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AP Chemistry 8 Questions (multiple subjects, some multiple parts)

Detailed explanations/answers would be highly appreciated, I plan on using these questions to help study for for an upcoming final. If hand written please do not write in cursive for I have trouble reading it.

1.
(A) Calculate the density of NO2 gas at 0.970 atm and 35 degrees Celsius.
(B) Calculate the molar mass of a gas if 2.50 grams occupies 0.0875 liters at 685 torr and 35 degrees Celsius.

2. What molecular features make a polymer flexible? Explain how cross linking affects the chemical and physical properties of the polymer.

3.
(A) What is an ideal solution?
(B) The vapor pressure of pure water at 60 degrees Celsius is 149 torr. The vapor pressure of water over a solution at 600 degrees Celsius containing equal numbers of moles of water and ethylene glycol (a nonvolatile solute) is 67 torr. Is the solution idea according to Raoult's law? Explain.

4. The isomerization of methyl isonitrile (CH3NC) to acetonitrile (CH3CN) was studied in the gas phase at 2150 degrees Celsius, and the following data was obtained:
Time (in seconds) - [CH3NC] (M)
0s - 0.0165
2000s - 0.0110
5000s - 0.00591
8000s - 0.00314
12000s - 0.00137
15000s - 0.00074

(A) Calculate the average rate of reactions, in M/s, for the time interval between each measurement.
(B) Graph [CH3NC] vs time, and determine the instantaneous rates in M/s at t=5000s and t=8000s.

5. The equilibrium constant for the reaction 2NO(g) + Br2(g) <--> 2 NOBr(g) is
Kc = 1.3 X 10^-2 at 1000K.
(A) Calculate Kc for 2NOBr(g) <--> 2NO(g) + Br2(g)
(B) At this temperature does the equilibrium favor NO and BR2 or does it favor NOBr?

6. Which of the following cations will be the most acidic and why: Ca2+, Fe2+, Fe3+

7. A 1.00L solution saturated at 25 degrees Celsius with calcium oxalate (CaC2O4) contains 0.0061 grams of CaC2O4. Calculate the solubility product constant for this salt at 25 degrees Celsius.

8. The complexes [V(H2O)6]3+ and [VF6]3- are both known.
(A) draw the d-orbital energy level diagram for V(III) octahedral complexes.
(B) what gives rise to the color of the complexes?
(C) Which of the two complexes would you expect to absorb light of higher energy? Explain.

Solution Preview

1. (A) Calculate the density of NO2 gas at 0.970 atm and 35 degrees Celsius.
(B) Calculate the molar mass of a gas if 2.50 grams occupies 0.0875 liters at 685 torr and 35 degrees Celsius.

For this type of question, we could use the following formula (I include the detailed steps how we obtain it)
PV=nRT, n=m/M (m is the mass, M is the molar mass)
PV=m/MRT
PM=m/VRT (Based on the definition of density, ρ=m/V)
PM=ρRT
(A) In this question, M=46.01 g/mol
ρ=PM/(RT)=0.970*46.01/(0.0821*(35+273.15))=1.764 g/l
(B) M=ρRT/P=(2.50/0.0875)*0.0821*(35+273.15)/(685/760)= 801.94 g/mol
Note: when we use R=0.0821atm.L/(mol*K), we need to convert 685 torr to atm based on the following conversion:
1atm=760 atm

2. What molecular features make a polymer flexible? Explain how cross linking affects the chemical and physical properties of the polymer.
First, less cross linking would make polymers more flexible. In addition, use of plasticisers will make polymer more flexible. Third, increasing crystallinity or chain length will reduce flexibility of polymers. Cross linking is a type of bonding that occurs between two chains of polymer. As the amount of cross linking increases, the polymer become less flexible.It will also increase Tg. The Cross-linking also decreases the viscosity (the resistance to flow) of polymers. Cross-linked polymers are usually insoluble (don't dissolve) in solvents because the polymer chains are ...

Solution Summary

The solution assists with answer the AP chemistry questions based on multiple subjects and parts.

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