Question

Molar Volume of a Gas lab: How do I determine the volume of hydrogen collected at STP and SATP, and the molar volume at STP and SATP?

Answer 1

Room temperature (°C) 22.0
Barometric pressure (kPa) 100.5
Water vapor pressure at 22 °C (kPa) 2.60
Mass of Mg ribbon (g) 0.0500
Volume of hydrogen gas (mL) 48.3

Observations of reaction
• when the Mg came into contact with the HCl bubbles of gas (H2) were produced
• the H2 produced displaced the water in the graduated cylinder

Answer 2

oh here:

2HCl(g) + Mg(s) -> H2(g) + MgCl2(aq)

nMg = 0.0020571899 mol
nH2 = 0.0020571899 mol

Wet H2 pressure = 100.5 kPa
Dry H2 pressure = 97.9 kPa

--- Vstp = 22.4 L/mol, and Vsatp = 24.8 L/mol
Vstp:0 degrees Celsius and 101.325 kPa while Vsatp: 25 degrees Celsius and 100 kPa.

100.5 kPa x 760 mm Hg/101.325 kP = 753.8119911 mmHg

So to determine the volume of hydrogen gas collected at STP:

V2 = (753.8119911 mmHg)(48.3 mL)(273 K) / (295 K)(760 mmHg)
= 44.33403003 mL

Molar volume at STP:

mol/L = 44.33403003 mL / 0.0020571899 mol
= 21550.77176 mL/mol
= 21.55077176 L/mol

To determine volume of hydrogen gas collected at SATP:

V2 = (100.5 kPa)(48.3 mL)(298 K) / (295K)(100kPa)
= 49.03514237 mL

Molar volume at SATP:

mol/L = 49.03514237 mL / 0.0020571899 mol
= 23835.98246 mL/mol
= 23.8359824 L/mol

Are my answers correct? :$

Answer 3

You have the work out with:
Volume of H2 (STP) :
V' = ( 48.3 ml * 97 .9 * 273 ) / 100.5 * 295 = 43.54 mL
Mole of H2 = .0434 ml / .0021 = 21.17 mol

Answer 4

so wait only the volume of H2 (ST) is wrong?

Answer 5

The key is you need to use corrected Pressure 97 .9 kPa, because we want the dry H2 gas!

Answer 6

ohh didn't I use it?

Answer 7

ohhh.. i don't use the wet one?

Answer 8

V2 = (753.8 mmHg)(48.3 mL)(273 K) / (295 K)(760 mmHg) = 44.33 mL
I doesn't look like you use the dry one !!!

Answer 9

so basically I replace the 100.5 kPa from both of the calculations STP and SATP to 97.9 kPa?

Answer 10

lol, thank you!

Answer 11

ohh it's 20993.23937.. o.O

Answer 12

The 20.73 mol is the correct one.

Answer 13

wait I am so confused now D:

Answer 14

this part: Mole of H2 = .0435 L / .0021 = 20.73 mol

Answer 15

ohhh i see it. Never mind, thanks again!

Answer 16

Volume of H2 (STP) :
V' = ( 48.3 ml * 97 .9 * 273 ) / 101.3 * 295 = 43.197 mL
Molar Volume of H2 = .043197 ml / .0021 = 20.99 mol