Water electrolysis, work done, and volume change

In summary: Q=c x m x ΔTIn summary, the temperature of the system increases, and the volume of the system changes.
  • #1
HelloCthulhu
151
3
I'm trying to learn more about water electrolysis and the work done on and by the system, but I'm still very confused about a few elements. Knowing the volume of the closed container, the number of moles of water, the amps/volts from the battery, and the initial temperature of the water, I know I can calculate the final temperature of the system using the specific heat capacity formula:

Q=c x m x ΔT

I can also use Faraday's law of electrolysis to solve for gas produced. Assuming the external pressure is standard in a closed system, how can I calculate the change in volume as the gas expands?
 
Chemistry news on Phys.org
  • #2
HelloCthulhu said:
Knowing the volume of the closed container

HelloCthulhu said:
the external pressure is standard in a closed system

So what is kept constant - pressure, or volume?
 
  • #3
Borek said:
So what is kept constant - pressure, or volume?

The external pressure is constant. Using the ideal gas law, does this mean I can just divide nRT by standard P now?

Actually, I'm very confused. If the temperature increases inside of the container, won't the pressure inside of the container increase too?
 
Last edited:
  • #4
HelloCthulhu said:
The external pressure is constant. Using the ideal gas law, does this mean I can just divide nRT by standard P now?

So the volume of the container changes,. No problem, you just need to be precise.

Actually, I'm very confused. If the temperature increases inside of the container, won't the pressure inside of the container increase too?

If the pressure is equilibrated with the outside pressure, then no.
 
  • #5
Let's say 2 moles of water at 20°C undergoes electrolysis at 5A/40V inside of a closed 40mL container for 1 min at standard external/internal pressure. I'll calculate the total temperature of the system first.

Gas Produced
(5A*60s*4g)/(F*4)=0.00311g H2
(5A*60s*32g)/(F*4)=0.024875g O2
0.00311g + 0.024875g = 0.02798g

Temperature of the system
Q=cmΔT
5A*40V*60s=12kJ
Liquid 36g x 4.18J/(g⋅K)=150.48J/(g⋅K)
Gas 0.02798g x 2.080J/(g⋅K)=0.0582J/(g⋅K)
150.48J/(g⋅K) + 0.0582J/(g⋅K)=150.538J/(g⋅K)
12kJ=150.538J/(g⋅K)/(g⋅K)*ΔT
12kJ/150.538J/(g⋅K)=(T2-20°C)
79.7 + 20°C=99.7°C

Does the rise in temperature cause the total volume of the system to increase? If so, how do I calculate the change in volume? I think I'm supposed to use the volume of the container as initial volume and use Charle's law to calculate the change but I'm not sure in this case.

Vi/Ti = Vf/Tf

0.040L/293K=Vf/372.85
Vf=0.05L
 

1. What is water electrolysis?

Water electrolysis is a process in which an electric current is passed through water, breaking it down into its component elements of hydrogen and oxygen gas. This is achieved by using two electrodes, one connected to the positive terminal of a power source and the other to the negative terminal, and placing them in the water. This causes a chemical reaction that separates the water molecules into their individual elements.

2. How does water electrolysis work?

In water electrolysis, an electric current is used to split water molecules into hydrogen and oxygen gas through a process called oxidation-reduction reactions. The positive electrode (anode) attracts the negatively charged oxygen ions, while the negative electrode (cathode) attracts the positively charged hydrogen ions. This results in the production of hydrogen gas at the cathode and oxygen gas at the anode.

3. What is the work done in water electrolysis?

The work done in water electrolysis is the amount of energy required to separate the water molecules into hydrogen and oxygen gas. This energy is provided by the electric current, and the amount of work done is directly proportional to the amount of electricity used. The standard unit for work is joules (J).

4. How does water electrolysis affect volume?

In water electrolysis, the volume of the gas produced is directly proportional to the amount of electricity used. This means that as more electricity is passed through the water, the volume of gas produced will increase. This is because the electric current causes the water molecules to break down into their component gases, resulting in an increase in volume.

5. What are the practical applications of water electrolysis?

Water electrolysis has various practical applications, such as in the production of hydrogen gas for fuel cells, the production of oxygen for medical and industrial purposes, and in the purification of water. It is also used in the production of certain chemicals and in the metallurgy industry. Additionally, water electrolysis can be used to store excess renewable energy in the form of hydrogen gas, which can then be used as a clean and sustainable energy source.

Similar threads

Electrolysis of Water -- Rate of Reaction?
    • Chemistry
Replies
8
Views
2K
Potassium Chloride Electrolysis
    • Chemistry
Replies
5
Views
1K
Concentration of electrolyte for the electrolysis of water?
    • Chemistry
Replies
7
Views
2K
Why is this water turning black during electrolysis?
    • Chemistry
Replies
19
Views
9K
Temperature of gas during water electrolysis
    • Chemistry
Replies
21
Views
3K
Electrolysis to reduce water's saltiness?
    • Chemistry
Replies
4
Views
1K
Isolating CO2 in the electrolysis of Na2CO3 solution
    • Chemistry
Replies
7
Views
4K
Does mixing glycerol into water effect electrolysis of water?
    • Chemistry
Replies
14
Views
9K
Chemistry Amount of water electrolyzed during PEM electrolysis
    • Biology and Chemistry Homework Help
Replies
26
Views
3K
Magnetic Field and Water Electrolysis Work
    • Chemistry
Replies
4
Views
3K

Hot Threads

Recent Insights

Back
Top