Calculate the density of oxygen, O_2, under each of the following conditions: ST

Question

Calculate the density of oxygen, O_2, under each of the following conditions: STP 1.00 atm and 35.0 degree C Express your answers numerically in grams per liter. Enter the density at STP first and separate your answers by a comma. density at STP, density at 1 atm and 35.0 degree C = To identify a diatomic gas (X_2), a researcher carried out the following experiment: She weighed an empty 4.7-L bulb, then filled it with the gas at 1.80 atm and 30.0 degree C and weighed it again. The difference in mass was 9.5 g. Identify the gas. Express your answer as a chemical formula.

Explanation / Answer

A)

p*V=n*R*T

p*V=(mass/molar mass)*R*T

p*molar mass=(mass/V)*R*T

p*molar mass=density*R*T

i) at STP

p*molar mass=density*R*T

1 atm * 32 g/mol = density * 0.0821 atm.L/mol.K * 273 K

density = 1.43 g/L

ii)

T = 35.0 oC = (35 + 273) K = 308 K

p*molar mass=density*R*T

1 atm * 32 g/mol = density * 0.0821 atm.L/mol.K * 308 K

density = 1.27 g/L

Answer: 1.43, 1.27 g/L

B)

1st calculate the number of mol of gas filled.

P = 1.80 atm

V = 4.7 L

T = 30.0 oC = (30.0+273) K

= 303 K

use:

P * V = n*R*T

1.80 atm * 4.7 L = n * 0.0821 atm.L/mol.K * 303.0 K

n = 0.3401 mol

now use:

n = mass / molar mass

0.3401 mol = 9.5/mm

mm = 28 g/mol

molar mass of N2 is 28 g/mol

So, it is N2

Answer: N2

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