A sample of gas contains (among other things): 7.0% CO, 15% CO2, 4.0% O2 and 4.5% CH4, all by volume. What is the mole fraction of methane in the sample?

How many moles of gas are contained in 890.0 mL at 21 °C and 100. kPa pressure? * 0.073 moles 510. moles 1.50 moles O 0.0364 moles

References Use the References to access important values if needed for this question. The stopcock connecting a 1.00 L bulb containing xenon gas at a pressure of 454 mm Hg, and a 1.00 L bulb containing nitrogen gas at a pressure of 526 mm Hg, is opened and the gases are allowed to mix. Assuming that the temperature remains constant, what is the final pressure in the system? mm Hg

A 1,365.8 mL aqueous solution of 407.9 mM Na2S is combined with 100.0 mL of an aqueous HCl solution whose HCl concentration is not known. The reaction produces 3.36 L of H2S gas at a pressure of 1.00 atm and a temperature of 11.88∘C. There is some Na2S remaining after the reaction is complete. What is the concentration of sulfide ions in the solution after the reaction has completed? Assume the volumes of the solutions are additive. Express your answer in units of millimolar (mM) using at least three significant digits.