It has been a number of years since I studied general physics and I'm looking for help on how to solve the following question. This is not a homework question, this is me trying to satisfy my curiousity regarding an application at work. I have two 2L Erlenmeyer flasks, one flask (Flask A) contains 1.5L of water and has a stopper with two 1/4 ID tubes inserted into it. The first tube (Sample Tube) extends to a point near the surface of the water, but not below it and the top of this tube is sealed with a rubber septum. The second tube (Vent) extends all the way to a point near the bottom of the flask, well below the surface of the water and connects to the second stoppered flask (Flask B) which is empty. Again, in Flask B the Vent tube extends to a point near the bottom of the flask. A few grams of Calcium Carbide are added to Flask A and the stopper is replaced. The calcium carbide reacts with water to generate acetylene gas and as the volume of gas increases the water in Flask A is forced through the vent tube and into Flask B and the reaction continues until the water level in Flask A is is near the bottom of the vent tube but not below it. How would I go about determining the amount of pressure the acetylene gas in Flask A is under at a given point during this process? What is most important to me is to determine the amount of pressure required to begin moving the water up through the vent tube and into Flask B. Thanks for the help!