chem study guide final

Based on the thermodynamic data, which of the following is true at 298 K? A. Keq= 0 B. 0 < Keq < 1 C. Keq = 1 D. Keq > 1

0<Keq<1

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? A. K+ + Cl- ->KCl B. HNO2 -> H+ + NO2- C. H+ + OH- -> H2O D. H+ + NO2- -> HNO2

H+(aq)+NO2-(aq)->HNO2(aq)

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. A. H positive S positive, pos and pos, neg and neg B. H pos S pos, pos and pos, neg and pos C. H neg S neg, neg and neg, pos and pos D. H neg S pos, neg and pos, and pos and neg

(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 A. H < 0 because energy is released when N-N bond breaks B. H < 0 because energy is required to break N-N bond C. H > 0 because energy is released when N-N bond breaks D. H > 0 because energy is required to break N-N bond

(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? A. -93 kJ B. -121 kJ C. -186 kJ D. -242 kJ

-93 kJ

(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? A. 200 kj/mol B. 300 kj/mol C. 400 kj/mol D. 500 kj/mol

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? A. 16% B. 32% C. 64% D. 96%

32%

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? A. N, H, F, B in the middle surrounded by H and F B. N, H, B in the middle surrounded by H and F C. N, F, and B in the middle surrounded by H and F D. N and B in the middle surrounded by H and F

ALL ANSWERS ARE DIAGRAMS. Chose the one with N and B in the middle, surrounded by H and F

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? A. Acid Strength= HClO2<HCOOH Base Strength=ClO2-<HCOO- B. Acid Strength= HClO2<HCOOH Base Strength=ClO2->HCOO- C. Acid Strength= HClO2>HCOOH Base Strength=ClO2->HCOO- D. Acid Strength= HClO2>HCOOH Base Strength=ClO2-<HCOO-

Acid Strength= HClO2>HCOOH Base Strength=ClO2-<HCOO-

In the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs? A. Before= sp After+ sp2 B. Before=sp After sp3 C. Before= sp2 After sp D. Before=sp2 After sp3

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? A. BCl3 B. CH4 C. CBr4 D. PbCl2

CBr4

2H2O2(l)->2H2O(l)+O2(g) The exothermic process represented above is best classified as a A. physical change because a new phase appears in the product B. physical change because O2 that was dissolved comes out of solution C. chemical change because entropy increases as the process proceeds D. chemical change because covalent bonds are broken and new covalent bonds are formed

Chemical change because covalent bonds are broken and new covalent bonds are formed

(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? A. E= 1.63 G= -157 B. E= 1.63 G= -944 C. E= 5.63 G= -543 D. E= 5.63 G= -3262

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? A. X has a greater electronegativity than Y B. X has a greater ionization energy than Y C. Element Y has a greater nuclear charge than element X D. Isotopes of element Y are equal in abundance but element X is not

Element Y has a greater nuclear charge than element X does.

Which of the following has the bonds arranged in order of decreasing polarity? A. H-F > N-F > F-F B. H-I > H-Br > H-F C. O-n > O-S > O-Te D. Sb-I > Sb-Te > Sb-Cl

H-F>N-F>F-F

Ne, HF, C2H6, CH4 Which of the substances listed above has the highest boiling point, and why? A. Ne because atoms have largest radius B. HF because from hydrogen bonds C. C2H6 because it can form multiple hydrogen bonds D. CH4 because its molecules have the greatest LDF

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? A. Bronsted Lowry acid base reaction because the solution is neutral at the end B. Bronsted-Lowry acid base reaction because HNO3 is a strong acid C. Redox reaction because Cu is oxidized and H+ is reduced D. Redox reaction because Cu is oxidized and nitrogen atom in No3- is reduced

It is a redox reaction, because Cu(s) is oxidized and the nitrogen atom in NO3-(aq) is reduced

(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⁺ A. K= (K1)(Ka)(Kw) B. K= (K1)(Ka)/Kw C. K=K1/(Ka)(Kw) D. K= (K1)(Kw)/Ka

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? A. Mg) does not contain free electrons, but MgO contains free electron that can flow. B. Mg0 contains no water, but MgO contains water that can conduct conductivity C. Mg) consists of separate Mg2+ ions and O2- ions but MgO contains MgO molecules that can conduct electricity D. 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.

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. A. CH4 B. CCl4 C. NH3 D. PH3

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? A. PNO2 will decrease and PN2O4 will increase B. PNO2 will increase and PN2O4 will decrease C. Both PNO2 and PN2O4 will decrease D. No change will take place

No change will take place

The ideal gas law best describes the properties of which of the following gases at 0C and 1 atm? A. PH3 B. HBR C. SO2 D. N2

N₂

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. A. 2O3 slow B. O3 slow NO2 fast C. NO2 slow NO fast D. NO2 slow NO fast

O3(g)+NO(g)->NO2(g)+O2(g) slow NO2(g)+O(g)->NO(g)+O2(g) Fast

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? A. Rate=k [NO2] [CO] B. Rate=k [NO2]^2 C. Rate=k [NO3] [CO] D. Rate=k [NO2] [NO3] [CO]

