How do I calculate the partial pressure of HCl?

Calculate the percent by mass of aluminum in the sample.?

• A 42.0 mg sample of aluminum reacts with an excess of 6M HCl. A 42.6 Ml volume of hydrogen gas is collected over water at 20 degrees Celsius. The pressure of the "wet" hydrogen gas is adjusted to atmospheric pressure, a pressure of 750 Torr. Calculate the percent by mass of aluminum in the sample. The vapor pressure of water at 20 degrees Celsius is 17.5 Torr.

• Answer:

  Let UNITs guide you; always USE THEM in your calculation to prevent errors The pressure of the "wet" hydrogen gas is adjusted to atmospheric pressure, a pressure of 750 Torr. Atm is 760. No adjustment if vol remained the same! Firstly, the eqn: Al + 3HCl ----> 3/2H2 + AlCl3 moles H2 = PV/RT = [((750-17.5)torr/760torr/atm) * 0.0426 liters] / (0.08205 l-atm/moleK * (273+20)K) = ?? g Al = (2 moles Al/3 moles H2) * moles H2 * atwt Al g/mole Al = ?? % Al in sample = 100% * (g Al/g sample) = ?? Plug and SOLVE Basic mathematics is a prerequisite to chemistry – I just try to help you with the methodology of solving the problem.