2. 0. 1. 7 ye
The process of dissolution of NaCl(s) in H2O(l) is represented in the diagram above. Which of the following summarizes the signs of (delta)H and (delta)S for each part of the dissolution process.
(ANSWERS ARE IN A TABLE) Positive for both H and S in solvent-solvent and solute-solute. Neg for both H and S in solute solvent interactions
Which of the following statements about (delta)H for the reaction is correct
(delta)H>0 because energy is required to break the N-N bond
What is the value of the enthalpy change per mole of HCl(g) produced?
-93 kJ
Based on the thermodynamic data, which of the following is true at 298 K?
0<Keq<1
(BOND ENERGIES ARE GIVEN) Based on the bond energies listed in the table above, which of the following is closest to the bond energy of the C-N bond?
300 kJ/mol
The students determined that the reaction produced 0.010 mol of Cu(NO3)2. Based on the measurement, what has the percent of Cu by mass in the original 2.00 g sample of the mixture?
32%
Fe³⁺ (aq) +KSCN(s)->FeSCN²⁺(aq)+K⁺(aq) To determine the moles of Fe3+(aq) in a 100mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe3+(aq) into the dark red species, FeSCN2+(aq), as represented by the equation above. The absorbance of FeSCN2+(aq) a different concentration is shown in the graph to the right. (IMAGE) If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe3+(aq) were present in the 100 mL sample?(Assume that any volume change due to adding the KSCN(s) is negligible.)
4 x 10⁻⁶
On the basis of the pH curve, the pKa value of the acid is closest to
5
NH3 reacts with BF3 to form a single species. Which of the following structural diagrams is the most likely representation of the product of the reaction?
ALL ANSWERS ARE DIAGRAMS. Chose the one with N and B in the middle, surrounded by H and F
A particle view of a sample of H2O2(aq) is shown to the right. The H2O2(aq) is titrated with KMnO4(aq), as represented by the equation below. (IMAGE AND EQUATION IM TOO LAZY TO TYPE) Which of the following particle views best represents the mixture when the titration is halfway to the equivalence point?
ALL ANSWERS ARE IMAGES Correct image has 5 H2O2 and, 2 Mn2+
An acetate buffer solution is prepared by combining 50 mL of 0.20 M acetic acid, HC2H3O2(aq), and 50 mL and 0.20 M sodium acetate, NaC2H3O2(aq). A 5.0 mL sample of 0.1 M NaOH(aq) is added to the buffer solution. Which is the following is a correct pairing of the acetate species present in greater concentration and the pH of the solution after the NaOH(aq) is added?
Acetate Species=C2H3O2- pH=>4.7
In the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs?
Before=sp² After= sp³
The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of periodic properties, which of the following compounds can most likely be used as a fire resistant chemical?
CBr4
2H2O2(l)->2H2O(l)+O2(g) The exothermic process represented above is best classified as a
Chemical change because covalent bonds are broken and new covalent bonds are formed
Based on structures shown above, (IMAGE) which of the following statements identifies the compound with the highest boiling point and provides the best explanation for the higher boiling point?
Compound 2, because it forms hydrogen bonds, whereas compound 1 does not.
Mg(OH)2(s)<->Mg²⁺(aq) +2OH⁻(aq) The exothermic dissolution of Mg(OH)2(s) in water is represented by the equation above. The Ksp of Mg(OH)2 is 1.8E-11. Which of the following changes will increase the solubility of Mg(OH)2 in an aqueous solution?
Decreasing the pH
(Half reactions are given) Based on the formation in the table above, which of the following shows that the cell potential and Gibbs free energy change for the overall reaction that occurs in a standard galvanic cell?
E=+1.63 G=-944
The complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. (IMAGE) Which of the following can be inferred from the data?
Element Y has a greater nuclear charge than element X does.
A student prepares a solution by combining 100 mL of 0.30 M HNO3(aq) and 100 mL of 0,30 M KNO2(aq). Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1.0 M HCl(aq) does not significantly change the pH of the solution?
H+(aq)+NO2-(aq)->HNO2(aq)
Which of the following has the bonds arranged in order of decreasing polarity?
H-F>N-F>F-F
Ne, HF, C2H6, CH4 Which of the substances listed above has the highest boiling point, and why?
HF, because its molecules form hydrogen bonds
Cu(S)+ 4HNO3(aq)-->Cu(NO3)2(aq)+2NO2(g)+2H2O(l) Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3 (aq) into their beakers. the reaction between the copper in the mixture and the HNO3(aq) is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indication the formation of Cu2+(aq). The solutions were then diluted with distilled water to known volumes. Which of the following is true about the reaction?
It is a redox reaction, because Cu(s) is oxidized and the nitrogen atom in NO3-(aq) is reduced
Two molecules of the amino acid glycine join through the formation of a peptide bond, as shown above. The thermodynamic data for the reaction are listed in the following table (IMAGE AND TABLE) Under which of the following temperature conditions is the reaction thermodynamically favored?
