1. The molar volume of H2 gas at STP is 22.433 L/mol. We want to verify this num
ID: 1050901 • Letter: 1
Question
1. The molar volume of H2 gas at STP is 22.433 L/mol. We want to verify this number in this experiment by reacting a strong acid with a metal to produce hydrogen gas. The following reaction takes place in a eudiometer tube: 2H.aq) + Mg(s) Mg2.(aq) + H2(g) A 0.0302 g sample of elemental magnesium is reacted with an abundant amount of hydrochloric acid. The volume of hydrogen gas collected over water is 33.44 mL The temperature of the water is 23.2 °C. (Refer to Table 9.1 for water vapor pressure values.) The atmospheric pressure recorded in lab is 748.2 torr. The pressure difference between the two menisci is 460.0 mm H20. Calculate the following values in the unit required by the relevant formulas and show all your work. Calculation Molar mass of Mg = (1 point) Atmospheric pressure in mm Hg (1 point) Water vapor pressure in mm Hg = (1 point) Pressure difference in mm Hg = (1 point) 241Explanation / Answer
Molar Mass of Mg = 24.305
Atmospheric pressure = 748.2 torr = 748.2 mmHg
Water Vapour Pressure =20.82 mmHg
Pressure Difference = 748.2-20.82 = 727.38 mm Hg
1 mm Hg= 13.54831 mm H2O
460 mm H20 = 33.9525 mm Hg
33.9525 mm Hg = pressure of H2 Gas = 0.04467 atm.
Water Bath Temperature in K = 273.15+23.2 = 296.35 K
Eudiometer volume of H2 Gas = 33.44 mL = 0.03344 L
P1V1/T1 = P2V2/T2
748.2 atm* 0.03344 L/296.35 K = 1 atm * V2/273.15 K
V2= 0.03032 L
1 mole = 22.433 L
0.03032 L is 1.3519*10^-3 moles
Moles of Mg = 1.3519*10^-3 moles
theoritical moles of Mg = 0.0302/24.305=1.24254*10^-3 moles
%error = (experimental value- theoretical value )*100/Theoretical value = 8.8%
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