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What is the molar mass of an unknown gas if a sample weighing 0.389 g is collected in a flask with a volume of 102 cm³ at 97°C and at a pressure of 728 mmHg? (R = 0.08206 L • atm/K • mol, 1 atm = 760 mmHg).



Answer :

Despina

Answer:

To calculate the molar mass of an unknown gas, we can use the formula:

Molar mass = Given Mass/Number of moles

First let's calculate the number of moles which can be calculated using the ideal gas law:

PV = nRT

where,

  • P is pressure ( in atm)
  • V is volume (in l)
  • n is Number of moles
  • R is universal gas constant 0.08206 L atm/Kmol
  • T is temperature (in Kelvins)

Given that if a sample weighing 0.389 g is collected in a flask with a volume of 102 cm³ at 97°C and at a pressure of 728 mmHg

Converting the values,

Volume = 102 cm³ = 0.1 L

Temperature = 97°C = 97°C + 273.15 = 370.15 K

Pressure = 728 mm Hg = 728 mmHg / 760 mmHg/at = 0.958 atm

Calculate (n) number of moles:

0.958* 0.1 = n* 0.0821*370.15

0.0958 = n (30.39)

Divide both sides by 30.39

n = 0.031

Now, calculate the molar mass:

Molar mass = 0.389/0.031

Molar mass = 12.54 g/mol

So, the molar mass of the unknown gas is approximately 12.54 g/mol.

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