Bootcamp Questions, Continued! Flashcards
An equilibrium mixture for the reaction A⇌B has a Kc = 0.40 at 350K.
Which of the following statements is true regarding a A⇌B mixture with a Qc = 20 at 350K?
A. The reaction will proceed to the right, forming more product to reach equilibrium
B. Once the reaction reaches equilibrium, the concentration of B will be greater than A
C. The concentrations of A and B are equal, and the reaction has reached a state of equilibrium
D. To reach equilibrium, the concentration of A will increase while the concentration of B will decrease
E. Kc will increase and Qc will decrease, and eventually equalize at Kc = 10, Qc = 10
D
Since Qc > Kc, the reaction will proceed to the left to reach equilibrium. The concentration of A will increase, and the concentration of B will decrease. The equilibrium constant will remain unchanged since only temperature can change the magnitude of K. Because K is less than 1, the amount of B is less than that of A at equilibrium.
As we know from general chemistry principles, two (equal/unequal) concentrations will tend to _____ due to entropy,
unequal, equalize
C
The normal freezing point is the freezing point (solid-liquid) at 1 atm. Similarly, normal boiling point is the boiling point (liquid-gas) at 1 atm.
We can estimate these values from the graph by drawing a horizontal line at 1 atm and estimating the temperature at the point where it crosses the solid-liquid line (freezing point) and liquid-gas line (boiling point) as shown below. The normal boiling point is approximately 215°C and the normal freezing point is approximately 110°C.
A fixed sample of an ideal gas occupies a volume of 1.2 L at 30°C and 1.0 atm. What volume will the gas occupy if the temperature is increased to 60°C at constant pressure?
All of the following statements accurately describe why mercury forms a convex meniscus in a glass thermometer EXCEPT one. Which one is the EXCEPTION?
A. The molecular forces of cohesion exceed the forces of adhesion.
B. Mercury tends to become ionized and the net charge repels the glass.
C. Nonpolar and polar molecules tend to repel each other.
D. The forces between mercury molecules are stronger than the forces between the mercury and glass.
E. Capillary action pulls the edges of the mercury down.
B
The empirical formula of a compound is found to be CO3. What is the molecular formula if the molar mass of the compound is 180 g/mol?
A. CO9
B. C2O6
C. C3O9
D. C4O12
E. C6O18
C
CO3 = 60 g/mol
180 / 60 = 3x multiplier
CO3 × 3 = C3O9
If the forward reaction had the same entropy as the reverse reaction, what would occur?
NOTHING - if these are the same, a reaction would not occur!
Plot for second order
For multiplying and dividing, the number of significant figures is determined by the measurement with the (largest/fewest) amount of significant figures.
For adding and subtracting, the answer must have the same amount of decimal places as the measurement with the (largest/fewest) number of decimal places. This reduces error when taking measurements.
multiplying, dividing, subtracting, or adding = use whichever has the LEAST sigfigs
Parallax error may occur when:
A. an experiment does not account for changes in altitude.
B. a measurement is not properly converted between the metric and customary systems.
C. a meniscus in a buret is not observed directly straight on.
D. an object under water is observed at an angle from above the surface.
E. the concentration of an acid to be used in a titration is not first checked against a standard.
C
Compare and contrast crystalline and amorphous solids.
Crystalline solids
- long range order = This means there is a consistent, crystal lattice network of atoms that is well defined, and repeated throughout the structure
- have sharp, well defined, characteristic melting temperatures, and break with a cleavage along a very straight plane.
amorphous solids
- short range order; no consistent structure of atoms throughout the solid
- broad range of melting temperatures for any given amorphous solid, and they have irregular breakage patterns.
An unknown solution has its initial pH measured, is titrated, and the resulting analysis of the titration is shown below. Which of the following could be the compound in the original solution?
A. H2SO3
B. Ba(OH)2
C. H3PO4
D. CH3CO2H
E. NaOH
A
There are two humps - diprotic = two equivalence points!
Aqueous ammonium sulfide is added to a solution of iron (II) chloride. What are the spectator ions in this reaction?
I. NH4+
II. S2-
III. Cl–
IV. Fe2+
A. I and III
B. I and II
C. II and IV
D. III and IV
E. II and III
A
Generally, salts with ammonium will dissolve, and salts with chloride, bromide, or iodide will also dissolve. Another important rule is salts with nitrate ions (NO3–) are soluble too. However, iron sulfide (the product) is NOT soluble and will precipitate as a solid.
