Hydrogen gas is collected over water at 25 degree C and an atmospheric pressure

Question

Hydrogen gas is collected over water at 25 degree C and an atmospheric pressure of 766 mm Hg. Refer to Table 16.1 and show the calculation pressure of hydrogen gas. A 0.0795-g sample of magnesium metal reacts with hydrochloric acid to give 88.5 mL of hydrogen gas at 25 degree C and 766 mm Hg. Refer to Example Exercise 16.1 and show the calculation for the volume of hydrogen gas at STP. Calculate the moles of hydrogen gas produced. Calculate the molar volume of hydrogen gas at STP. What are major sources of experimental error?

Explanation / Answer

(6)

Partial pressur eof H2 gas = total pressure - aqueous tension at 250C

= 766 - 23.8

= 742.2 mm Hg

(7)

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

Mass of Mg = 0.0795 g.

Molar mass of Mg = 24 g/mol

Number fo moles of Mg = 0.0795 / 24 = 0.00331 mol

According to the above balanced eqaution,

1 mol Mg can produce 1 mol H2

Then, 0.00331 mol Mg can produce 0.00331 mol H2

Given that, Pressure of H2, P1 = 766 mm Hg = 766 / 760 atm = 1.008 atm

Volume of H2 gas, V1 = 88.5 mL = 0.0885 L

Temperature, T1 = 25 + 273.15 = 298.15 K

At STP,

P2 = 1 atm

T2 = 273.15 K

V2 = ?

P1V1/T1 = P2V2/T2

1.008 * 0.0885 / 298.15 = 1 * V2 / 273.15

V2 = 0.0817 L

Then, molar volume at STP = 0.0817 / 0.00331 = 24.7 L

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.