Answers and Explanations

REVIEW QUESTIONS

1 . B

KCl is  an  ionic   salt,   and therefore   should  be  soluble in  polar   solvents    and insoluble   in  nonpolar

solvents.   Water   is  a   highly  polar   liquid. The carbon  atom    in  carbon  tetrachloride,  CCl 4 , is

bonded  to  four    atoms,  so  the molecule    is  tetrahedral.    This    geometry    means   that    the individual

dipole  moments of  the bonds   cancel  and CCl 4   is  nonpolar.   Ethanol (CH 3 CH 2 OH)  has two carbon

atoms   in  tetrahedral arrangement;    most    of  the dipole  moments associated  with    the bonds   are

the same,   but the C   —   C   and C   —   OH  bonds   are different,  so  ethanol is  somewhat    polar.  Thus,

the polarities  of  the three   solvents    decrease    in  the following   sequence:   H 2 O   >   CH 3 CH 2 OH    >   CCl 4 ,

with    the solubility  of  KCl decreasing  along   that    sequence.

2 . A

A   1   M   NaOH    solution    means   that    there   is  1   mol of  NaOH    for every   liter   of  the solution.   We  are

interested, however,    in  a   final   volume  of  200 mL, which   is  a   fifth   of  a   liter.  Therefore,  0.2 mol of

NaOH    is  needed. The formula weight  of  NaOH    is  40, and so  the amount  of  NaOH    needed  is  0.2

mol ×   40  g/mol   =   8   g.

3 . C

When    a   solution    is  diluted,    more    solvent is  added,  yet the number  of  moles   of  solute  remains

the same.   To  solve   a   dilution    problem,    the following   equation    is  used:

MiVi    =   MfVf

where   i   represents  the initial conditions  and f   represents  the final   conditions. Therefore,  the

calculation to  solve   for the final   volume  is: