A buffer is prepared by mixing 525 mL of 0.50 M formic acid, HCHO2, and 475 mL of 0.50 M sodium formate, NaCHO2. Calculate the pH. What would be the pH of 85 mL of the buffer to which 8.6 mL of 0.15...
Which of the following is the strongest base: NH3, C6H5NH2, or CH3NH2? See Table 16.2. TABLE 16.2 Base-lonization Constants at 25c Substance Formula Kp Aniline Dimethylamine Ethylamine Hydrazine...
A 50.0-mL sample of a 0.100 M solution of NaCN is titrated by 0.200 M HCl. Kb for CN is 2.0 10-5. Calculate the pH of the solution: a. Prior to the start of the titration; b. After the addition of...
Anhydrite is a calcium sulfate mineral deposited when seawater evaporates. What is the solubility of calcium sulfate, in grams per liter? Table 17.1 gives the solubility product constant for calcium...
Anhydrite is a mineral composed of CaSO4 (calcium sulfate). An inland lake has Ca2+ and SO42 concentrations of 0.0052 M and 0.0041 M, respectively. If these concentrations were doubled by...
A solution of 0.00016 M lead(II) nitrate, Pb(NO3)2, was poured into 456 mL of 0.00023 M sodium sulfate, Na2SO4. Would a precipitate of lead(II) sulfate, PbSO4, be expected to form if 255 mL of the...
A solution containing calcium ion and magnesium ion is buffered with ammonia-ammonium chloride. When carbonate ion is added to the solution, calcium carbonate precipitates but magnesium carbonate...
A solution contains 0.00750 M calcium ion. A concentrated sodium fluoride solution is added to precipitate calcium fluoride (assume no volume change). a. At what concentration of F does precipitate...
Although silver chloride is insoluble in water, it readily dissolves upon the addition of ammonia. a. What is the equilibrium constant for this dissolving process? AgCI(s) 2NH3(aq)Ag(N2 (aq) CI (aq)
A researcher found the solubility of lead(II) bromide in 0.100 M NaBr to be 1.31 g/L. What is the solubility product of lead(II) bromide?
An analytical chemist has a solution containing chloride ion, Cl-. She decides to determine the amount of chloride ion in the solution by titrating 50.0 mL of this solution by 0.100 MAgNO3. As a way...
A scientist was interested in how soluble rust is in acidic soils, so she set up an idealized problem to get an initial feel for the situation. A fairly acidic soil has a pH of 4.50. Also, rust is...
A solution is 1.5 10-4 M Zn2+ and 0.20 M HSO4. The solution also contains Na2SO4. What should be the minimum molarity of Na2SO4 to prevent the precipitation of zinc sulfide when the solution is...
A solution is 1.8 10-4 M Co2+ and 0.20 M HSO4. The solution also contains Na2SO4. What should be the minimum molarity of Na2SO4 to prevent the precipitation of cobalt(II) sulfide when the solution...
The solubility of silver bromate, AgBrO3, in water is 0.0072 g/L. Calculate Ksp.
A solution saturated in calcium hydroxide (limewater) has a pH of 12.35. What is Ksp for calcium hydroxide?
A student dissolved a compound in water and added hydrochloric acid. No precipitate formed. Next she bubbled H2S into this solution, but again no precipitate formed. However, when she made the...
A student was asked to identify a compound. In an effort to do so, he first dissolved the compound in water. He found that no precipitate formed when hydrochloric acid was added, but when H2S was...
A precipitate forms when a small amount of sodium hydroxide is added to a solution of aluminum sulfate. This precipitate dissolves when more sodium hydroxide is added. Explain what is happening.
Ammonia, NH3, is a base that ionizes to give NH4+ and OH (Kb = 1.8 10-5). You add magnesium sulfate to an ammonia solution. Calculate the concentration of Mg2+ ion when magnesium hydroxide, Mg(OH)2,...
A saturated solution of copper(II) iodate in pure water has a copper-ion concentration of 2.7 10-3 M. a. What is the molar solubility of copper iodate in a 0.35 M potassium iodate solution? b. What...
A saturated solution of lead iodate in pure water has an iodate-ion concentration of 8.0 10-5 M. a. What is the molar solubility of lead iodate in a 0.15 M lead nitrate solution at the same...
A solution contains 0.0150 M lead(II) ion. A concentrated sodium iodide solution is added to precipitate lead iodide (assume no volume change). a. At what concentration of I does precipitate start to...
