Twenty-seven pounds (27 lb) of chlorine gas is used for treating 750,000 gal of water each day. The chlorine used up by the microorganisms in the water is measured to be 2.6 mg/L. What is the residual (excess) chlorine concentration in the treated water?

The correct answer is 1.778 milligrams per liter.

Explanation:

Based on the given information, the concentration of chlorine gas given is 27 pounds or 27*453.59 = 12327.93 grams.

The quantity of water given is 750000 gallons or 750000 * 3.754 = 2815500 L

The concentration of chlorine used up by the microorganism is 2.6 mg/L or 0.0026 gm/L.

Thus, for 2815500 L of water, the amount of chlorine used is,

= 2815500 * 0.0026

= 7320.3 grams

The left quantity of chlorine is 12327.93 - 7320.3 = 5007.63 grams

The concentration of residual chlorine is,

= 5007.63 g/2815500 = 0.00177859 or 1.778 mg/L.

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.

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