Answer to Question #66737 in General Chemistry for Yesenia Gonzalez

Question

1.A certain gas expands from 5.768L to 9.876L at constant temperature.Calculate the work done in Joules by the gas if it expands against a constant pressure of 4.3 atm.

2.what volume of 0.050M H3PO4 solution is needed to neutralize 50mL of 0.350M KOH

3. Hydrogen gas expands from a volume of 7.65L to 10.36L under a constant pressure of 2.31atm while releasing 215Joules of heat.What is the change in energy of the system?

Answer 1

1. A certain gas expands from 5.768L to 9.876L at constant temperature.Calculate the work done in Joules by the gas if it expands against a constant pressure of 4.3 atm.
Solution:
Working gas expanding
W = PdV
W= 405300 Pa x (0,009876 m^3 - 0,005768 m^3) = 1664.9724 J
Answer: 1664.9724 J

2. What volume of 0.050M H3PO4 solution is needed to neutralize 50mL of 0.350M KOH
Solution:
C1V1 = C2V2
V1 = C2V2/ C1
V1 = 50mL x 0.350M / 0.050M = 350 ml H3PO4
Answer: 350 ml H3PO4

3. Hydrogen gas expands from a volume of 7.65L to 10.36L under a constant pressure of 2.31atm while releasing 215Joules of heat.What is the change in energy of the system?
Solution:
Working gas expanding
W = PdV
We use of the first principle of thermodynamics
Q = U + W
U = Q - W
U = Q - PdV
U = 215 J - 234060,8 Pa x (0,01036 m^3- 0,00765 m^3) = - 419 J
The change in energy of the system is negative, this means that it is emitted into the environment
Answer: - 419 J