Questions from Previous Chemistry 116 Exams
Solutions
1.The alcohol, HOCH2(CH2)6CH2OH, with two OH groups is only slightly soluble in
water. A similar alcohol of the form, CH3(CH2)6CH2OH, with only one OH group
would be expected to:
A. have the same solubility in water as alcohol with two OH groups.
B.be less soluble in water than the alcohol with two OH groups.
C.be more soluble in water than the alcohol with two OH groups.
D.be less soluble in a nonpolar solvent such as dichloroethane.
ANS. B
2.What is the mole fraction of water in a solution containing 36 g of water (MM = 18
g/mol) and 60 g of acetic acid (MM = 60 g/mol).
ANS. .667
3.Calculate the molar concentration of acetic acid in a solution containing 55% acetic
acid (MM = 60.0 g/mol) in water assuming the solution has a density of 1.07 g/ml.
ANS.9.8
4.The vapor pressure of pure water at 25oC is 24 torr and the vapor pressure of ethyl
alcohol at this temperature is 60 torr. What is the total vapor pressure (in torr) over a
solution containing 1.0 mole of water and 4.0 mole of ethyl alcohol?
ANS. 52.8
5.Assume that incremental amounts of a volatile solute are added to a solvent so that the
mole fraction of solute varies from 0 to 1. A plot of the partial pressure of the solute vs.
mole fraction of solute will:
A] be linear with slope equal to the vapor pressure of the pure solute.
B.be linear with slope equal to the vapor pressure of the pure solvent.
C. be linear with slope equal to the sum of the vapor pressures of pure solvent and pure
solute.
D. vary exponentially with the mole fraction of the solute.
ANS. A
6.If a solution containing 2.5 x 10-5 mol/L of the blue dye in a mouth wash preparation
has a percent transmittance of 43%T, what is the molar concentration of the blue dye in a
mouth wash solution that has a percent transmittance of 73%T at the same wavelength?
ANS. 9.3x 10 TO THE POWER -6
7.For spectrophotometric measurements such as those done with the mouthwash dyes:
A. absorbance decreases exponentially with increasing concentration.
B. percent transmittance increases linearly with increasing concentration.
C. percent transmittance increases exponentially with increasing concentration.
D. percent transmittance decreases exponentially with increasing concentration.
absorbance is inversely proportional to concentration.
ANS.D
8.The alcohol, CH3(CH2)6CH2OH, is only slightly soluble in water. A similar alcohol of
the form, HOCH2(CH2)6CH2OH, with an additional OH group added would be
expected to:
A.have the same solubility in water as alcohol with a single OH group.
B.be less soluble in water than the alcohol with a single OH group.
C.be more soluble in water than the alcohol with a single OH group.
D.be more soluble in a nonpolar solvent such as dichloroethane.
ANS.C
9.If the water molecule had a linear rather than a bent structure, we would expect that:
A. both the boiling and freezing temperatures would be higher.
B. the boiling temperature would be higher but the freezing temperature would be lower.
C. both the boiling and freezing temperatures would be lower.
D. salts such as sodium chloride would be even more soluble in the linear structure than
the bent structure.
ANS. C
10. What is the mole fraction of water in a solution prepared by mixing 180 g of water
(MM = 18 g/mol) and 42 g of ethyl alcohol (MM = 42 g/mol).
ANS..909