The label has come off a cylinder gas in your laboratory. You know only that one species of gas is contained in the cylinder, but you do not know whether it is hydrogen, oxygen or nitrogen. To find out, you evacuate a 5-liter flask, seal it and weigh it, then let gas from the cylinder flow into it until the gauge pressure equals 1.00atm. The flask reweighed, and the mass of the added gas is found to be 13.00 g. Room temperature is 27oC, and barometric pressure is 1atm. What is the gas