Which you can be measured how much is something we have so we can say that the amount gas in this tank is I'm 7.5 mol now whenever we have a sample gas like this numbers tanker it's in a balloon or wherever is we can describe we can get these various characteristics and it turns out that also for any sample gas if we know and these characteristics we can figure out weather for is all we need to do is on three in order do that we use an equation as a representation that ideal gas law and it's written is PคูณV = nคูณRคูณT on Get two are in a sec don't worry about it for right now it's be a number that we know.