AP Classroom - AP Chemistry Units 1-4 and Unit 6 quizzes

(1.1) Which of the following numerical expressions gives the number of particles in 2.0g of Ne?

(2.0g/20.18 g/mole)(6.0x10^23 particles/mol)

(6.9) Based on the information for two different reactions given above, which of the following gives the quantities needed to calculate the enthalpy change for the reaction represented by the overall equation below? 2NO(g) + O2(g) → N2O4(g)

(−ΔH1) + ΔH2

(6.9) Based on the chemical equations and their associated enthalpy changes shown above, which of the following identifies the quantities needed to calculate ΔH°f, the standard enthalpy of formation of H2O(l), in kJ/mol?

(−ΔH°1) + 1/2(−ΔH°2) +(ΔH°3) + (ΔH°4)

(6.5) The diagram above represents the melting of H2O(s). A 2.00mole sample of H2O(s) at 0°C melted, producing H2O(l) at 0°C. Based on the diagram, which of the following best describes the amount of heat required for this process and the changes that took place at the molecular level?

12.0kJ of heat was absorbed to overcome some of the hydrogen bonding forces holding the water molecules in fixed positions in the crystalline structure.

(6.4) In an experiment to determine the specific heat of a metal, a student transferred a sample of the metal that was heated in boiling water into room-temperature water in an insulated cup. The student recorded the temperature of the water after thermal equilibrium was reached. The data are shown in the table above. Based on the data, what is the calculated heat q absorbed by the water reported with the appropriate number of significant figures?

1640J

(1.5) Which of the following is the ground-state electron configuration of the F− ion?

1s2-2s2-2p6

(1.5) Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

1s2-2s2-2p6-3s1

(1.6) The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum?

1s2-2s2-2p6-3s2-3p3

(1.5) Which of the following best represents the ground-state electron configuration for an atom of selenium?

1s2-2s2-2p6-3s2-3p6-4s2-3d10-4p4

(4.9) The half-reactions for the oxidation-reduction reaction between Al(s) and Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients?

2

(6.4) For an experiment, 50.0g of H2O was added to a coffee-cup calorimeter, as shown in the diagram above. The initial temperature of the H2O was 22.0°C, and it absorbed 300.J of heat from an object that was carefully placed inside the calorimeter. Assuming no heat is transferred to the surroundings, which of the following was the approximate temperature of the H2O after thermal equilibrium was reached? Assume that the specific heat capacity of H2O is 4.2J/(g⋅K).

23.4°C

(4.9) Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq) and Ni(s) based on the half-reactions represented above?

2Ag+(aq) + Ni(s) → 2Ag(s) + Ni2+(aq)

(1.4) A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?

3, 4, 6, 7

(6.7) An equation representing the dissociation of O2(g) and a table of bond enthalpies are shown above. Based on the information, which of the following is the enthalpy of dissociation for O2(g) ?

495kJ/mol

(3.12) A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510nm corresponds to an approximate frequency of 6×10^14 s−1. What is the approximate energy of one photon of this light?

4×10^−19 J

(3.12) The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10^−19 J. Which of the following is closest to the frequency of the light with photon energy of 3.3×10^−19 J?

5.0×10^14 s-1

(6.4) A student mixes 50mL of 1.0MHCl and 50mL of 1.0MNaOH in a coffee-cup calorimeter and observes the change in temperature until the mixture reaches thermal equilibrium. The initial and final temperatures (°C) of the mixture are shown in the diagram above of the laboratory setup. Based on the results, what is the change in temperature reported with the correct number of significant figures?

5.5°C

(4.1) A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure?

A cube of metal was changed into a flat sheet of metal.

(4.4) A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?

After the water has evaporated, the white crystals in the beaker have a mass of 20.0g

(6.1) For a classroom demonstration, a chemistry teacher puts samples of two different pure solid powders in a beaker. The teacher places the beaker on a small wooden board with a wet surface, then stirs the contents of the beaker. After a short time the students observe that the bottom of the beaker is frozen to the wood surface. The teacher asks the students to make a claim about the observation and to justify their claims. Which of the following is the best claim and justification based on the students' observation?

