Thermochemistry
Which of the following have a nonzero enthalpy of formation value?
A. Fe (s) B. Hg (l) C. Cu (l)
D. Br2 (l) E. N2 (g)
C
What are the signs of ∆H and ∆S for a reaction that is spontaneous only at high temperatures?
∆H is positive, ∆S is positive
Calculate the deBroglie wavelength in meters of a ball of mass 125 grams and velocity 90 m/s.
5.9 × 10-35 m
Which of the following sets contains only bent molecules?
A. H2S, HCN, CO2
B. CO2, HCN, H2O
C. H2S, CO, CO2
D. BF3, Cl2, O3
E. H2O, SO2, H2S
A fat-soluble compound would least likely dissolve in what?
A. Fat B. CHCl3 C. C6H14 D. Decanol (CH3(CH2)9OH)
B
For a certain reaction at constant pressure, ΔU is -125 kJ and 22 kJ of expansion work is done on the system. What is ΔH for this process?
-103 kJ
What is the equilibrium constant K for the following reaction at 300 K? CaCO3(s) → CaO(s) + CO2(g)
ΔGf° (kJ/mol) = -1128 -604 -394.4 respectively
2.72 × 10-23
Draw a 4dyz orbital, label all its nodes
(optional: shade the orbital to indicate phases +200 points)
bleh
According to Molecular Orbital (M.O.) theory, which statements below are true? (can contain more than 1 right answer)
1. A bonding molecular orbital is lower in energy than the atomic orbitals of which it is composed.
2. A molecule with an even number of electrons must always be diamagnetic.
3. There are as many molecular orbitals as there are atomic orbitals.
4. All molecules contain pi bonds.
5. There are as many sigma bonds as pi bonds in a molecule.
1 and 3
You have two containers that are both closed systems. They both start with the same volume of the same liquid, and both have the same amount of gas dissolved in the liquid phase. 50% of the liquid is removed from the first container (container A), while 25% of the liquid is removed from the second container (container B). After 24 hours at ambient conditions, which container has more gas dissolved in the liquid?
A. Container A B. Container B
C. Both are the same.
A
Which of the following combinations are correct?
A. N2 (l) → N2 (g), system does work on the surroundings
B. Cl2 (g) → Cl (g), no work is done
C. CH3OH (l) + O2 (g) → CO2 (g) + H2O (l), surroundings do work on the system
D. All are correct
A or C
For a standard reaction where A → B + C the ΔG° is -10 kJ. If the amounts of B and C are added such that Qc > Kc how will ΔG compare to ΔG°?
A. ΔG > ΔG° B. ΔG = ΔG°
C. ΔG < ΔG° D.Not enough information is given
A
Arrange the following from left to right in order of increasing radius.
S2-, F, F+, Cl, S
Which atom has a larger Zeff, S or Cl?
Which atom (F, Cl, or S) would experience the least shielding?
F+ < F <Cl < S < S2-
Cl
F
Draw the 3 possible Lewis structures (i.e., 3 most likely structures) of thiocyanide (SCN─). Assign formal charges to all elements in all structures. Circle the most probable structure based on formal charges.
we figure out together
Iodine, like most substances, exhibits a typical phase diagram in three phases: solid, liquid, and vapor. The triple point of iodine is at 90 Torr and 115°C. Which of the following statements concerning I2 must be true? A. I2 (l) cannot exist above 115°C.
B. I2 (l) cannot exist at a pressure of 1 atm.
C. I2 (l) cannot have a vapor pressure greater than 90 Torr.
D. I2 (l) cannot exist at a pressure of 10 Torr.
E. I2 (l) is less dense than I2 (g)
D
A 1.000 kg piece of iron is removed from a furnace at 1200.0°C and immersed in 1.000 kg of water initially at 20.0°C. Assuming no heat is lost to the surroundings, calculate the mass of liquid water remaining after thermal equilibrium is reached at 100.0°C. The specific heat of water is 4.184 Jg-1K-1 and that of iron is 0.450 Jg-1K-1. The enthalpy of vaporization for water is 40.65 kJ/mol.
92 g remaining
Consider the following unbalanced reaction at 50.0°C: I2(s) + Cl2(g) ⇌ ICl(g)
A. If the ΔGf of ICl(g) is -5.46 kJ/mol, determine ΔGo for the reaction.
B. Calculate the value of ΔG in kJ/mol at 50.0°C when the system contains 100.0 g of I2(s), Cl2(g) at partial pressure of 0.20 atm, and ICl(g) at partial pressure of 0.80 atm. Under these conditions, is the forward reaction spontaneous?
