± Electrolysis and Current The vapor pressure of water changes with temperature,
ID: 516243 • Letter: #
Question
± Electrolysis and Current
The vapor pressure of water changes with temperature, as shown here.
A student designs an ammeter (a device that measures electrical current) that is based on the electrolysis of water into hydrogen and oxygen gases. When electrical current of unknown magnitude is run through the device for 4.00 min , 16.9 mL of water-saturated H2(g) is collected. The temperature and pressure of the system are 25 C and 715 torr.
How many moles of hydrogen gas are produced?
Express your answer to three significant figures and include the appropriate units.
T (C) P (torr) 21 18.7 22 19.8 23 21.1 24 22.4 25 23.8 26 25.2 27 26.7 28 28.4 29 30.0 30 31.8Explanation / Answer
- 0.83v cathode reduction (negative)
4H2O(l) + 4e ---> 4OH(-) + 2H2(g)
while 4 electrons flow, 2 mole of H2 is liberated
- 0.40v anode oxidation (positive)
2H2O(l) ---> 4H(+) + 4e + O2(g)
while 4 electrons flow, 1 mole of O2 is liberated
- 1.23v overall reaction
2H2O(l) ---> 2H2(g) + O2(g)
use faraday equation for the calculation of H2 and O2 production
1st find out thr gas constant from wiki for pressure using torr and vol using Litter
R = 62.363 67 L-torr/K/mol
example: production of H2
V = olume of H2 produced in litter = 0.0169 L
P = pressure 715 torr
T = 25 + 273.15 = 298.15K
F = faraday constant 96485.3
e = number of electrons flow = 4
n = mol of H2 produced = 2
I = current in amperes
t = time in sec = 4 * 60 =240 sec
[ P * V ] = [ n * R * T ][ I * t ] / [ e * F ]
all the data seems available, you can use above equation to find the current ( I )
my excel calculation said
I = 0.261 amp = 261 mA
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.