Let's assume you have infinite amount of dilute aqueous solution of gold that only contains gold at a concentration of 1x10.10weight raction. if you would like to get the gold by evaporating water (say by heating from 25 °c to 100 °c at 1 atm pressure, how much energy you will need to produce 1 gm of gold. for industrial consumption, average cost of electricity is $0.0665 kw h. from steam table you may find that to evaporate water into steam at 100°c and 1 atm pressure, 2675.4 kj of energy needed per kg of water. what would be the cost per gram of gold from your production facility only on the basis of evaporation (cost of electric energy)? how does it compare with the market price? today's price of gold: $39.14/gm.

answer by yourhope:

how do models compare to real-world objects?

d. most models represent a real-world object in a simpler way.

: )

i'm pretty sure its b i might be wrong though!

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.