5.15. The label has come off a cylinder of gas in your laboratory. You know only

Question

5.15. The label has come off a cylinder of gas in your laboratory. You know only that one species of gas is contained in the cylinder, but you do not know whether it is hydrogen, oxygen, or nitrogen. To find out, you evacuate a 5-liter flask, seal it and weigh it, then let gas from the cylinder flow into it until the gauge pressure equals 1.00 atm. The flask is reweighed, and the mass of the added gas is found to be 13.0 g. Room temperature is 27°C, and barometric pressure is 1.00 atm. What is the gas?

Explanation / Answer

Absolute pressure P = gauge + barometric

= 1 + 1

= 2 atm x 101325 Pa/atm = 202650 Pa

Volume of flask = 5 L x 1m3/1000L = 0.005 m3

Gas constant R = 8.314 J/mol·K

Temperature T = 27 + 273 = 300 K

From the ideal gas equation

Moles of gas n = PV/RT

= (202650 x 0.005 / (8.314 x 300)

= 0.4062 moles

Molar mass of gas = 13 g / 0.4062 moles

= 32 g/mol

We know that the molar mass of O2 = 32 g/mol

The gas is oxygen gas

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

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