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Chem 162 Final Exam (1)
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Chem 162 Final Exam (1)
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Chem 162 Final ExamIf 0.100 mol of solute is added to 0.500 L of solvent with a density of 0.790 g/mL,
the molality of the solution is
a. 0.166 m
b. 0.253 m
c. 1.27x10^-4 m
d. none
e. 0.200 m - CORRECT ANSWER-b.
This question counts the weight of two questions. The half-life of a reactant in a
first-order reaction was measured to be 6.10 hours. If the starting concentration
is 1.00 M, what is the remaining concentration after 7.43 hours?
The first-order rate equations are
ln [A]t = -kt + ln [A]0 and t1/2=0.693/k
Calculate k, the rate constant and select the correct units for k (leave one extra
significant figure to prevent rounding error).
Calculate the remaining concentration after 7.43 hours. - CORRECT
ANSWER-k=0.01136 1/hr
0.430 M
Adding 17.5 g of an unknown compound to 100.0 g of water results in a freezing
point lowering of -1.80 °C. Calculate the molality and molar mass of the unknown
compound. You may assume that the density of water is 1.00 g/mL, and Kf for
water is 1.86 °C/m.
Equation: ΔTf = Kf m - CORRECT ANSWER-0.9677m
1.81 g/mol
Select the correct expression for the rate of the following reaction, in terms of the
concentrations of reactants and products.
2 H2O2 → 2 H2O + O2 - CORRECT ANSWER-rate= -1/2[H2O2]/d. t
=1/2[h2o]/d.t
=1/1[o2]/d. t
,the definition of molality (m) is
a. mol solute per liter of solution
b. none
c. mol solute per liter of solvent
d. mol solute per kilogram of solution
e. mol solute per kilogram of solvent - CORRECT ANSWER-e.
the rate law for a second-order reaction is written - CORRECT
ANSWER-rate=k[A]^2
You would expect a molecule of the formula C8H18 to be most soluble in
a. C6H6
b. none
c. H2O
d. CH3OH
e. NH3 - CORRECT ANSWER-a.
gases are most soluble in water at
a. high temps and low pressures
b. high temps and high pressures
c. low temps and low pressures
d. low temps and high pressures - CORRECT ANSWER-d.
If a nonvolatile solute is added to a solvent, you would expect the mixture to
show
a. Freezing point depression and boiling point elevation
b. Freezing point elevation and boiling point depression
c. None of these - CORRECT ANSWER-a.
If you are given the rate constant of a reaction at four different temperatures, how
would you calculate the activation energy from the equation
ln k= -Ea/RT+ln A
plot what as x?
plot what as why?
activation energy calculated from? - CORRECT ANSWER-x: 1/T
y: ln k
Ea: slope=-Ea/R
, In the energy diagram below, the activation energy of the forward reaction is
shown by which arrow? - CORRECT ANSWER-bottom of curve to top of curve
If a solution contains 30. ppm (parts per million) of a pollutant, what percentage is
this?
a. 3.0 x 10-4 percent
b. 0.30 percent
c. None of these
d. 3.0 x 10-5 percent
e. 0.0030 percent - CORRECT ANSWER-e.
The effect of a catalyst on the activation energy of a reaction is to
a. Lower the activation energy
b. Raise the activation energy
c. None of these - CORRECT ANSWER-a.
An elementary reaction is a reaction that occurs in a single step. - CORRECT
ANSWER-T
The step that determines the rate of an overall reaction is the fast step. -
CORRECT ANSWER-F
According to the Arrhenius equation, the rate constant k depends on
temperature. - CORRECT ANSWER-T
For any reaction, the order of the reaction is given by the balancing coefficients. -
CORRECT ANSWER-F
A catalyst is used up in a chemical reaction. - CORRECT ANSWER-F
If the following reaction is at equilibrium, what happens if we add more CoO(s) to
the following reaction:
CoO(s) + H2(g) ⇄ Co(s) + H2O(g)
Select one:
a. The reaction shifts backward
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