Akcl solution is prepared by dissolving 40.0 g kcl (molar mass = 74.55 g/mol) in 250.0 g of water (molar mass = 18.01 g/mol) at 25°c. what is the vapor pressure of the solution if the vapor pressure of water at 25°c is 23.76 mm hg?
a) 20.5 mm hg
b) 22.1 mm hg
c) 22.9 mm hg
d) 24.7 mm hg

Option (B) is the correct answer.

Explanation:

The given data is as follows.

    mass of KCl = 40 g,           mass of water = 250.0 g

Hence, number of moles of KCl will be calculated as follows.

             No. of moles =

                                  =

                                  = 0.537 mol

Number of moles of water will be calculated as follows.

            No. of moles =  

                                 =

                                 = 13.9 mol

Also, mole fraction of KCl will be calculated as follows.

                              =

                              =

                              = 0.037

Hence, calculate the vapor pressure of the solution as follows.

Here, i = 2 because KCl on dissociation produces 2 ions that is, and .

                  = 22.1 mm Hg

Thus, we can conclude that the vapor pressure of the given solution is 22.1 mm Hg.

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.