Download sample questions test 1

Chem 209
Review questions for test 1
a. Moles of solute per liter of solution is the definition of
mole fraction
molarity
molality
parts per million
b. Which one of the following does NOT usually increase with temperature?
osmotic pressure
solubility of a gas in water
vapor pressure
solubility of a salt in water
c. Which one of the following forces is most important for the solubility of octane in hexane?
hydrogen bonding
ion-dipole forces
dipole-dipole forces
London forces
d.
If an aqueous solution has a boiling point of 101.00 oC at 1 atm, what is its freezing point?
( for water Kf = 1.86 oC m, Kb = 0.512 oC m)
1.86 oC
3.63 oC
- 1.86 oC
- 3.63 oC
e.
Which one of the following is most likely to be soluble in a nonpolar solvent?
H2O
CH3OH
Cl2
KCl
f.
Which one of the following is likely to be most soluble in H2O?
CH3OH
CH3CH2CH2OH
I2
CH3CH2CH3
g. Which one of the following will always DECREASE the amount of O2 dissolved in water?
increasing the temperature and increasing the pressure of O2 above the water
increasing the temperature and decreasing the pressure of O2 above the water
decreasing the temperature and increasing the pressure of O2 above the water
decreasing the temperature and decreasing the pressure of O2 above the water
h. Which one of the following statements is TRUE?
All salts easily dissolve in water
Energy is always required to break the bonds in an ionic crystal
When NaCl dissolves it breaks down into Na and Cl atoms
Salts dissolve readily in CH3CH2CH2CH2CH2CH3
i. A colligative property is a property of a solvent that
depends on the molecular weight of the solvent,
depends on the amount of solute
depends on the total mass of the solvent
depends on the volume of the solution
j. If two salt solutions are separated by a semipermeable membrane there will be a net flow of
solvent from the low concentration solution to the high concentration solution
solute from the high concentration solution to the low concentration solution
solvent from the high concentration solution to the low concentration solution
solute from the low concentration solution to the high concentration solution
k. The vapor pressure of a liquid decreases when
temperature increases
a nonvolatile solute is dissolved
the pressure above the solution is lowered
the liquid is transferred to a smaller container
1
Chem 209
Review questions for test 1
l. A solution is made by mixing one mole of toluene with one mole of benzene at 25 C. For
pure benzene the vapor pressure is 80 torr and for pure toluene the vapor pressure is 50
torr. The mole fraction of toluene in the vapor above the solution is
greater than 0.5
equal to 0.5
less than 0.5
m. Which one of following aqueous solutions will have the lowest freezing point
0.5 m NaCl
0.25 m KCl
0.2 m MgCl2
0.1 m CoCl3
n. Which one of the following forces is most important for the high solubility of KCl in water
hydrogen bonding
London forces
ion-dipole forces
dipole-dipole forces
o. The solubility of a gas is water is highest for which conditions of temperature and pressure?
high P, high T
high P, low T
low P, high T
low P, low T
p. Which one of the following is NOT a colligative property?
freezing point depression
temperature
osmotic pressure
vapor pressure lowering
q. Which one of the following combinations would NOT be likely to form a solution
ionic solid and non-polar liquid
ionic solid and polar liquid
polar solid and polar liquid
non-polar solid and non-polar liquid
r. Blood cells have a semipermeable membrane and their fluid contains dissolved ions. When
blood cells are placed in a concentrated salt solution they shrink because
ions pass through the cell membrane by osmosis
water passes through the cell membrane by osmosis
water passes through the cell membrane by reverse osmosis
salt passes through the cell membrane by osmosis
s. Which one of the following is a colloid that has a solid suspended in a liquid?
emulsion
sol
foam
t.
aerosol
A soap molecule contains
a polar group at the end of a long polar chain
a nonpolar group at the end of a long polar chain
a nonpolar group at the end of a long nonpolar chain
a polar group at the end of a long nonpolar chain
u. Which one of the following statements is TRUE?
A mixture of liquids is always a solution
A colloid is a solution
A solution may have more than one phase
Air is an example of a solution
_______________________________________________________________
Circle the member of each of the following pairs that is likely to be more soluble in the indicated
solvent.
CH3CH2CH2OH or Br2
CH3CH2CH2CH2CH2OH or CH3OH
CH3OH or I2
in water
in hexane
in ethanol
2
Chem 209
Review questions for test 1
_______________________________________________________________
a. When 8.0 g of an unknown compound is dissolved in 500.0 g of carbon tetrachloride, CCl4,
the freezing point of the solution is -30.7 °C. The freezing point of pure carbon tetrachloride is 22.3 °C. (Kf = 29.8 C kg mol-1 for CCl4)
a. Find the molality of the solution.
b. Find the molecular weight of the unknown compound.
__________________________________________________________
The vapor pressure of pure water at 25 C is 23.8 mm Hg. What is the vapor pressure of a
solution made by adding 35 g of urea to pure water. Urea is a nonvolatile, nonelectrolyte that
has a molecular weight of 60 g/mol.
a. Find the vapor pressure of the solution at 25 C.
b. Assuming that the volume of solution in part a. is 200 m, find the osmotic pressure in torr of
this solution at 30 C.
__________________________________________________________
2. The boiling point of pure benzene is 80.16C. A solution of 2.15 g of a solid dissolved in 20
g. of benzene boils at 81.10 C. Kb for benzene is 2.53 C/m. Assume that the solution is a
nonelectrolyte.
a. Find the molality of the solution.
b. Find the molecular weight of the unknown compound.
