If the vapor pressure of an aqueous solution containing 6.00 moles of a nonvolatile solute has a vapor pressure of 19.8 torr, and given that the vapor pressure of water at room temperature is 23.7 torr, how many total moles are present in solution?

36.4 moles

Explanation:

This is a problem where a solute is added to water and this then decreases the vapor pressure of the water from what it was when it was pure.  The amount it will decrease the vapor pressure is directly related to the mole fraction of the solute (or put another way, the mole fraction of the water).

mole fraction of water x vapor pressure of water = vapor pressure of solution.  In equation form it is ...

Psolution = Xsolvent x P0solvent

We can solve for Xsolvent which is the mole fraction of the water.

Xsolvent = Psolution/Posolvent

Xsolvent = 19.8 torr/23.7 torr = 0.835

Since there are 6.00 moles of solute, we can find total moles present in solution.

x moles water/6.00 moles solute + x moles water = 0.835

x = 30.4 moles of water

Total moles present in solution = 6.00 moles + 30.4 moles = 36.4 moles

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.