In the distillation technique called rectification, the condensing vapour and boiling liquid streams are passed a rectifying column in intimate countercurrent contact. the more volatile components tend to transfer from the liquid to the vapor and less volatile components to the liquid. often the energy relations are such that the number of moles of both liquid and vapor is constant during the process, and for every mole of liquid vaporized there is a mole of vapor condensed. In a specific rectification process , operating on ethanol and water mixtures, the vapor and liquid streams entering and leaving the column are those given in the table ethanol water mole% moles liquid entering top 75.1 24.9 liquid leaving bottom 25.1 74.9 vapor entering bottom 40.2 59.8 vapor leaving top 77.3 22.7 calculate the numbers of moles of vapor flowing up the column per mole of liquid flowing down the column.