An endothermic chemical change occurred because the temperature of the beaker and the water on the board decreased as heat was absorbed by the reaction.

(1.8) If Na reacts with chlorine to form NaCl, which of the following elements reacts with Na to form an ionic compound in a one-to-one ratio, and why?

Br, because it has the same number of valence electrons as Cl.

(6.9) CS2(l)+2H2O(l)→CO2(g)+2H2S(g)ΔH°rxn=? Which of the following combinations represents the individual reactions and the quantities needed to determine ΔH° for the overall reaction represented by the chemical equation above?

CS2(l)+3O2(g)→CO2(g)+2SO2(g) ΔH°=−1075kJ 2H2O(l)+2SO2(g)→2H2S(g)+3O2(g) ΔH°=+1136kJ

(4.9) The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, which of the following identifies the oxidation and reduction half-reactions?

Chart with Oxidation Half Reaction as Cu(s) → Cu2+(aq) + 2 e- AND Reduction Half-Reaction as Ag+(aq) + e- → Ag (s)

(1.8) RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why?

CsCl, because its elements have very different electronegativities and it is an ionic compound

(3.9) A student performed a fractional distillation of a mixture of two straight-chain hydrocarbons, C7H16 and C8H18. Using four clean, dry flasks, the student collected the distillate over the volume ranges (A, B, C, and D) shown in the graph above. Over what volume range should the student collect the distillate of the compound with the stronger intermolecular forces?

D

(3.9) The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?

Decrease the percentage of ethyl acetate in the solvent.

(3.10) The survival of aquatic organisms depends on the small amount of O2 that dissolves in H2O. The diagrams above represent possible models to explain this phenomenon. Which diagram provides the better particle representation for the solubility of O2 in H2O, and why?

Diagram 2, because the polar H2O molecules can induce temporary dipoles on the electron clouds of O2 molecules.

(3.10) Based on their Lewis diagrams, which of the following pairs of liquids are most soluble in each other?

Diagram of C2H5OH and H20

(2.6) Which of the following Lewis diagrams best represents the bonding in the N2O molecule, considering formal charges?

Diagram with 2 N having triple bond with one single lone pair and N having single bond with O and 3 lone pairs

(2.3) The particle-level diagram above represents the structure of solid KF. Although the molar mass of KCl is greater than that of KF, the density of KCl is actually less than that of KF. Which of the following representations of the structure of KCl best helps to explain this phenomenon?

Diagram with 4 electrons and 5 protons, interchanging (A)

(4.7) The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?

Diagram with Na+ and NO3- as gases and Ag+ and Cl- solid at bottom

(2.7) Which of the following complete Lewis diagrams represents a molecule containing a bond angle that is closest to 120°?

Diagram with carbon atom having 2 O atoms and one C atom attached, surrounded by 3 domains

(3.9) A student obtains a liquid sample of green food coloring that is known to contain a mixture of two solid pigments, one blue and one yellow, dissolved in an aqueous solution of ethanol. Which of the following laboratory setups is most appropriate for the student to use in order to separate and collect a substantial sample of each of the two pigments?

Diagram with chromatography column (long pipet)

(3.5) The diagram above shows the distribution of speeds for a sample of N2(g) at 25°C. Which of the following graphs shows the distribution of speeds for a sample of O2(g) at 25°C (dashed line) ?

Diagram with dashed line taller and skinnier than bold line

(2.4) Copper atoms and zinc atoms have the same atomic radius, 135 picometers. Based on this information, which of the following diagrams best represents an alloy containing only copper and zinc atoms?

Diagram with grey and white dots with same size

(4.8) The particle diagram above represents an aqueous solution of a weak monoprotic acid. The white circles represent H atoms. Which of the following shows the species that act as a Brønsted-Lowry base and its conjugate acid, in that order, in the solution?

