Question

LAB 7. DETERMINING THE ATOMIC WEIGHT OF MAGNESIUM 2. A gas sample in a balloon contains 4.0 moles of gas at a particular pressure, volume and temperature. If your balloon springs a leak and the volume decreases to 1/2 of the original amount before you can plug the leak, how many moles of gas have you lost (temperature and pressure remain the same)?

Answer 1

(2) Initi al moles of gas, n = 4.0 moles initi al volume is V. final volume, V= - final moles, n = ? For constant pressure and temperature, the relation between moles of volume is un V. By Substitute the corresponding values in the above equation and calculate the final moles. ny = 4X4.0 moles 4.0 moles M = 2 ny = 2.0 moles loss of moles = m -n2 = 4.0 moles -2.0 moles = 2.0 moles Therefore, the required solution is 2.0 moles ----- ------ -------- -------- ------------------ (3) Given vapor pressure of water is 19 torr and the total pressure is 743 torr total pressure = Partial pressure of oxygen + vapor pressure of water Parti al pressure of oxygen = total pressure - vapor pressure of water Por = 743 torr – 19 torr = 724 torr Therefore, the parti al pressure of oxygen is 1724 torr ----------------------------------------------- Volume, V = 550 mL Temperature, T = 21 °C= 273+21 K = 294 K gas constant, R = 62.36367 L mmHg/mol. K Moles of oxygen, n= RT 724 torr x 550 mL 62.36367 L mm Hg/mol. KX294 K = 0.0216 mol 1mm Hg 1torr 1L 1000mL Therefore, the required solution is 10.0216 mol