Acetone, CH3COCH3, is a fragrant liquid that is used as a solvent for lacquers, paint removers, and nail polish remover. It burns in oxygen to give carbon dioxide and water: CH3COCH3(l) + 4O2(g)...
An ideal gas is cooled isothermally (at constant temperature). The internal energy of an ideal gas remains constant during an isothermal change. If q is 76 J, what are U and w?
Calculate So for the following reactions, using standard entropy values. a. 2Na(s) + Cl2(g) 2NaCl(s) b. Ag(s) + 1/2Cl2(g) AgCl(s) c. CS2(l) + 3O2(g) CO2(g) + 2SO2(g) d. 2CH3OH(l) + 3O2(g) 2CO2(g)...
Calculate the standard free energy of the following reactions at 25C, using standard free energies of formation. a. C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g) b. Na2CO3(s) + H + (aq) 2Na +(aq) + HCO3 (aq
Calculate the standard free-energy change and the equilibrium constant Kp for the following reaction at 25 C. See Table 18.2 for data. CO(g) 3H2(g) CH4(g) H20(g)
An experimenter placed 1.000 mol of H2 and 1.000 mol of I2 in a 1.000-L flask. The substances reacted to produce hydrogen iodide: When the contents of the flask came to equilibrium at 458oC, the...
Adenosine triphosphate, ATP, is used as a free-energy source by biological cells. (See the essay on page 750.) ATP hydrolyzes in the presence of enzymes to give ADP: ATP(aq) + H2O(l) ADP(aq) + H2PO4...
Write the expression for the thermodynamic equilibrium constant for each of the following reactions. a. b. c. CO(g) 2H2(g) CH,OHg) 2Ag (a CrO4 (aq)Ag CrO4(s) CaCO3(s) +2H (a)Ca2 (aH20CO2(8)
Compare the energies of the bonds broken and those formed (see Table 9.5) for the reaction HCN(g) + 2H2(g) CH3NH2(g) From this, conclude whether the reaction is exothermic or endothermic. What is...
Acetic acid, CH3COOH, freezes at 16.6oC. The heat of fusion, Hfus, is 69.0 J/g. What is the change of entropy, S, when 1 mol of liquid acetic acid freezes to the solid?
Acetone, CH3COCH3, boils at 56oC. The heat of vaporization of acetone at this temperature is 29.1kJ/mol. What is the entropy change when 1 mol of liquid acetone vaporizes at 56oC?
Acetic acid in vinegar results from the bacterial oxidation of ethanol. C2H5OH(l) + O2(g) CH3COOH(l) + H2O(l) What is So for this reaction? Use standard entropy values. (See Appendix C for data.)
The reaction N2(g) + 3H2(g) 2NH3(g) is spontaneous at room temperature but becomes nonspontaneous at a much higher temperature. From this fact alone, obtain the signs of Ho, and So, assuming that Ho...
a. Why are some reactions exothermic and others endothermic? b. Discuss the driving force in a spontaneous reaction that is highly exothermic and in one that is endothermic.
A nuclear power plant emits into the atmosphere a very small amount of krypton-85, a radioactive isotope with a half-life of 10.76 y. What fraction of this krypton-85 remains after 25.0 y?
a. Write the abbreviated notation for the reaction b. Write the nuclear equation for the bombardment reaction 13
A sample of sodium phosphate, Na3PO4, weighing 54.5 mg contains radioactive phosphorus-32 (with mass 32.0 amu). If 15.6% of the phosphorus atoms in the compound is phosphorus-32 (the remainder is...
A sample of sodium thiosulfate, Na2S2O3, weighing 38.1 mg contains radioactive sulfur-35 (with mass 35.0 amu). If 22.3% of the sulfur atoms in the compound is sulfur-35 (the remainder is naturally...
A radioactive sample with a half-life of 10 minutes is placed in a container. a. Complete the pictures below depicting the amount of this sample at the beginning of the experiment (t = 0 min) and 30...
What are the six common types of radioactive decay? What condition usually leads to each type of decay?
Actinium was discovered in uranium ore residues by Andr-Louis Debierne. Actinium-227 decays by emitting a single alpha particle. Write the nuclear equation for this decay.
A proton is accelerated to 12.6 MeV per particle. What is this energy in kJ/mol?
An alpha particle is accelerated to 23.1 MeV per particle. What is this energy in kJ/mol?
Gold-198 has a half-life of 2.69 d. What is the activity (in curies) of a 0.86-mg sample?