Diagram with large black circle with 2 small empty circles attached and one large black circle with 3 empty circles attached

(2.4) Steel is an alloy containing Fe atoms and C atoms. Which of the following diagrams best represents the particle-level structure of steel?

Diagram with large white dots as Fe and small grey dots as C

(4.2) Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?

F−(aq) + H+(aq) → HF(aq)

(1.2) The mass spectrum of the element Sb is most likely represented by which of the following?

Graph with amu lines at 121 and 123

(4.8) For the dissolution of HCl in water represented above, which of the following pairs includes the Brønsted-Lowry bases?

H2O(l) and Cl−(aq)

(3.10) A student places a piece of I2(s) in 50.0 mL of H2O(l), another piece of I2(s) of the same mass in 50.0 mL of C6H14(l), and shakes the mixtures. The results are shown above. What do the results indicate about the intermolecular interactions of the substances?

I2 and C6H14 have similar intermolecular interactions, and I2 and H2O do not.

(1.6) The complete photoelectron spectrum for an element is shown above. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?

In its compounds, the element tends to form ions with a charge of +1.

(2.6) The diagram above shows two resonance structures for a molecule of C6H6. The phenomenon shown in the diagram best supports which of the following claims about the bonding in C6H6 ?

In the C6H6 molecule, all the bonds between the carbon atoms have the same length.

(2.1) Two pure elements react to form a compound. One element is an alkali metal, X, and the other element is a halogen, Z. Which of the following is the most valid scientific claim that can be made about the compound?

It contains ionic bonds.

(2.3) Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?

It does not conduct electricity because its ions cannot move freely within the solid.

(3.1) The diagram above is a molecular model of a gaseous diatomic element that is just above its boiling point. Intermolecular forces between the gas molecules will cause them to condense into the liquid phase if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon?

It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.

(1.1) A student has 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?

KBr < KCl < NaCl

(3.1) The electron cloud of HF is smaller than that of F2 , however, HFHF has a much higher boiling point than F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF?

Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

(4.4) The table above summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and X were mixed?

Measuring the electrical conductivities of X and the mixture of water and X

(1.2) The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26amu represents an isotope of which of the following elements?

Mg with 14 neutrons

(3.11) Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region?

Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states.

(1.2) Which of the following elements has the mass spectrum represented above?

Mo

(1.1) A student obtains a sample of a pure solid compound. In addition to Avogadro's number, which of the following must the student know in order to determine how many molecules are in the sample?

Molar mass of the compound, mass of the sample

(6.1) Which of the following phase changes involves the transfer of heat from the surroundings to the system?

NH3(l) → NH3(g), because NH3 molecules in the liquid phase must absorb energy in order to overcome their intermolecular attractions and become free gas molecules.

(4.8) When 0.20 M NH4Cl(aq) and 0.20 M NaOH(aq) are mixed, the reaction represented by the equation above occurs and a strong smell of ammonia, NH3, is observed. Based on this information, which of the following statements is true?

NH4+(aq) is a stronger acid than H2O(l) is.

(3.12) The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10^−19 J. Using the wavelength information provided above, what is the color of the light?

Orange

(4.7) When C2H4(g) reacts with H2(g), the compound C2H6(g) is produced, as represented by the equation above. The reaction is correctly classified as which of the following types?

Oxidation-reduction, because H2(g) is oxidized.

(4.7) The compound C6H8O6 reacts with I2 according to the reaction represented by the equation above. The reaction is correctly classified as which of the following types?

Oxidation-reduction, because I2 is reduced.

(4.2) Equal volumes of 0.2M solutions of lead(II)nitrate and potassium bromide are combined to form lead(II)bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

Pb2+(aq) + 2Br−(aq) → PbBr2(s)

(4.2) The reaction between aqueous strontium chloride (SrCl2) and aqueous potassium sulfate (K2SO4) forms a precipitate of strontium sulfate (SrSO4). Which of the following represents the net ionic equation for the reaction?