NH4+ + S2- + Fe2+ + Cl– → FeS + NH4+ + Cl–
From the above chemical reaction, we see that NH4+ and Cl– appear as both a reactant and product without participating in the chemical reaction. They are spectator ions.
The actual reaction that occurs is:
Fe2+ + S2- → FeS
Which of the following are the correct quantum numbers for the 13th electron in chlorine’s electron configuration?
A. 3, 0, -1, 1/2
B. 3, -1, 1, 1/2
C. 3, 1, -1, 1/2
D. 4, 2, -1, 1/2
E. 4, 0, 2, 1/2
C
n = energy level of the electron l = this identifies the shape of the orbital that the electron occupies. S orbital = 0, p orbital = 1, d orbital = 2, f orbital = 3. ml = this helps to identify the suborbital that is being occupied. This runs from –l to +l. ms = -1/2 if the electron is spinning down; 1/2 if the electron is spinning up
The 13th electron of chlorine’s electron configuration is in the last suborbital of the p orbital, spinning upwards. Assigning the numbers as described results in the quantum numbers 3, 1, -1, 1/2.
A 1.0 L sample of an aqueous solution contains 0.20 mol of NaCl and 0.10 mol of MgCl2. What is the minimum amount of moles of AgNO3 that must be added to the solution to precipitate all of the Cl– ions as AgCl(s)?
A. 0.10 mol
B. 0.20 mol
C. 0.30 mol
D. 0.40 mol
E. 0.50 mol
D
In this problem, we assume that all of the Cl– dissociates in NaCl and MgCl2. Since NaCl only has one chlorine atom, when it dissociates it will produce 0.20 mol of Cl–. Since MgCl2 has 2 chlorines, it will produce 0.20 mol of Cl– (0.10 mol x 2 mol of Cl–). In total, we will have 0.40 mol of Cl– in the solution. Since there is only one silver atom in AgNO3, we will need 0.40 mol of Ag to react with all 0.40 mol of Cl–.
Colligative properties are properties of a solution that are determined by only the _______ of a solute in a solvent, and do not depend on the identity of the actual solute.
That means it doesn’t matter if you have NaCl or KBr, it only matters how many_____ of _____ is in the solvent.
What method is used to measure the weights of polymers by using osmotic pressure?
concentration, particles of solute
Berkely-Harley
Which of the following is the most likely formed compound between atoms X and Y?
Atom X: 1s22s22p63s2
Atom Y: 1s22s22p4
A. X3Y
B. X2Y
C. X2Y3
D. XY
E. XY2
D
Using the periodic table, we can find that atom X is magnesium and atom Y is oxygen.
These atoms are most often found in with a +2 and -2 charge in compounds, respectively.
Therefore, we only need one of each atom to form the likely compound MgO, or magnesium oxide.
In distillation, the evaporated compound will be collected on a:
a) filter flask
b) buret
c) condenser
d) pipet
the mixture is boiled, until one of the compounds evaporates.
The evaporated compound is then immediately cooled through the condenser and collected on the other end in a flask.
Combustion formula
CxHx + O2 > CO2 + H2O
Which of the following descriptions is correct regarding nitrogen and phosphorus?
A. Nitrogen has a larger atomic radius than phosphorus
B. Nitrogen is a metalloid and phosphorus is a nonmetal
C. Nitrogen can bond to fewer atoms than phosphorus
D. Nitrogen is less electronegative than phosphorus
E. Nitrogen less readily forms π bonds than phosphorus
C
Nitrogen, being on top of phosphorus, and containing fewer electrons has a smaller atomic radius than phosphorus. Because of its smaller size, nitrogen can bond to fewer atoms than phosphorus.
In addition, because of the smaller size of nitrogen, it can approach another nitrogen atom more closely. As a result, formation of π bonds is more effective in nitrogen than in phosphorus.
Define the following terms:
isenthalpic
isobaric
adiabatic
isothermal
isentropic
isenthalpic = no change in enthalpy
isobaric = no change in pressure
adiabatic = no change in heat
isothermal = no change in temperature
isentropic = no change in entropy
Which of the following molecules has a net nonzero dipole moment?
A. CCl4
B. CO2
C. PCl5
D. PF3
E. BF3
D
For a molecule to have a net nonzero dipole moment, it has to have polar bonds and asymmetrical shape. All the given molecules have polar bonds, but only PF3 has an asymmetrical shape and therefore would have a net nonzero dipole moment.
