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In one experiment, 0.780 g Nb (s) was sealed in a 28.0 mL glass tube at 25°C
under 6.33 atm of hydrogen gas, H2. After reacting with the hydrogen for one
week, all of the niobium had been converted to niobium hydride, NbH. Calculate
the final pressure of hydrogen gas in the system at 25°C.
Balanced equation:
2Nb +H2 ? 2NbH
2mol Nb react with 1mol H2 to produce 2 mol NbH
Molar mass Nb = 92.9064 g/mol
0.78g Nb = 0.78/92.9064 = 8.4*10^-3 mol Nb
This will react with 4.2*10^-3 mol H2
Mol of H2 started with:
PV = nRT
6.33*0.028 = n*0.082057*298
n = 7.25*10^-3 mol
Mol of H2 unreacted = 7.25*10^-3 – 4.2*10^-3 = 3.048*10^-3 mol H2
You finally have 3.048*10^-3 mol H2 in 28ml container at 25°C
Calcualte pressure by gas law equation:
PV = nRT
P * 0.028 = (3.048*10^-3) * 0.082057 * 298
P = 2.66 atm
This question seems a litle tricky since they are not giving you the final temperature or the final volume. So we’re gonna asume that the temperature and volume remain constant.
For this question you re gonna use the formula:
P1V1/T1 = P2V2/T2
P = pressure in atm
V = Volume in Liters
T = Temperature in Kelvin,
So they are giving the volume in mL so you must change it to liters.
28.0mL * 1L / 1000mL = 0.028 L
And the temperature is i celsius so add 273 to get it in Kelvin.
25 + 273 = 298 K
Then you move around the formula so you are solving for P2, All the 2 values are the final values.
So you would have:
P2 = P1V1T2 / T1V2 And now we just plug in.
(6.33 atm ) (0.028L)(298K) / (298K)(0.028L) = 6.33 atm
So the pressure would be the same,
Hope that helps!!!!
67 psi
![p389sml[1]](http://farm4.staticflickr.com/3119/2665437479_e1a40381b8_t.jpg)
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