Sr2+(aq) + SO42−(aq) → SrSO4(s)

(2.6) Which of the following statements, if true, would support the claim that the NO3− ion, represented above, has three resonance structures?

The NO3− ion is not a polar species.

(4.5) A 2mol sample of F2(g) reacts with excess NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq) but with 1 mol of F2(g), which of the following is correct?

The amount of OF2(g) produced is halved.

(3.5) A 1L sample of helium gas at 25°C and 1atm1atm is combined with a 1L sample of neon gas at 25°C and 1atm1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct?

The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

(2.1) Which of the following scientific claims about the bond in the molecular compound HF is most likely to be true?

The bond is highly polar.

(2.1) The elements C and Se have the same electronegativity value, 2.55. Which of the following claims about the compound that forms from C and Se is most likely to be true?

The carbon-to-selenium bond is nonpolar covalent.

(2.3) The energy required to dissociate an ionic solid into gaseous ions (lattice energy) for the compounds NaF and MgF2 is shown in the table above. On the basis of Coulomb's law, which of the following best helps to explain the large difference between the lattice energies of NaF and MgF2 ?

The charge of the Mg cation is larger than that of the Na cation.

(3.13) Using a spectrophotometer, a student measures the absorbance of four solutions of CuSO4 at a given wavelength. The collected data is given in the table above. Which of the following is the most likely explanation for the discrepant data in trial 4 ?

The concentration of the solution was actually lower than 0.150M.

(1.6) The photoelectron spectrum for the element nitrogen is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom?

The electrons in the 2p sublevel have the smallest binding energy.

(3.11) Infrared spectroscopy is a useful tool for scientists who want to investigate the structure of certain molecules. Which of the following best explains what can occur as the result of a molecule absorbing a photon of infrared radiation?

The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the types and strengths of different bonds in the molecules.

(6.5) A sample of CHCl3(s) was exposed to a constant source of heat for a period of time. The graph above shows the change in the temperature of the sample as heat is added. Which of the following best describes what occurs at the particle level that makes segment D longer than segment B?

The enthalpy of vaporization is greater than the enthalpy of fusion, because separating molecules completely from the liquid to form a gas requires more energy than separating molecules from their bound crystalline state to a liquid state.

(6.1) In the spring, blossoms on cherry trees can be damaged when temperatures fall below −2°C. When the forecast calls for air temperatures to be below −5°C for a few hours one night, a farmer sprays his blossoming cherry trees with water, claiming that the blossoms will be protected by the water as it freezes. Which of the following is a correct scientific justification for spraying water on the blossoms to protect them from temperatures below −2°C?

The freezing of water is an exothermic process; thus, water that freezes on the blossoms releases heat to keep the blossoms at or above −2°C.

(4.5) The reaction between C6H12O6 and O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2 was produced. Which of the following must be true?

The initial amount of C6H12O6 in the container must have been 0.10mol.

(1.4) A student is given two 10g samples, each a mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s) ?

The mass of Cl in each mixture

(1.4) A 5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl2 ?

The mass of Mg and the mass of Cl in the sample

(4.4) A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

(3.5) The graph above shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using information from the graph, and why?

The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass can be calculated using the equation KEavg=12mv2

(4.1) A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1MNaOH(aq) at 25°C was combined with 100.mL of 0.1MMgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur?

The resulting solution would contain a precipitate.

(3.1) Four different liquid compounds in flasks at 20°C are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?

The strength of the intermolecular forces between the particles in the liquids

(2.7) Lewis diagrams of molecules of three different hydrocarbons are shown above. Which of the following claims about the molecules is best supported by the diagrams?

The strongest carbon-to-carbon bond occurs in molecule 3.

(3.13) The diagrams above show the ultraviolet absorption spectra for two compounds. Diagram 1 is the absorption spectrum of pure acetone, a solvent used when preparing solutions for an experiment. Diagram 2 is the absorption spectrum of the solute for which the absorbance needs to be measured to determine its concentration. When the student reads the absorbance of the solution at 280nm, the result is too high. Which of the following is most likely responsible for the error in the measured absorbance?

