Calculate the density of oxygen, O2, under each of the following conditions: STP
ID: 809907 • Letter: C
Question
Calculate the density of oxygen, O2, under each of the following conditions: STP 1.00 atm and 10.0 ?C Express your answers numerically in grams per liter. Enter the density at STP first and separate your answers by a comma. To identify a diatomic gas (X2), a researcher carried out the following experiment: She weighed an empty 4.1-L bulb, then filled it with the gas at 1.50atm and 20.0 ?C and weighed it again. The difference in mass was 7.1g . Identify the gas. Express your answer as a chemical formula.
Explanation / Answer
a) molar mass O2 = 32 g/mol
d = 32 x 1 atm / 0.08206 x 273 =1.43 g/L ( at STP)
d = 32 x 1 / 0.08206 x 283 K= 1.377 g/L ...........answer
b)
number of moles of gas in the flask = PV / RT
= 1.5atm x 4.1L / 0.082 L atm K?1 mol?1 x (20+273)K
= 0.255 moles which has mass of 4.7 g so 1 mole of gas has mass of
7.1 / 0.255 = 27.84 g / mole or almost 28 g/mole
So , the gas is nitrogen ..