In an experiment ,dry hydrogen gas was passed over hot copper (II) oxide in a combustion tube as shown in the diagram below ​

by upward delivery             the gas collected at the end is hydrogen and hydrogen is lighter than air that is why we use the upward delivery or you can also say the downwards displacement of air                                                  [b] hydrogen +copper[ii]oxide⇒water+copper                                                                                  

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.