The student forgot to calibrate the spectrophotometer first by using a cuvette containing only acetone.

(3.13) A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration.

The student made the standard curve above. Which of the following most likely caused the error in the point the student plotted at 0.050MCo2+(aq) ?

(4.1) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?

The temperature of the reaction mixture increases.

(3.11) Beta-carotene is an organic compound with an orange color. The diagram above shows the ultraviolet spectrum of beta-carotene. Which of the following statements is true about the absorption bands in the spectrum?

The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.

(1.8) All the chlorides of the alkaline earth metals have similar empirical formulas, as shown in the table above. Which of the following best helps to explain this observation?

The two valence electrons of alkaline earth metal atoms are relatively easy to remove.

(1.7) Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I?

There is a greater attraction between an added electron and the nucleus in Br than in I.

(4.5) A 100mL sample of 0.1MMgCl2(aq) and a 100mL100mL sample of 0.2MNaOH(aq) were combined, and Mg(OH)2(s) precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes in volume will double the amount of Mg(OH)2(s) produced?

Using twice the volume of MgCl2(aq) and twice the volume of NaOH(aq)

(1.3) Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions about the compounds is most likely to be answered by the results of the analysis?

What is the formula unit of each compound?

(1.7) Which of the following best helps explain why the electronegativity of Cl is less than that of F?

When Cl and F form bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the F bonding electrons are shielded from the positive F nucleus.

(1.3) A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment?

Which has the greater molar mass, X or Z?

(1.3) A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered?

Which sample has the higher purity?

(2.7) In the following diagrams, elements are represented by X and Z, which form molecular compounds with one another. Which diagram represents a molecule that has a bent molecular geometry?

Z=X=Z (X has two lone pairs)

(2.4) A particle-level diagram of a metallic element is shown above. Typically, metals are both malleable and ductile. The best explanation for these properties is that the electrons involved in bonding among metal atoms are

equally shared and form nondirectional bonds

(1.7) Which of the following represents an electron configuration that corresponds to the valence electrons of an element for which there is an especially large jump between the second and third ionization energies? (Note: n represents a principal quantum number equal to or greater than 2.)

ns2

(6.7) The oxidation of carbon monoxide can be represented by the chemical equation 2 CO(g)+O2(g)→2 CO2(g). The table above provides the average bond enthalpies for different bond types. Based on the information in the table, which of the following mathematical expressions is correct for the estimated enthalpy change for the reaction?

ΔHrxn=[2(1072kJmol)+(498kJmol)]−4(799kJmol)

(6.8) Based on the information in the table above, which of the following expressions gives the approximate ΔH° for the reaction represented by the following balanced chemical equation? Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)

ΔH°rxn=[2(0kJ/mol)+3(−394kJ/mol)]−[(−826kJ/mol)+3(−111kJ/mol)]

(6.8) The reaction between C(s) and H2O(g) is represented by the balanced chemical equation above. Based on the enthalpy change of the reaction (ΔH°) and the standard heats of formation (ΔH°f) given in the table below, what is the approximate ΔH°f for CO(g)?

−111kJ/mol

(6.7) Shown above are the equation representing the decomposition of H2O2(l) and a table of bond enthalpies. On the basis of the information, which of the following is the enthalpy of decomposition of 2 mol of H2O2(l) ?

−203kJ

(6.5) A 2.00mol sample of C2H5OH undergoes the phase transition illustrated in the diagram above. The molar enthalpy of vaporization, ΔHvap, of C2H5OH is +38.6kJ/mol. Which of the following best identifies the change in enthalpy in the phase transition shown in the diagram?

−77.2kJ

(6.8) The enthalpy change for the reaction 2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s) is −860kJ/mol. Based on the standard enthalpies of formation ΔH∘f provided in the table, what is the approximate ΔH∘f for Fe2O3(s)?

−820kJ/mol