A) A sample of oxygen gas collected at STP occupies a volume of 35.6 L. How many

Question

A)

A sample of oxygen gas collected at STP occupies a volume of 35.6 L. How many moles of gas does the sample contain?

_________mol

C)A mixture of oxygen and carbon dioxide gases, in a 9.66 L flask at 60 °C, contains 5.34 grams of oxygen and 15.8 grams of carbon dioxide. The partial pressure of carbon dioxide in the flask is ___________ atm and the total pressure in the flask is _____________ atm.

STP (standard temperature and pressure) is used as a reference point for the molar volume of an ideal gas. In the USA, most chemists, most general chemistry texts, and OWL use STP = 0°C, 1 atm, where the molar volume = 22.4 L/mol. If the reference pressure is chosen to be 1 bar, the molar volume is 22.7 L/mol. Do not confuse the two.

Explanation / Answer

A) At STP, 1 mole of gas occupies volume of 22.4 L.
number of moles of gases which occupies volume of 35.6 L = 35.6/22.4 = 1.59

B) C4H10 (g) + (13/2)O2(g) --> 4CO2(g) + 5H2O(g)

As P & T are constants, V is directly proportional to n.
1 mole of C4H10 react with oxygen to give 9 moles of gaseous products.
so, final volume = (initial volume of C4H10)* 9 = 9 * 26.2 L = 235.8 L

C) number of moles of carbon dioxide = 15.8/44 = 0.3591
number of moles of oxygen = 5.34/32 = 0.1689

PCO2 = nCO2RT/V = 0.3591*0.0821*333.15/9.66 atm = 1.02 atm
Ptotal = ntotalRT/V = (0.3591+0.1689) * 0.0821 * 333.15 / 9.66 =1.49 atm

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