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 A. Reaction A B. Reaction B C. Reaction C D. Reaction D

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 A. SO3 B. SO4 C. S2O6 D. S2O8

SO₃

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? A. Examining the crystals B. Determining density of substance C. Testing the electrical conductivity of the crystals D. Testing the electrical conductivity of an aqueous solution

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. A. forward reaction is exothermic B. forward reaction is endothermic C. ice bath lowered activation energy D. ice bath raised activation energy

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? A. activation energy of the reaction will increase B. activation energy of the reaction will decrease C. frequency of collisions between H+ and ions and ClO- ions will increase D. value of rate constant will increase

The frequency of collisions between H+(aq) ions and ClO- (aq) ions will increase.

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? A reaction is not thermo favorable at 25 B. H for reaction has a large positive value at 25 C. S has a large negative value at 25 D. has a large activation energy at 25C

The reaction has a large activation energy at 25C

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? A. Sample contains only NaCl B. Sample contains NaCl and NaI C. Sample contains NaCl and KCl D. Sample contains NaCl and LiCL

The sample contains NaCl(s) and LiCl(s)

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? A. metal pieces much smaller than others B. heated the reaction mixture as HNO3 was added C. used a 1.5 M solution instead of a 15.8 M solution D. used 3 g sample instead of 2 g sample

The students used a 1.5 M solution of HNO3(aq) instead of 15.8 M solution of HNO3(aq)

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? A. activation energy for Step 1 is large and positive B. activation energy for Step 2 is small and pos C. value of S is small and pos D. value of H is large and neg

The value of (delta) H for the overall reaction is large and negative

(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+]? A. X < Z < Y B. Y < X < Z C. Z < Y < X D. Z < X < Y

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? A. Y B. Zr C. Nb D. Th

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 A. forces among Br2 molecules are stronger than those among Cl2 molecules B. forces among Cl2 molecules are stronger than Cl-Cl bond C. Br-Br bond is stronger than the Cl-Cl bond D. Cl-Cl bond is stronger than Br-Br bond

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)? A. .44 atm B. 2.0 atm C. 2.3 atm D. 4.0 atm

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. A. 0.5 atm B. 1.0 atm C. 2.5 atm D. 4.0 atm

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 A. 22.0 C B. 24.7C C. 25.3C D. 28.0C

24.7C

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.) A. 4 x 10^-4 mol B. 3 x 10^-4 mol C. 4 x 10^-6 mol D. 3 x 10^-6 mol

4 x 10⁻⁶

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? A. 6 H202 and 4 Mn2+ B. 4, H2O2, 3 Mn2+, and 3 MnO4 C. 5 H2O2 and 2 Mn2+ D. 5 H2O2, 1 Mn2+, and 1 MnO4

ALL ANSWERS ARE IMAGES Correct image has 5 H2O2 and, 2 Mn2+

(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=? A. Ag+ because Keq3=4 B. Ag+ because Keq1 < Keq2 C. Ag(NH3)2 because Keq3= 1.6x10^7 D. Ag(NH3)2 because Keq1 < Keq2

Ag(NH3)2⁺(aq), because Keq3=1.6x107

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) A. Cl + Mg+ -> Cl+ + Mg B. Al + Mg+ -> Al+ + Mg C. P + Mg+ -> P+ + Mg D. S + Mg+ -> S+ + Mg

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? A. 4 of 3 B. 4 of 3 and 1 of 2 C. 2 of 3 atoms together and 4 of two D. 7 of 3 atoms togethers

All answers are pictures. Chose the one that has 4 of 3 atoms together and 1 of 2 atoms together

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? A. Compound 1 because it has stronger dipole dipole forces B. Compound 1 because it form hydrogen bonds C. Compound 2 because less polarizable and weaker LDFs D. Compound 2 because it forms hydrogen bonds and compound 1 doesn't

Compound 2, because it forms hydrogen bonds, whereas compound 1 does not.

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? A. only favored at high temperature B. only favored at low temperature C. favored at all temperature D. not favored at any temperature

It is not favored at any temperature

(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? A. Element carbon is harder than elemental iron B. additional carbon atoms within the alloy make the high-carbon C. additional carbon atoms within alloys increase D. additional carbon atoms within the alloy make it more difficult

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? A. O3 will increase because Q < Kc B. O3 will decrease because Q < Kc C. O3 will increase because Q > Kc D. O3 will decrease becase Q > Kc

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? A. mixture will become more orange because OH- will oxidize B. mixture will become more yellow because OH- will reduce Cr C. mixture will become more yellow because OH will shift equilibrium toward products D. mixture will not change

The mixture will become more yellow because OH-(aq) will shift the equilibrium toward products

(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? A. Cu(NO3)2 not diluted properly B. spectrophotometer calibrated with tap water C. student labeled cuvettes incorrectly D. spectrophotometer was originally set to appropriate wavelength

The student labelled the cuvettes incorrectly, reversing the labels on two of the solutions of known concentrations