If a current of 2.5A flows for 2hrs
45mins through a water voltameter.
Determine the volume of
hydrogen gas at s.t.p. [molar volume
of gasesat s.t.p = 22.4dm3.?
The correct answer is 2.87 L.
2.75 x 60 x 60 x 2.5 = 24,750
96,485 C will release 22.4/2 = 11.2 L H2 @ stp.
11.2 L x (24,750/96,485) = 2.87 L H2 @ stp.
seconds = 2 (3600) + 45 * 60 = 9900 seconds
coulombs = current * time = 2.5 * 9900 = 24750 Coulombs
How many electrons?
24750 Coulombs ( 1 electron / 1.6*10^-19 coulombs)
= (2.475 /1.6) 10^23 electrons
Each H+ needs one electron so each H2 molecule needs two
do we get 7.73 * 10^22 H2 molecules
How many mols is that?
6 * 10^23 molecules/mol
so
7.73*10^22 molecules ( 1 mol / 6*10^23 molecules) = 0.129 mol
0.129 mol * 22.4 liter/mol = 2.9 liters
an A (ampere) is a Coulomb of charge per second
... there are 9.5E4 Coulombs in a mole of electrons
each mole of H2 requires two moles of electrons
moles elec = 2.5 * 2.75 * 60 * 60 / 9.5E4
calculate moles elec , divide by two for moles of H2
So, sorry. I didn't pay ful l attention. It's H2 so 1 atom contains 2 electrons. So, 1 mole of a H2 gas at STP will contain 2 moles of electrons.
2.75Hr*(60min/Hr)*(60s/min)=9,900s
C=charge=current*time(s)=2.5A*9,900s=24750 C
Faraday's constant=9500 C=1 mole
24750*(mole/9500)=0.25648moles
*****Correction
1 mole= 2 moles of e^-=22.4L at STP
0.25648 moles of e^-*(22.4L/2 moles of e^-)=2.87=2.9L
All of the calculations that gave you 2.9L are correct.
2.75Hr*(60min/Hr)*(60s/min)=9,900s
C=charge=current*time(s)=2.5A*9,900s=24750 C
Faraday's constant=9500 C=1 mole
24750*(mole/9500)=0.25648moles
1 mole=22.4L at STP
0.25648*22.4=5.74L
Check arithmetic. I did that fast.
but Anon you need 2 mols of electrons for one mol of H2
To determine the volume of hydrogen gas at standard temperature and pressure (s.t.p), we need to use the formula:
Volume of gas (V) = Current (I) × Time (t) × Constant (C)
Where:
- Current (I) is given as 2.5A.
- Time (t) is given as 2 hours and 45 minutes, which can be converted to decimal hours. 45 minutes is equal to 0.75 hours, so the total time is 2 + 0.75 = 2.75 hours.
- Constant (C) represents the molar volume of gases at s.t.p, which is given as 22.4 dm^3.
Now, we can substitute these values into the formula to find the volume of hydrogen gas:
V = 2.5A × 2.75 hours × 22.4 dm^3
First, multiply the current and time:
V = 6.875A hours × 22.4 dm^3
Next, multiply the result by the constant:
V = 153.5 dm^3
Therefore, the volume of hydrogen gas at standard temperature and pressure is 153.5 dm^3.