20. The mass of a vessel filled with dry air is 97.432 g. Then, an unknown gas s

Question

20. The mass of a vessel filled with dry air is 97.432 g. Then, an unknown gas sample was injected into this vessel. The resulting mass of the vessel is 99.420 g. When this same vessel is filled with water, the resulting mass is 638.740 g. These measurements were done at 25 C and 758 Torr, at which the density of dry air and water are reported at 1.19 and 1000 g L-1, respectively. What is the molar mass of the unknown gas sample? A) 76.35 g mol-1 B) 89.98 g mol-1 C) 90.09 g mol-1 D) 450.0 g mol-1

Explanation / Answer

20) Volume of vessel(V) = m/d

                       = 638.74/1000

                       = 0.639 L

   mass of unknown sample(w) = 99.420-97.432 = 1.988 g

   R = 0.0821 l.atm.k-1.mol-1

   T = 25 c = 298 k

   P = 758 torr = 758/760 = 0.998 atm

from ideal gas equation

    PV = nRT

   PV = (W/M) RT

molarmass of unknown(M) = wRT/PV

                         = 1.988*0.0821*298/(0.998*0.639)

                          = 76.3 g/mol

answer: A) 76.35 g/mol

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

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