A sample of a phosphorus compound contains phosphorus-32. This sample of radioactive isotope is decaying at the rate of 6.0 1012 disintegrations per second. How many grams of 32P are in the sample?...
A sample of sodium thiosulfate, Na2S2O3, contains sulfur-35. Determine the mass of 35S in the sample from the decay rate, which was determined to be 7.7 1011 disintegrations per second. The...
A sample of sodium-24 was administered to a patient to test for faulty blood circulation by comparing the radioactivity reaching various parts of the body. What fraction of the sodium 24 nuclei would...
A solution of sodium iodide containing iodine-131 was given to a patient to test for malfunctioning of the thyroid gland. What fraction of the iodine-131 nuclei would remain undecayed after 7.0 d? If...
A sample of iron-59 initially registers 125 counts per second on a radiation counter. After 10.0 d, the sample registers 107 counts per second. What is the half-life (in days) of iron-59?
A sample of copper-64 gives a reading of 88 counts per second on a radiation counter. After 9.5 h, the sample gives a reading of 53 counts per second. What is the half-life (in hours) of copper-64?
Carbon from a cypress beam obtained from the tomb of Sneferu, a king of ancient Egypt, gave 8.1 disintegrations of 14C per minute per gram of carbon. How old is the cypress beam? Carbon from living...
Carbon from the Dead Sea Scrolls, very old manuscripts found in Israel, gave 12.1 disintegrations of 14C per minute per gram of carbon. How old are the manuscripts? Carbon from living material gives...
Aluminum-27 is the only stable isotope of aluminum. Predict how aluminum-24 will decay and how aluminum-30 will decay.
When technetium-99m decays to technetium-99, a gamma photon corresponding to an energy of 0.143 MeV is emitted. What is the wavelength of this gamma emission? What is the difference in mass between...
Complete and balance the following equations. a. KOH(aq) + MgCl2(aq) b. Mg(s) + CuSO4(aq) c. Sr(s) + H2O(l) d. SrCO3(s) + HCl(aq) e. Ba(OH)2(aq) + CO2(g)
Ammonia reacts with oxygen in the presence of a platinum catalyst to give nitric oxide, NO. How many grams of oxygen are required in this reaction to give 3.00 g NO?
Although phosphorus pentabromide exists in the vapor phase as PBr5 molecules, in the solid phase the substance is ionic and has the structure [PBr4+]Br. What is the expected geometry of PBr4+?...
Although phosphorus pentachloride exists in the vapor phase as PCl5 molecules, in the solid phase the substance is ionic and has the structure [PCl4+][PCl6]. What is the expected geometry of PCl6?...
(a) Write electrode half-reactions for the electrolysis of fused sodium chloride. (b) Do the same for fused sodium hydroxide. The hydroxide ion is oxidized to oxygen and water.
A sample of zinc ore contains 87.0% sphalerite, ZnS. How many metric tons of Zn can be obtained from 1.00 metric ton of the zinc ore?
A sample of lead ore contains 78.0% galena, PbS. How many metric tons of Pb can be obtained from 1.00 metric ton of the lead ore?
An antacid tablet consists of calcium carbonate with other ingredients. The calcium carbonate in a 0.9863-g sample of the antacid was dissolved in 50.00 mL of 0.5068 M HCl, then titrated with 41.23...
A sample of limestone was dissolved in hydrochloric acid, and the carbon dioxide gas that evolved was collected. If a 0.1662-g sample of limestone gave 34.56 mL of dry carbon dioxide gas at 745 mmHg...
A sample of rock containing magnesite, MgCO3, was dissolved in hydrochloric acid, and the carbon dioxide gas that evolved was collected. If a 0.1504-g sample of the rock gave 37.71 mL of dry carbon...
Ascorbic acid, C6H8O6 (vitamin C), is a reducing agent. The amount of this acid in solution can be determined quantitatively by a titration procedure involving iodine, I2, in which ascorbic acid is...
(a) Nitrogen dioxide can be prepared by heating lead nitrate to about 400oC. The products, in addition to nitrogen dioxide, are lead (II) oxide and oxygen. Write the equation for this decomposition....
A sample of a metal sulfide weighing 6.125 g was roasted in air to obtain 5.714 g of the oxide. The oxide was then dissolved in dilute sulfuric acid, which yielded a white precipitate. The mass of...
A mixture contained aluminum sulfate and sodium sulfate. A sample of the mixture weighing 3.458 g was dissolved in water and treated with sodium hydroxide solution to yield a precipitate. The...