The standard enthalpy of formation of liquid methanol is provided below,
C(graphite) + 2H2(g) + 1⁄2O(g)2–> CH3(l)OH ΔHf = -239 kJ
Which of the following would most likely be the value of the standard enthalpy of formation of gaseous methanol?
A. -412 kJ
B. -278 kJ
C. -239 kJ
D. -200 kJ
D
To go from a liquid to a gas requires an input of energy (endothermic, ΔH = +ve).
Therefore, we would expect a gas to have a more positive (less negative) ΔH than a liquid, as more energy is involved (ie. less energy is released).
This makes [D] our answer choice, as it is the only answer choice where ΔHf for the gas is more positive than the ΔH f we were provided for the liquid.
An unknown gas has a density of 1.79 g•L-1 at 273K and 1 atm. Identify the gas.
A. He
B. Ne
C. Ar
D. Kr
E. Xe
C
All you need to know is that there is 1 mol in 22.4L at STP, which is 273K (0° Celsius) and 1 atm.
Commit 22.4L in 1 mol of gas at STP to memory, it’ll help you out a lot on the DAT. From this information you can find the molar mass of the gas, which will reveal the identity of the gas.
Raoult’s law tells us that the ____ _____ of a solution is equal to the vapor pressure of the ____ ____ multiplied by the mole _____ of the ____
vapor pressure, pure solvent, fraction, solvent
A given substance has a boiling point of 177oC, and a molar heat of condensation of -90 kJ/mol. What is the molar entropy of condensation of the substance?
A. – 200 J/mol K
B. – 24 J/mol K
C. 133 J/mol K
D. 283 J/mol K
E. 339 J/mol K
A
Consider the following reduction half-reactions:
Which of the following is the Eº cell for the reduction of chlorine?
A. -0.28 + 1.36
B. -0.28 + -1.36
C. -1.36
D. 0.28
E. 0.28 + 1.36
Incorrect
E
Plot for zero order
A student measures the mass of a compound to be 9.01 g and its volume to be 11.0 mL. What is the density in g/mL?
A. 0.8
B. 0.82
C. 0.819
D. 0.8191
E. 0.81909
C
We have 3 significant figures in 9.01g and 3 significant figures in 11.0mL, so our answer must have 3 significant figures.
What is the mass percent of methanol in a solution prepared by diluting 16 grams of methanol with 32 grams of water?
A. 8%
B. 16%
C. 25%
D. 33%
E. 50%
D
Combustion analysis of a sample compound containing only C and H determines there was 18 g of C and 1 g of H in the sample. What is the empirical formula of this compound?
A. C2H2
B. C3H2
C. CH3
D. C1.5H
E. C2H3
B
**understand why!!*
What is liquid column chromatography used for?
Liquid column chromatography is used to differentiate liquids in a solution on the basis of differences in polarity
The preferred colligative property for measuring the molecular weight of polymers is osmotic pressure. Which of the following best explains why osmotic pressure is preferred to measure the molecular weight of polymers?
A. Small changes are easier to measure in osmotic pressure than in other colligative properties.
B. Polymers cannot pass through the semi-permeable membrane, but simple salts can.
C. Osmotic pressure measures the concentration of solute in molarity instead of molality.
D. The changing temperature of the solution needed for measuring other colligative properties changes the number of solute particles in solution.
E. Other colligative properties are more sensitive to solute concentration than osmotic pressure.
A
In order to be a spontaneous reacton, the reduction potential of the cathode must be (lesser/greater) than the reduction potential of the anode
greater
Which elements react in the presence of pure oxygen?
Know for the DAT that 1A alkali metals and 2A alkaline earth metals react in the presence of pure oxygen.
Sodium and the group 1A metals will react violently with pure oxygen. The reactions are normally combustions.
Group 2A metals also react with oxygen, but not to the extent of the 1A elements.
Germanium, sulfur, and boron react with oxygen to make oxides.
A student is examining a crystalline solid. Which of the following findings would be most expected during analysis of this substance?
A. Short range order of atoms
B. Sharp, well defined melting temperature
C. Malleable shape deformation
D. Random lattice structure
E. Irregular breakage patterns
B
In a zero order reaction, the half life ____ as the concentration _____
In a first order reaction, the half life is _____ and ______ of the concentration
Which types of reactions will resemble each other in a plot?
