Answered Essay: Simplify the energy balance equation for eavch of the following cases. State
Simplify the energy balance equation for eavch of the following cases. State whether Q or W is positive, negative or zero in each case. Clearly state your choice of system. a. Water in a lake falls 200 meters through a 6 inch diameter pipe and exits into a river System = ____________ b. Acetic acid flows through tubes of a furance, where it reacts to ketene and water. System =______ c. Cold milk is added to a hot cup of coffee. System = Also, I need to Know in EACH CASE please the following 1-if (delta potential energy) and/or (delta Kinetic energy) is zero or not ? 2-if the system is (open system) or (closed system)? would truly appreciate If someone can explain since I’m confused also when to use (delta U) and (delta H) ?
Expert Answer
a) W = positive and Q = negative
Explanation: When water flows from the lake into a river, the work is done on the system, i.e. W = positive.
W and Q will have opposite signs, i.e. Q = negative.
b) W = negative and Q = positive
Explanation: When acetic acid flows through a furnace and reacts to ketene and water, the work is done by the system, i.e. W = negative.
c) W = positive and Q = negative
Explanation: When hot milk is added to cold coffee, the heat releases, i.e. Q = negative.
1. a) ∆(KE) ≠ 0 (i.e. positive due to the flow/motion of water) and ∆(PE) = 0 (due to no change in the state of water)
b) ∆(KE) ≠ 0 (i.e. positive due to the flow/motion of acetic acid) and ∆(PE) ≠ 0 (i.e. negative, at the expense of PE, KE increases)
c) ∆(KE) = 0 (i.e. due to no flow/motion of coffee) and ∆(PE) ≠ 0 (i.e. positive, due to the change in the state of coffee)
2. a) Open system
b) Closed system (because the reaction occurs in the furnace)
c) Open system
∆U = The change in potential energy and ∆H = The change in enthalpy or total heat content of the syste.
