If the barometric pressure that day was 75.1 cm Hg, the temperature was 27.0°C and the volume in the pipette decreases from 51.0 mL to 42.0 mL, how many millimoles of gas (total) were removed from the initial air sample? (Enter as a decimal value, not in scientific notation and enter the value only. Note that a millimole is 10-3 mole.)

Respuesta :

Answer: 0.36 millimoles

Explanation:

According to ideal gas equation:

[tex]PV=nRT[/tex]

P = pressure of gas = 75.1 cm Hg = 0.98 atm    (1cmHg = 10 mm Hg)

V = Volume of gas = (51.0-42.0) ml = 9.00 ml = 0.009 L

n = number of moles = ?

R = gas constant = [tex]0.0821Latm/Kmol[/tex]

T = Temperature =[tex]27^0C=(27+273)K=300K[/tex]

[tex]n=\frac{PV}{RT}[/tex]

[tex]n=\frac{0.98atm\times 0.009}{0.0820 L atm/K mol\times 300K}=0.00036moles=0.36millimole\\ (1mole=1000millimol)[/tex]

Thus 0.36 millimoles were removed from initial air sample

The total number of mole of the gas that were removed from the initial sample is 0.36 millimole

From the question given above, the following data were obtained:

Pressure (P) = 75.1 cm Hg = 75.1 / 76 = 0.988 atm

Temperature (T) = 27 °C = 27 + 273 = 300 K

Volume (V) = 51 – 42 = 9 mL = 9 / 1000 = 0.009 L

Gas constant (R) = 0.0821 atm.L/Kmol

Number of mole (n) =?

Using the ideal gas equation (PV = nRT), we shall determine the total number of mole of the gas that were removed from the initial sample. This is illustrated below:

PV = nRT

0.988 × 0.009 = n × 0.0821 × 300

0.008892 = n × 24.63

Divide both side by 24.63

n = 0.008892 / 24.63

n = 0.00036 mole

Multiply by 1000 to express in millimole

n = 0.00036 × 1000

n = 0.36 millimole

Thus, the total number of mole of the gas that were removed from the initial sample is 0.36 millimole

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