Chemistry and Gas Concepts

Question

P1 is the pressure of Hydrogen gas with water vapor pressure removed using Dalton’s law of partial pressures.

What was P1?

Mg: 0.040 g

Room Temp: 294 K

Vapor Pressure of water: 18.7 mm Hg

Barometric Pressure: 1.001 atm

V1 (volume of experiment H2): 36.10 mL

Answer 1

Assuming that the Mg reacted with HCl to produce the H2 gas, we have

Mg + 2HCl ==> MgCl₂ + H₂(g)

Using the ideal gas law PV = nRT, we can solve for pressure (P)

P = pressure = ?

V = volume = 36.10 ml x 1 L/1000 ml = 0.03610 L

n = moles of gas = 0.04 g Mg x 1 mol Mg/24.3g x 1 mol H2/mol Mg = 0.00165 moles H2

R = gas constant = 0.0821 Latm/Kmol

T = temperature in Kelvin = 294

Solving for P we have: P = nRT/V

P = (0.00165)(0.0821)(294)/0.03610

P = 1.10 atm = total pressure

pressure of water (water vapor) = 18.7 mm Hg x 1 atm/760 mm Hg = 0.025 atm

P1 = pressure of H2 with water vapor removed = 1.10 atm - 0.025 atm = 1.075 atm