Download 10 States of Matter

South Pasadena • AP Chemistry
Name
10 ▪ States of Matter
Period
10.3
1. The diagrams show the results of paper
chromatography of four separate amino acids in
two different solvents.
Date
PROBLEMS
–
MIXTURES
2. In an experiment, a mixture of amino acids was
separated using paper chromatography and solvent
Y. The resulting paper is shown below.
(a) Use the table of Rf values below to decide
which of the labelled spots, P, Q or R is
arginine.
Amino Acid
Rf in Solvent X
Rf in Solvent Y
Alanine
Arginine
Glutamic Acid
Glycine
Tyrosine
Leucine
Proline
0.70
0.72
0.38
0.50
0.66
0.91
0.95
0.38
0.20
0.30
0.26
0.45
0.73
0.43
(a) Calculate the Rf value for amino acid B in (i)
Solvent A and (ii) Solvent B.
(b) Explain the difference in Rf value.
(b) In a separate experiment a mixture of alanine,
arginine and tyrosine was applied and solvent
X moved 20 cm up the paper. How far up the
paper from the origin would Tyrosine be
located?
(c) What is the correct order of the following steps
to describe the process of 2-way
chromatography? (number from 1-8)
 Calculate Rf values.
 Run the chromatogram in the 1st
solvent
 Measure the distance the spots and
solvent have moved
 Apply mixture to the chromatography
paper
 Spray with locating agent
 Run the chromatogram in the 2nd
solvent
 Rotate the paper
 Mark the paper
The diagram shows the result of a two-way
chromatogram.
3. What is the vapor pressure of a solution by mixing
35.0 grams of urea (CH4N2O) with 150.0 grams of
acetone (C3H6O) at 40°C? Assume urea is nonvolatile, and the vapor pressure of pure acetone is
400. torr at 40°C.
4. A sample of magnesium nitrate is added to 500 g
water.
(a) What mass of magnesium nitrate is required to
lower the freezing point of water to −12°C?
(b) What is the boiling point temperature of water
for this solution?
(d) Which letters correspond to amino acids that
are equally soluble in the first solvent that was
used?
(e) Explain how you can tell that Q and R are not
the same amino acid.
5. Which of the following solutions would you expect
to have the lowest freezing point? (The molality, m,
mol solute
is the kg solvent ratio.
a. 0.010 m NaCl
d. 0.050 m glycerol
b. 0.100 m sugar
e. 0.060 m Ca(NO3)2
c. 0.070 m KNO3
f. 0.075 m KCl
6. Consider a solution with 64 g of methanol
7. 0.64 g of adrenaline in 36.0 g of carbon
(CH3OH) and 69 g of ethanol (C2H5OH).
tetrachloride produces a boiling point elevation of
Methanol: MM = 32.04 g/mol, Pvap = 90 torr
0.49°C. What is adrenaline's molar mass? (kb
Ethanol:
MM = 46.07 g/mol, Pvap = 45 torr
carbon tetrachloride = 5.03 °C·kg·mol–1)
(a) What is the total vapor pressure of the solution?
(The total vapor pressure is the sum of the
vapor pressures of each component in the
solution.)
(b) What IMFs are involved in the substances?
Which has stronger intermolecular forces?
Why?
AP Chemistry 1993 #2
Elemental analysis of an unknown pure substance indicates that the percent composition by mass is as follows:
Carbon - 49.02%
Hydrogen - 2.743%
Chlorine - 48.23%
A solution that is prepared by dissolving 3.150 grams of the substance in 25.00 grams of benzene, C6H6, has a
freezing point of 1.12°C. (The normal freezing point of benzene is 5.50°C and the molal freezing-point depression
constant, kf, for benzene is 5.12 C°/molal.)
(a) Determine the empirical formula of the unknown substance.
(b) Using the data gathered from the freezing point depression method, calculate the molar mass of the unknown
substance.
(c) Calculate the mole fraction of benzene in the solution described above.
(d) The vapor pressure of pure benzene at 35°C is 150. mmHg. Calculate the vapor pressure of benzene over the
solution described above at 35°C.