2. A eudiometer contains 45 ml of oxygen when the barometer reading is 731.7 mm and the temperature is 27* C . The water level inside the tube is 68mm higher than that outside . What volume does the dry oxygen occupy at S.T.P?
To find the volume of dry oxygen at STP, we need to take into account the temperature, pressure, and the difference in water levels inside and outside the eudiometer.
1. Convert barometer reading to atm: Since the barometer reading is given in mm, we need to convert it to atm. The conversion factor is 1 atm = 760 mmHg. Therefore, 731.7 mmHg / 760 mmHg/atm = 0.962 atm.
2. Convert temperature to Kelvin: The temperature given in the problem is in degrees Celsius. To convert it to Kelvin, we add 273.15. Therefore, 27°C + 273.15 = 300.15 K.
3. Calculate the pressure inside the eudiometer: The pressure inside the eudiometer can be calculated by subtracting the difference in water levels inside and outside the eudiometer from the atmospheric pressure. In this case, the water level inside the eudiometer is 68 mm higher than outside. So, we subtract 68 mmHg * 1 atm/760 mmHg = 0.089 atm from the atmospheric pressure. Therefore, the pressure inside the eudiometer is 0.962 atm - 0.089 atm = 0.873 atm.
4. Apply the ideal gas law: In order to calculate the volume, we can use the ideal gas law equation: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.
Since we want to find the volume, we rearrange the equation as V = (nRT) / P.
5. Calculate the number of moles of oxygen: To find the number of moles of oxygen, we divide the given volume of oxygen by its molar volume at STP (22.4 L/mol). The volume of oxygen is given as 45 ml, which is equal to 0.045 L. Therefore, the number of moles of oxygen is 0.045 L / 22.4 L/mol = 0.0020089 mol.
6. Plug the values into the equation: Now we have all the necessary values to calculate the volume of dry oxygen at STP. Substitute the values into the equation:
V = (nRT) / P
V = (0.0020089 mol * 0.0821 L*atm/mol*K * 300.15 K) / 0.873 atm
7. Calculate the volume: By performing the calculation, we find that the volume of dry oxygen at STP is approximately 0.166 L.
Therefore, the volume of dry oxygen is 0.166 liters at STP.