).
3)Zn (s) + Cu2+ (aq) --> Zn2+ (aq) + Cu (s) where the reactants are placed into a beaker and allowed to react on their own. (C) The change in enthalpy DOES equal the change in internal energy, and the change in enthalpy DOES equal the heat gained or lost (q).
4)
Zn (s) + 2H+ (aq) --> Zn2+ (aq) + H2 (g) where the reactants are placed into a beaker and allowed to react on their own. (B) The change in enthalpy does NOT equal the change in internal energy, and the change in enthalpy does NOT equal the heat gained or lost (q).