Aperfect gas is contained in a cylinder of fixed volume and which is separated into two sections a and b by a frictionless piston; no heat can pass through the piston. b is maintained at a constant temperature of 300 k; that is, all changes in section b are isothermal. there are 2.00 mol of gas molecules in each section and the constant-volume heat capacity of the gas is cvm=20 j k−1 mol−1, which can be assumed to be constant. initially ta=tb=300 k, va=vb=200 dm3. energy is then supplied as heat to section a so that the gas in a expands, pushing the piston out and thereby compressing the gas in section b. the expansion takes place reversibly and the final volume in section b is 1.00 dm3. because the piston is free to move, the pressures in sections a and b are always equal, recall, too, that for a perfect gas the internal energy is a function of only the temperature. (a) calculate the final pressure of the gas and hence the temperature of the gas in section a. (b) calculate the change in entropy of the gas in section a.

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While studying chemical reactions and conservation of matter, sarah's class conducted a variety of experiments. sarah and her lab partner found the mass of a wax candle and placed the candle in a flask. the students lit the candle and let it burn to completion. all that was left was wax and charred candle wick. per their teacher's instructions, the students found the mass of the products. their data can be seen in the data table. formulate a hypothesis the students could test to explain why the experiment did not support the law of conservation of matter. a) the students could repeat the experiment using different candles; there might have been a flaw in the candle. b) the experiment should be repeatable. the students should run several trials and then take an average of the after mass in each trial. c) the students should have someone in the class check their measurement skills as they repeat the experiment. they may have made an error using the balance. d) the students should burn the candle in a container that has some type of lid so that any gas that is a product of the reaction can be contained and massed. submit

Select all the correct answers. which changes will increase the rate of reaction during combustion? decreasing the area of contact between the reactants adding more oxygen to the reaction removing heat from the reaction changing the reactants from solid form to powdered form lowering the exposure of the reactants to air