It is not favored at any temperature
(REACTION TABLE WITH Keq GIVEN) Based on the information above, which of the following expressions represents the equilibrium constant, K, for the reaction represented by the equation below? La³⁺+CO₃²⁻<-> LaCO₃⁺
K=(K1)(Kw)/Ka
Based on the diagram above, which of the following best helps to explain why MgO(s) is not able to conduct electricity, but MgO(l) is a good conductor of electricity?
MgO(s) consists of separate Mg2+ ions and O2- ions held in a fixed lattice, but in MgO(l) the ions are free to move and conduct electricity.
On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water.
NH3
Which of the following best predicts how the partial pressures of the reacting species will be affected if a small amount of Ar(g) is added to the equilibrium mixture at constant volume?
No change will take place
The ideal gas law best describes the properties of which of the following gases at 0C and 1 atm?
N₂
NO2(g)+CO(g)->NO(g)+CO2(g) The reaction between NO2(g) and CO(g) is represented above. The elementary steps of a proposed mechanism are represented below. Step 1: 2NO2(g)-> NO(g) _NO3(g) Slow Step 2: NO3(g) +CO(g)->NO2(g)+CO2(g) fast Which of the following is the rate law for the overall reaction that is consistent with the proposed mechanism?
Rate=k[NO2]2
(4 reactions are given, A-D) The reactions represented above are carried out in sealed, rigid container and allowed to reach equilibrium. If the volume of each container is reduced from 1.0 L to .5 L at constant temperature, for which of the reactions will the amount of products be increased
Reaction A
If a pure sample of an oxide of sulfur contains 40 percent sulfur and 60 percent oxygen by mass, then the empirical formula of the oxide is
SO₃
What will be the effect on the amount of gas produced if the experiment is repeated using 0.35g of K(s) instead of 0.35 g of Li(s)?
Some gas will be produced but less than the amount of gas produced with Li(s)
A student is given a sample of a pure, white crystalline substance. Which of the following would be most useful in providing data to determine if the substance is an ionic compound?
Testing the electrical conductivity of an aqueous solution of the substance
Which of the following statements best helps to explain why the contents of the tube containing the equilibrium mixture turned a lighter color when the tube was placed into an ice bath.
The forward reaction is endothermic
Cl-(aq)+CLO-(aq)+2H(aw)->CL2(g) +H2O(l) What effect will increasing [H+] at constant temp have on the reaction represented above?
The frequency of collisions between H+(aq) ions and ClO- (aq) ions will increase.
2XY(g)<->X2(g)+Y2(g) Kp=230 A certain gas, XY(g), decomposes as represented by the equation above. A sample of each of the three gases is put in the three gases is put in a previously evacuated container. The initial partial pressures of the gases are shown in the table below. (TABLE) The temperature of the reaction mixture is held constant. In which direction will the reaction proceed?
The reaction will form more reactant
A sample of a solid labeled as NaCL may be impure. A student analyzes the sample and determines that it contains 75 percent chlorine by mass. Pure NaCl(s) contains 61 percent chlorine by mass. Which of the following statements is consistent with the data?
The sample contains NaCl(s) and LiCl(s)
H2(g)+Cl2(g)<->2HCl(g) Kp=2E30 at 298 K HCl(g) can be synthesized from H2(g) and Cl2(g) as represented above. A student studying the kinetics of the reaction proposes the following mechanism. (3 steps listed out, too tired to type them, sorry) Which of the following statements identifies the greatest single reason that the value of Kp for the overall reaction at 298 K has such a large magnitude?
The value of (delta) H for the overall reaction is large and negative
Benzene, C6H6, has the structure shown above. Considering the observation that benzene is only sparingly soluble in water, which of the following best described the intermolecular forces of attraction between water and benzene?
There are dipole-induced dipole and london dispersion interactions between water and benzene
(ANOTHER TABLE GIVEN) Three saturated solutions (X,Y, and Z) are prepared at 25C. Based on the information in the table above, which of the following lists the solutions in order of increasing [Ag+]?
Z<X<Y
(IMAGE) The mass spectrum of an average sample of a pure element is shown in the figure above. Which of the following is the identity of the element?
Zr
At 298 k and 1 atm, Br₂ is a liquid with a high vapor pressure, and Cl₂ is a gas. Those observations provide evidence that under the given conditions, the
forces among Br₂ molecules are stronger than those among Cl₂ molecules
N2O4(g)<-> 2NO2 Kp=3.0 at 70C colorless brown A mixture of NO2(g) and N2O4(g) is placed in a glass tube and allowed to reach equilibrium at 70C, as represented above. If P(N2O4) is 1.33 atm when the system is at equilibrium at 70C which is P(NO2)?
2.0 atm
When the 4.0L of He(g), 6.0 L of N₂(g) and 10 L of Ar(g), all at 0C and 1 atm, are pumped into an evacuated 8.0L rigid container, the final pressure in the container is 0C.