__________________________________________________________
A solution is made by adding 10.0 g of NaCl (FW = 58.4 g mol to 100.0 g of H2O (MW =
18.0 g mol). The vapor pressure of pure H2O is 18 torr at 20 C.
a. Find the vapor pressure of the solution at 20 C.
b. Find the freezing point of this solution. (Kf = 1.86 C/m for water)
__________________________________________________________
3
Calculate the osmotic pressure in torr for 1000 mL of an aqueous solution containing 600.0 g of
glucose. Assume the temperature is 25 C. (MW = 180.0 g/mol for sucrose)
Calculate the vapor pressure for the same solution. The vapor pressure of pure water is 23.8
torr at 25 C. Assume that 1.00 mL of water weighs 1.00 g.
___________________________________________________________________
Find the osmotic pressure in torr for a solution made by adding 20.0 g of NaCl (FW 58.44) to
200 mL of water. Assume the temperature is 20oC.
_______________________________________________________________
Assume that the partial pressure of O2 above a solution is 150 mm Hg and the partial pressure
of N2 is 610 mm Hg. For water at 20 oC, the Henry’s law constant for O2 is 1.43 x10-3 mol L-1
atm-1 and for N2 is 7.34x10-4 mol L-1 atm-1
What is the molarity of O2 in solution?
What is the mole fraction of O2 in solution? Assume that the density of water is 1.00
g/mL. FW O2 = 32 g/mol, FW H2O = 18 g/mol.
3
Chem 209
Review questions for test 1
Is there more N2 or O2 dissolved in the water? Show calculations to demonstrate your
conclusion.
___________________________________________________________________________
a. Which one of the following DOES NOT have cis and trans isomers?
2,3-dichloro-2-butene
1,1-dichloro-1-butene
2-chloro-2-butene
1,2-dichloro-propene
b Which one of the following molecules could be used to make a chain growth (addition)
polymer?
methanol
propene
methyl ethyl ether
ethane
c. Which one of the followings statements is FALSE?
Proteins are made up from amino acids linked together by condensation reactions
The genetic code is stored in the sequence of the bases in DNA
The -helix is an important structure for proteins
A nucleotide contains phosphate group, an ether and an organic base
d.
Which one of the following compounds is a saturated hydrocarbon?
4-Pentene
2-butyne
3-methyl 2-pentene
2-methylpropane
e. How many isomers are there for the formula C2H2Cl2 ?
1
2
3
4
f. Which one of the following is a polysaccharide that is used to store energy in plants?
fructose
starch
glucose
glycogen
g. Which of the following is not part of DNA?
phosphate
base
sugar
amino acid
h. Which one of the bonds in the DNA double helix structure are the weakest?
the bonds between the bases
the bonds between the phosphate and sugar
the bond between the sugar and the base
the bond between the base and phosphate
i. How many isomers are there for the formula C3H6Br2?
2
3
4
j. One of the products of a condensation reaction is always
an ether
a protein
an acid
5
water
k. Which one of the following statements is TRUE?
benzene is an alkene
cyclohexane is an saturated hydrocarbon
alkynes sometimes have cis-trans isomers
alcohols act as bases
l. How many different alcohols have four carbons? Do not consider compounds with double
bonds or rings
4
Chem 209
Review questions for test 1
1
2
3
4
m. Which one of the following formulas most likely corresponds to a carbohydrate?
C6H12O6
C18H38O2
C6H12OH
C6H12
n. Which one of the following is an aromatic compound
methyl alcohol
methyl amine
2 –methylpropene
methyl benzene
o. Which one of the following statements is TRUE about DNA?
A nucleotide consists of a phosphate group, an ether and an organic base
The code for an amino acid is contained in three consecutive bases on the chain
The main DNA structure is the -helix
The pattern of bases in DNA contains information on the constructions of polysaccharides
__________________________________________________________
Draw the products of the following reactions
a) trans-2-pentene and Br2
b) the reaction between propanoic acid (CH3CH2COOH) and methanol
c) show a reaction between the two amino acids shown below to form a peptide bond.
H
O
C
H2N
NH2
C H
OH
+
O
CH
CH3
OH
C

__________________________________________________________
Draw the structures for molecules with the formula C5H10. Name all compounds. (1 point per
correct structure, 1 point per correct name)
__________________________________________________________
Draw the structures of the following.
3-pentanol
2-hexanone
2,6-dimethyl-3-heptene
3-methyl butanal
2,2,4-trimethylpentane
________________________________________________________________________________
10. (5 pts) Identify the class (alcohol, alkane, alkene, alkyne, amine, amide, amino acid,
aldehyde, aromatic, carboxylic acid, ether, ester, ketone) that best describes the following
molecules. R and R’ are hydrocarbon groups
5
Chem 209
Review questions for test 1
Identify each of the four following structures as (amino acid, alkane, alkyne, alkene, aromatic,
carbohydrate, dipeptide, dissacharide, nucleotide, tripeptide)
Consider the molecule shown below. Use asterisks to indicate the chiral carbons.
_________________________________________________________
Draw the structures for four compounds with the formula C4H8. Name all compounds. (1 point
per correct structure, 1 point per correct name, 8 points max)
_________________________________________________________
Draw the structures for five pentenes with the formula C6H12. Name all compounds. (1 point per
correct structure, 1 point per correct name, 10 points max)
6