1. The problem statement, all variables and given/known data A quantity of 4.50 g CaC2 is reacted with an excess of water at 298K and atmospheric pressure. CaC2 (s) + 2 H2O (l) --> Ca(OH)2 (aq) + C2H2 (g) Calculate the work done in Joules by the Acetylene gas against the atmospheric pressure. 2. Relevant equations After asking my PChem professor, he said the I should use the work formula for an isothermic gas expansion, w= -nRT ln(V2/V1) also for an isothermic expansion, q=-w 3. The attempt at a solution P= 1 atm, n= 0.0702 mol R= 8.314 J/mol*K I easily found the mole of the gas (0.0702), but my biggest problem is what are the volumes that are supposed to be used here? Using the moles of an ideal gas (22.4 L/mol), I found that the volume of the acetylene gas is 1.572 L, but I don't have a second volume to complete the equation. I feel like I'm missing something important, but I can't figure it out.