2.5 atm
When the 5.0g of NH4ClO4(d) is added to 100 mL of water in a calorimeter, the temperature of the solution formed decreases by 3.0C. If 5.0g of NH4ClO4(s) is added to 1000 mL of water in calorimeter initially at 25C, the final temperature of the solution will be approximately
24.7C
Which of the following is the balanced net ionic equation for the reaction between Li(s) and water?
2Li(s)+2H2O(l)->2Li+(aq)+2OH-(aq)+H2(g)
ClO2-(aq)+HCOOH(aq)<-> HClO2(aq)+HCOO-(aq) Keq<1 What are the relative strengths of the acids and bases in the reaction represented by the equation above?
Acid Strength= HClO2>HCOOH Base Strength=ClO2-<HCOO-
(2 equations given with Keq) Equal volumes of 0.1 M AgNO3(aq) and 2.0 M NH3(aq) are mixed and the reactions represented above occur, which Ag species will have the highest concentration in the equilibrium system shown below and why? Ag⁺(aq)+2NH3(aq)<-> Ag(NH3)2⁺(aq) Keq3=?
Ag(NH3)2⁺(aq), because Keq3=1.6E7
The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of the element (i.e. X(g)--> (X^+(g)+e-). The values of the first ionization energies for the third row elements are shown in the graph above. On the basis of the information give, which of the following reactions is exothermic? (IMAGE)
Al(g)+Mg+(g)->Al+(g)+Mg(g)
A mixture of CO(g) and O2 (g) is placed in a container, as shown above. A reaction occurs, forming CO2(g). Which of the following best represents the contents of the box after the reaction has proceeded as completely as possible?
All answers are pictures. Chose the one that has 4 of 3 atoms together and 1 of 2 atoms together
(DIAGRAM) Which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented above?
Hydrogen Bond
O3(g)+O(g)->2O2(g) The decomposition of O3(g) in the upper atmosphere is represented by the equation above. The potential energy diagram for the decomposition of O3(g) in the presence and absence of NO(g) is given below. (IMAGE) Which of the following mechanisms for the catalyzed reaction is consistent with the equation and diagram above.
O3(g)+NO(g)->NO2(g)+O2(g) slow NO2(g)+O(g)->NO(g)+O2(g) Fast
(TABLE ) Acid dissociation constants of two acids are listed in the table above. A 20 mL sample of a 0.1 M solution of each acid is titrated to equivalence point with 20 mL of 0.1 M NaOH. Which of the following is a true statement about the pH of the solutions at the equivalence point?
Solution 1 has a higher pH at the equivalence point because CH3CO2H has a stronger conjugate base.
(Table shoes type of steel and characteristics) The table above provides some information about two types of steel, both of which are alloys of iron and carbon. Which of the following best helps to explain why high-carbon steel is more rigid than low carbon steel?
The additional carbon atoms within the allow make it more difficult for the iron atoms to slide past one another.
3O2(g)<->2O3(g) Kc=1.8E-56 at 570 K For the system represented above, [O2] and [O3] initially are 0.150 mol/L and 2.5 mol/L respectively. which of the following best predicts what will occur as the system approaches equilibrium at 570 K?
The amount of O3(g) will decrease, because Q>Kc
Cr2O7² ⁻(aq) + H2O (l)<->2CrO4² ⁻(aq)+2H3O+(aq) orange yellow The equilibrium system represented by the equation above initially contains equal concentrations of Cr2O7² ⁻(aq) and 2CrO4² ⁻(aq). Which of the following statements correctly predicts the result of adding a sample of 6.0 M NaOH(aq) to the system and provides an explanation?
The mixture will become more yellow because OH-(aq) will shift the equilibrium toward products
2H2(g)+O2(g)->H2O(g) When H2(g) and O2(g) are mixed together in a rigid reaction vessel at 25C, no reaction occurs. When the mixture is sparked, however, the gases react vigorously according to the equation above, releasing heat. Which of the following statements correctly explains why the spark is needed for the reaction to occur when the gases are originally at 25C?
The reaction has a large activation energy at 25C
(TABLE) To determine the number of moles of Cu in the sample of the mixture, the students measured the absorbance of known concentrations of Cu(NO3)2(aq) using a spectrophotometer. A cuvette filled with some of the solution produced from the sample was also tested. The data recorded by one student are shown in the table above, on the basis of the data provided, which of the following is a possible error that the student made?
The student labelled the cuvettes incorrectly, reversing the labels on two of the solutions of known concentrations
In one student's experiment the reaction proceeded at a much slower rate than it did in the other students' experiments. Which of the following could explain the slower reaction rate?
The students used a 1.5 M solution of HNO3(aq) instead of 15.8 M solution of HNO3(aq)
A 0.35g Sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all the Li(s) has reacted with H2O(l), the solution in the flask is added to a clean, dry buret, and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below. Which of the following changes will most likely increase the rate of reaction between Li(s) and water?
Using a 0.35g sample of Li(S) cut into small peices
