1. A solution containing 27.00 mg of an unknown protein per 28.5 mL solution was
ID: 1030124 • Letter: 1
Question
1. A solution containing 27.00 mg of an unknown protein per 28.5 mL solution was found to have an osmotic pressure of 3.90 torr at 42 C. What is the molar mass of the protein? Units must end in g/mol.
2. Calculate the vapor pressure of a solution containing 26.7 g of glycerin (C3H8O3) in 128 mL of water at 30.0 C. The vapor pressure of pure water at this temperature is 31.8 Torr. Assume that glycerin is not volatile and dissolves molecularly (i.e., it is not ionic) and use a density of 1.00 g/mL for the water. Units must end in torr.
3. Calculate the freezing point and boiling point in each solution, assuming complete dissociation of the solute. Assume the normal freezing point and normal boiling point of water are precise to the hundredths place.
Part A
Calculate the freezing point of a solution containing 6.2 % KCl by mass (in water).
Part B
Calculate the boiling point of a solution above.
4. Consider the following reaction:
CO(g)+2H2(g)CH3OH(g)
An equilibrium mixture of this reaction at a certain temperature was found to have [CO]= 0.115 M , [H2]= 0.116 M , and [CH3OH]= 0.190 M. What is the value of the equilibrium constant (Kc) at this temperature?
Units must end in M.
6. Consider the following reaction:
Fe3+(aq)+SCN(aq)FeSCN2+(aq)
A solution is made containing an initial [Fe3+] of 1.2×103 M and an initial [SCN] of 8.1×104 M . At equilibrium, [FeSCN2+]= 1.6×104 M. Calculate the value of the equilibrium constant (Kc).
7. The half-life for the radioactive decay of U238 is 4.5 billion years and is independent of initial concentration. How long will it take for 20% of the U238 atoms in a sample of U238 to decay?
t =
8. A group of CHEM L112 students generated these data during the chemical proportionality experiment.
Part A
Write the balanced chemical reaction that occurs when solid sodium carbonate is added to a solution of hydrochloric acid. Include states of matter.
Part B
A student found that 0.2045 g Na2CO3 was required to reach the equivalence point when added to 23.39 mL of a solution of HCl of unknown concentration. What is the concentration of the acid solution?
9. The reaction between chlorine dioxide and ozone is relevant to the study of atmospheric ozone destruction. The value of the rate constant for the reaction was measured at four temperatures. The results are as follows:
Calculate the activation energy for this reaction. (Hint: use Excel)
Units must end in kJ/mol
10. A student collected time (t) and concentration ([CV+]) data at 295 K for the reaction CV+ + OH– CVOH. These time and concentration data are shown in the table.
What is the order of the reaction with respect to CV+?
11. The following questions pertain to the Total Serum Iron Assay experiment executed in CHEM L112.
Part A
How many mL of a 100 mg/dL Ferrozine solution are needed to complex 5.2×108 moles of iron? Write the value with the appropriate units.
Part B
How many moles of Fe3+ can be reduced by 1.5 mL of 0.235 M hydroxylamine solution? Write the value with the appropriate units.
Part C
As part of this laboratory, you may have to add iron to a solution. If you have 16 mL of a solution that contains 31 g dL-1, how many mL of 500 g dL-1iron must be added to reach a concentration of 150 g dL-1? Write the value with the appropriate units.
12. Consider the following data:
Part A
Which one statement BEST explains the increased water solubility of dimethylsulfoxide and dimethylsulfone relative to dimethylsulfide?
Tf = ? C -2.3 -2.4 -2.5 2.6 -2.7 Slope y-intercept y-0.000290t - 2.30 2.8- 0 500 1000 1500 2000 Time (s)Explanation / Answer
1)
P= 3.90 torr
= (3.90/760) atm
= 0.005132 atm
T= 42.0 oC
= (42.0+273) K
= 315 K
use:
P = C*R*T
0.005132 = C*0.08206*315.0
C =0.0001985 M
volume , V = 28.5 mL
= 2.85*10^-2 L
use:
number of mol,
n = Molarity * Volume
= 0.0001985*0.0285
= 5.658*10^-6 mol
mass(solute)= 27.00 mg
= 0.027 g
use:
number of mol = mass / molar mass
5.658*10^-6 mol = (0.027 g)/molar mass
molar mass = 4.77*10^3 g/mol
Answer: 4.77*10^3 g/mol
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