A quantity of white phosphorus was burned in an excess of oxygen. The product of this combustion was dissolved in water to give 1.258 L of solution. This solution was found to have a pH of 2.091. (a)...
A white crystalline material contained sodium acetate and sodium chloride. To determine the composition of this mixture, a researcher dissolved 0.613 g of this mixture in water to give 25.0 mL of...
Aluminum hydroxide is an amphoteric substance. What does this mean? Write equations to illustrate.
(a) Use crystal field theory to describe a high-spin octahedral complex of Fe2+. (b) Do the same for a low-spin complex.
Write the balanced equation for the reaction of iron(II) ion with nitrate ion in acidic solution. Nitrate ion is reduced to NO.
Determine whether there are optical isomers of any of the following. If so, sketch the isomers. a. cis-[Co(NH3)2(en)2]3+ b. trans-[IrCl2(C2O4)2]3
According to IUPAC rules, what is the name of each of the following compounds? a. CH3COCH2CH3 b. CH3CH2CH2CHO c. d. CH3 H-CCH2CH2CCH: CH3
An addition polymer is prepared from vinylidene chloride, CH2=CCl2. Write the structure of the addition polymer.
Alanine has the structure Draw the zwitterion that would exist at neutral pH. CH3-C-COOH NH
Aspartame, a low-calorie sweetener, is the methyl esterof a dipeptide. Its structure is a. Suppose aspartame is hydrolyzed (reacted with water). Give the names of the amino acids obtained from this...
Consider the zwitterion of the amino acid alanine, which is the predominant form of the acid at neutral pH. Draw its structural formula. Imagine that the pH of a solution of alanine is gradually...
A polymer is hydrolyzed to give an acidic substance and a compound that was found to have properties of an alcohol. When this compound was oxidized, it produced an acid whose molecular mass was found...
(a) When a 0.235-g sample of benzoic acid is combusted in a bomb calorimeter (Figure 5.19), the temperature rises 1.642 C. When a 0.265-g sample of caffeine, C8H10O2N4, is burned, the temperature...
The hydrocarbons acetylene (C2H2) and benzene (C6H6) have the same empirical formula. Benzene is an "aromatic" hydrocarbon, one that is unusually stable because of its structure. (a) By using the...
It is estimated that the net amount of carbon dioxide fixed by photosynthesis on the landmass of Earth is 5.5 1016 g/yr of CO2. Assume that all this carbon is converted into glucose. (a) Calculate...
Consider the following unbalanced oxidation-reduction reactions in aqueous solution: (a) Balance each of the reactions. (b) By using data in Appendix C, calculate H for each of the reactions. (c)...
A sample of a hydrocarbon is combusted completely in O2(g) to produce 21.83 g CO2(g), 4.47 g H2O(g), and 311 kJ of heat. (a) What is the mass of the hydrocarbon sample that was combusted? (b) What is...
A watt is a measure of power (the rate of energy change) equal to 1 J/s. (a) Calculate the number of joules in a kilowatt-hour. (b) An adult person radiates heat to the surroundings at about the same...
(a) What is meant by the term system in thermodynamics? (b) What is a closed system? (c) What do we call the part of the universe that is not part of the system?
(a) What is work? (b) How do we determine the amount of work done, given the force associated with the work?
(a) What is heat? (b) Under what conditions is heat transferred from one object to another?
(a) State the first law of thermodynamics. (b) What is meant by the internal energy of a system? (c) By what means can the internal energy of a closed system increase?
(a) Write an equation that expresses the first law of thermodynamics in terms of heat and work. (b) Under what conditions will the quantities q and w be negative numbers?
The precipitation reaction between AgNO3(aq) and NaCl(aq) proceeds as follows: (a) By using Appendix C, calculate ÎH° for the net ionic equation of this reaction. (b) What would you expect...
The methane molecule, CH4, has the geometry shown in Figure 2.19. Imagine a hypothetical process in which the methane molecule is "expanded," by simultaneously extending all four C-H bonds to...
(a) What is meant by the term state function? (b) Give an example of a quantity that is a state function and one that is not. (c) Is the volume of the system a state function? Why or why not?
(a) Why is the change in enthalpy usually easier to measure than the change in internal energy? (b) H is a state function, but q is not a state function. Explain. (c) For a given process at constant...
(a) Under what condition will the enthalpy change of a process equal the amount of heat transferred into or out of the system? (b) During a constant-pressure process, the system releases heat to the...
(a) What are the units of molar heat capacity? (b) What are the units of specific heat? (c) If you know the specific heat of copper, what additional information do you need to calculate the heat...