A) –10.92 kJ/mol
B) −7.80 kJ/mol, yes
Write the symbol and electronic configuration of the: A. 3rd row alkali metal.
B. 4th row alkaline earth metal.
C. 2nd row halogen.
D. Element in IVA group and in the fifth row.
E. Which of the elements of group IVA have d electrons in their electronic configurations?
A. Na: 1s2 2s2 2p6 3s1
B. Ca: 1s2 2s2 2p6 3s2 3p6 4s2
C. F: 1s2 2s2 2p5
D. Sn: [Kr] 5s2 4d10 5p2
E. Ge, Sn and Pb
Complete the MO energy level diagram for O2+ atom
A. Fill in the electrons using arrows (↑ and/or ↓) for the atomic and molecular orbitals in the molecular orbital diagram below.
B. Designate all the energy levels in the MO diagram.
C. Calculate the bond order for O2+
D. Is O2 + a paramagnetic or diamagnetic chemical species?
See Enderle reader
Boiling Flask Demo. An Erlenmeyer flask of boiling water is removed from its heat source and immediately capped. At this point the water stopped boiling. The flask is then submerged into an ice-water bath. Answer the following questions using 4 words or less regarding this process.
A) What was the temperature of the water when quenched?
B) What happened to the water in the flask after quenched in ice bath?
C) What happened to the pressure in the flask after quenched?
D) For boiling to occur in this system, the vapor pressure was equal to what pressure?
A) <100 C
B) Boiled
C) Decreases
D) The flask pressure
1. Name any property that is a state function.
2. What type of system would most likely result in the internal energy (U) being constant?
3. Considering the first law, what term is often negligible in a chemical reaction such that ΔU is approximately equal to ΔH?
4. What type of system allows for energy transfer across a boundary but not mass transfer?
5. What type of function is independent of path?
6. This type of function depends only on the current state of the system thus making the pathway irrelevant.
7. The quantity of heat exchanged between the system and surroundings during a chemical reaction.
8. Heat at constant pressure.
1. (T, P, V, m, U, H, etc.)
2. isolated
3. work
4. closed
5 and 6. state
7. heat of reaction
8. enthalpy
Consider the oxidation of iron metal to Fe2O3 solid at 25°C: 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)
ΔH°sys = -1648.4 kJ
Sm° (JK-1mol-1) 27.3 205.0 87.4 respectively
A. (3 points) Calculate the entropy change of the surroundings corresponding to this chemical change at standard conditions.
B. (3 points) Calculate the entropy change of the chemical system at standard conditions.
C. (3 points) Determine the value and sign of the entropy change of the universe. Does this reaction have a tendency to take place at standard state conditions?
D. (5 points) Calculate ΔG°f for Fe2O3(s) at 25°C.
E. (2 points) A reaction with ΔG° = -200 kJ/mol has an equilibrium constant equal to 1x1035, which indicates practically a 100% reaction. With this information in mind estimate the pressure of oxygen at equilibrium if you start with just Fe2O3(s).
A) ΔSo = + 5.53 kJ/K
B) ΔSo sys = - 0.55 kJ/K
C) + 4.98 kJ/K
D) ΔG°rxn = -1484.5 kJ
E) Effectively 0 atm
Write the quantum numbers of all the electrons in a neutral magnesium atom from lowest to highest energy.
Good luck
bleh
Draw the Lewis electron dot diagrams for the following chemical species and include all reasonable resonance diagrams, if any.
A. PO43-
B. C2O42-
C. CH3NH2
we draw together
The vapor pressure of pure benzene (B) and pure toluene (T) at 25°C is PB = 0.12 atm and PT = 0.04 atm, respectively. All questions below are at 380 K.
A. (3 points) First determine the pure vapor pressure of benzene at 380 K given that Hvap(B) = 30.8 kJ/mol.
B. (3 points) Next determine the pure vapor pressure of toluene at 380 K given that Hvap(T) = 33.4 kJ/mol.
C. (5 points) Use your results from parts A and B to find the mole fraction of benzene liquid in the mixture. The normal boiling point of the mixture is 380 K.
D. (3 points) Use your result in part C, find the partial pressure of benzene above the solution.
E. (2 points) Use your result in part C to find the mole fraction of toluene liquid in benzene liquid.
F. (3 points) If 5.0 g of benzene (C6H6) is used, what must the mass of toluene (C7H8) liquid be in the solution?
A) 1.8 atm
B) 0.73 atm
C) 0.25
D) 0.45 atm
E) 0.75
F) 17.7g toluene