In second order reactions, the concentration will _____ quickly and the half life will _____ as the concentration _____
zero order = decreases, decreases
first order = constant, independent
first and second will look similar in a plot
second order = decrease, increase, decrease
[C] is the correct answer. Looking at trials 1 and 2, the table shows that increasing the concentration of B has no effect on the rate of the reaction.
So the rate law does not depend on B. But looking at trials 1 and 3, doubling the concentration of A doubles the rate.
Thus, B is zero order and A is first order, resulting in the rate equation shown by answer [C].
How many grams of oxygen are needed to completely react with 0.50 moles of C3H8 (58 g/mol)?
A. 12 g
B. 20 g
C. 80 g
D. 160 g
E. 400 g
C
Plot for first order
E
An acid is defined as a proton donor, and a base is defined as a proton acceptor. In the first reaction, we see that water accepts a proton to form H3O+, thus acting as a base. In the second reaction we see that water donates a proton to form H2, and thus acts as an acid. This fits answer E.
1 mol of HNO3 is dissolved in 54.0 grams of H2O. What is the mole fraction of HNO3?
A. 0.25
B. 0.33
C. 0.66
D. 0.75
E. 1.0
A
Calculate the standard cell potential of a voltaic cell based on the following half-reactions.
A. –0.416 V
B. –0.144 V
C. +0.144 V
D. +0.281 V
E. +0.416 V
What is the mole fraction of HNO3 in a 64% (w/w) aqueous solution of HNO3?
What is the temperature at which 64 g of O2 will occupy a volume of 8.2 L at 760 Torr?
A. 5.00 K
B. 50.0 K
C. 100 K
D. 500 K
E. 1.00 × 103 K
B
The melting point of ionic compounds _______ charge and ______ size according to which law?
a) increasing, increasing,
b) decreasing, increasing
c) decreasing, decreasing,
d) increasing, decreasing
D - coulombs law
Where does melting and boiling occur on the diagram?
melting occurs across the solid-liquid line
vaporization (ie. boiling) occurs across the liquid-gas line.
Gibbs Free Energy Chart
Calculate the heat of enthalpy, ΔHo for the following reaction, based on the bond energies provided:
CH4(g) + 4Cl2(g) → 4HCl(g) + CCl4(g)
Bond energies:
C–H = 413 kJ / mol Cl–Cl = 243 kJ / mol H–Cl = 432 kJ / mol C–Cl = 330 kJ /mol
A. [1(413) + 4(243)] + [4(432) + 1(330)]
B. (413 + 243) - (432 + 330)
C. [4(413) + 4(243)] - [4(432) + 4(330)]
D. [1(413) + 4(243)] - [4(432) + 1(330)]
E. (413 + 243) - (432 + 330)
C
For the reaction 2NO(g) + O2(g) → 2NO2(g), the concentration of NO was monitored from 0 to 100 seconds. Given the following data, what is the average rate of disappearance of NO from 0 to 100 seconds?
A. 5.0 × 10–4 M/s
B. 2.5 × 10–6 M/s
C. 1.0 × 10–5 M/s
D. 5.0 × 10–6 M/s
E. 2.5 × 10–3 M/s
A particular compound has a formula NaClOx where x is unknown. If the compound contains 33.3% Cl, what is the formula of the compound?
A. NaClO molar mass: 74.4 g / mol
B. NaClO2 molar mass: 90.4 g / mol
C. NaClO3 molar mass: 106.4 g / mol
D. NaClO4 molar mass: 122.4 g / mol
E. NaClO5 molar mass: 138.4 g / mol
What is the concentration in molarity of a 25% (w/w) solution of HClO4 (MM = 100.46 g/mol) that has a density of 1.5 g/mL?
A. 1.50 M
B. 3.75 M
C. 25.0 M
D. 40.0 M
E. 66.6 M
B
An aqueous solution of 0.75 M glucose has an osmotic pressure of 2.4 atm at 300 K. If the osmotic pressure is doubled, and the temperature were tripled, what would be the molarity of the resulting solution?
A. 0.50 M
B. 1.5 M
C. 4.5 M
D. 7.5 M
E. 15 M
A
C. rate = k[NO]2[H2]
Changing the concentration of H2 from 0.50 to 0.25 (decreased by half, from Exp 1 and 2) at constant NO concentration also decreased the rate by half. This indicates that the reaction is first order with respect to H2. Doubling the concentration of NO at constant H2 concentration (Exp 1 and 3) increases the rate by a factor of four. This indicates that order of the reaction with respect to NO is two. Thus, the rate law is:
Rate = k[NO]2[H2]
Common Bond Angle Chart
