A saturated liquid mixture of 0.4 mole fraction n-hexane and 0.6 mole fraction n-octane is fed at a rate of 100 moles/h to a distillation column. The column contains a total condenser and a regular reboiler. The reflux ratio at the top of the column is 0.5. The distillate product is 0.95 mole fraction n-hexane, and the mole fraction of n-hexane in the stream from the reboiler is 0.05. A cooling coil is submerged in the liquid of the second plate from the top of the column. The coil removes sufficient heat to condense 50 mol % of the vapor rising from plate 3. Constant molal overflow can be assumed. Determine the number of plates required and the location of the feed plate.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.