3. a sample of octane (c3h18) gas has a mass of 1.135 g at a volume of 400. cm'3 and a temperature
of 200.°с. what is the pressure of the gas?

9.65 atm

Explanation:

From the question, we are given;

Mass of  octane is 1.135 gVolume of octane is 400 cm³ or 0.4 LTemperature of octane is 200°C

       But, K = °C + 273.15

Therefore, the temperature is equivalent to 473.15 K

We are required to calculate the pressure of the gas.

To do this, we are going to use the ideal gas equation;

According to the ideal gas equation;PV = nRT, where n is the number of moles, R is the ideal gas constant, 0.082057 L.atm/mol.KWe can rearrange the formula to calculate the pressure;

P = nRT ÷ V

But, n is the number of moles;Moles = Mass ÷ Molar massMolar mass of octane is 114.23 g/molMoles of octane = 1.135 g ÷ 114.23 g/mol

                                    = 0.00994 moles

Therefore;

P = 9.65 atm

Thus, the pressure of the gas is 9.65 atm