Draw each amino acid in its dipolar ion form.a. Valb.

Classify each saccharide as an aldose or a ketose. Also classify each as a triose, tetrose, pentose, etc.

How many chiral carbon atoms are in each of the structures in Problem 39?

How many chiral carbon atoms are in each of the structures in Problem 40?

Problem 43E Draw structures for the straight-chain and ring forms of glucose.

Problem 44E Draw structures for the straight-chain and ring forms of fructose.

Draw the products that result from the hydrolysis of the carbohydrate.

Draw the products that result from the hydrolysis of the carbohydrate.

Problem 47E Draw the structure of sucrose. Label the glucose and fructose rings in this disaccharide.

Problem 48E Lactose is a disaccharide of glucose and galactose. Draw the structure of lactose.

Problem 49E Draw each amino acid in its dipolar ion form. a. Thr b. Ala c. Leu d. Lys

Problem 50E Draw each amino acid in its dipolar ion form. a. Val b. Phe c. Tyr d. Cys

Problem 51E Draw the structures of the two enantiomers of alanine.

Problem 52E Draw the structures of the two enantiomers of cysteine.

Problem 53E How many different tripeptides can form from serine, glycine, and cysteine? List the arnino acid sequence of each one.

Problem 54E How many dipeptides can form from leucine and serine? List the arnino acid sequence for each one.

Problem 55E Draw the reaction by which serine and tyrosine form a peptide bond.

Problem 56E Draw the reaction by which valine and asparagine form a peptide bond.

Problem 57E Draw a structure for each tripeptide. a. Gln-Met-Cys b. Ser-Leu-Cys c. Cys-Leu-Ser

Problem 58E Draw a structure for each tetrapeptide. a. Ser-Ala-Leu-Cys b. Gln-Met-Cys-Gly c. Gly-Cys-Met-GIn

Problem 59E A phenylalanine amino acid on a protein strand undergoes hydrophobic interactions with another phenylalanine amino acid that is 26 amino acid units away. The resulting fold in the protein is an example of which kind of structure? (primary, secondary, tertiary, or quaternary)

Problem 60E A phenylalanine amino acid on a protein strand undergoes hydrophobic interactions with another phenylalanine amino acid that is 26 amino acid units away. The resulting fold in the protein is an example of which kind of structure? (primary, secondary, tertiary, or quaternary)

Problem 66E Draw the structures of the three pyrimidine bases in nucleic acids.

Problem 65E Draw the structures of the two purine bases in nucleic acids.

Determine whether or not each structure is a nucleotide. For each nucleotide, identify the base as A, T, C, or G.

Problem 62E A dimeric protein is composed of two individual chains of amino acids. The way these two chains fit together is an example of which kind of structure? (primary, secondary, tertiary, or quaternary)

The amino acid sequence in one section of a protein is shown here. It represents which kind of structure? (primary, secondary, tertiary, or quaternary)

Determine whether or not each structure is a nucleotide. For each nucleotide, identify the base as A, T, C, or G.

Describe the main steps used to purify metals.

Describe the extraction of iron in a blast furnace.

Briefly discuss the steelmaking process.

In the Mond process for the purification of nickel, CO is passed over metallic nickel to give Ni(CO)4: Ni(s) 1 4CO(g) Ni(CO)4(g) Given that the standard free energies of formation of CO(g) and Ni(CO)4(g) are 2137.3 kJ/mol and 2587.4 kJ/mol, respectively, calculate the equilibrium constant of the reaction at 80C. (Assume DGf to be independent of temperature.)

Copper is purified by electrolysis (see Figure 21.6). A 5.00-kg anode is used in a cell where the current is 37.8 A. How long (in hours) must the current run to dis solve this anode and electroplate it onto the cathode?

Consider the electrolytic procedure for purifying copper described in Figure 21.6. Suppose that a sample of copper contains the following impurities: Fe, Ag, Zn, Au, Co, Pt, and Pb. Which of the metals will be oxidized and dissolved in solution and which will be unaffected and simply form the sludge that accumulates at the bottom of the cell?

How would you obtain zinc from sphalerite (ZnS)?

Starting with rutile (TiO2), explain how you would obtain pure titanium metal. (Hint: First convert TiO2 to TiCl4. Next, reduce TiCl4 with Mg. Look up physical properties of TiCl4, Mg, and MgCl2 in a chemistry handbook.)

A certain mine produces 2.0 3 108 kg of copper from chalcopyrite (CuFeS2) each year. The ore contains only 0.80 percent Cu by mass. (a) If the density of the ore is 2.8 g/cm3 , calculate the volume (in cm3 ) of ore removed each year. (b) Calculate the mass (in kg) of SO2 produced by roasting (assume chalcopyrite to be the only source of sulfur).

Which of the following compounds would require electrolysis to yield the free metals? Ag2S, CaCl2, NaCl, Fe2O3, Al2O3, TiCl4.

Although iron is only about two-thirds as abundant as aluminum in Earths crust, mass for mass it costs only about one-quarter as much to produce. Why?

Define the following terms: conductor, insulator, semiconducting elements, donor impurities, acceptor impurities, n-type semiconductors, p-type semiconductors.

Briefly discuss the nature of bonding in metals, insulators, and semiconducting elements.

Describe the general characteristics of n-type and p-type semiconductors.

State whether silicon would form n-type or p-type semiconductors with the following elements: Ga, Sb, Al, As.

How is sodium prepared commercially?

Why is potassium usually not prepared electrolytically from one of its salts?

Describe the uses of the following compounds: NaCl, Na2CO3, NaOH, KOH, KO2.

Under what conditions do sodium and potassium form Na2 and K2 ions?

Complete and balance the following equations: (a) K(s) 1 H2O(l) (b) NaH(s) 1 H2O(l) (c) Na(s) 1 O2(g) (d) K(s) 1 O2(g)

Write a balanced equation for each of the following reactions: (a) sodium reacts with water; (b) an aqueous solution of NaOH reacts with CO2; (c) solid Na2CO3 reacts with a HCl solution; (d) solid NaHCO3 reacts with a HCl solution; (e) solid NaHCO3 is heated; (f ) solid Na2CO3 is heated.

Sodium hydride (NaH) can be used as a drying agent for many organic solvents. Explain how it works.

Calculate the volume of CO2 at 10.0C and 746 mmHg pressure obtained by treating 25.0 g of Na2CO3 with an excess of hydrochloric acid.

List the common ores of magnesium and calcium.

How are the metals magnesium and calcium obtained commercially?

From the thermodynamic data in Appendix 3, calculate the DH values for the following decompositions: (a) MgCO3(s) MgO(s) 1 CO2(g) (b) CaCO3(s) CaO(s) 1 CO2(g) Which of the two compounds is more easily decomposed by heat?

Starting with magnesium and concentrated nitric acid, describe how you would prepare magnesium oxide. [Hint: First convert Mg to Mg(NO3)2. Next, MgO can be obtained by heating Mg(NO3)2.]

Describe two ways of preparing magnesium chloride.

The second ionization energy of magnesium is only about twice as great as the first, but the third ionization energy is 10 times as great. Why does it take so much more energy to remove the third electron?

List the sulfates of the Group 2A metals in order of increasing solubility in water. Explain the trend. (Hint: You need to consult a chemistry handbook.)

Helium contains the same number of electrons in its outer shell as do the alkaline earth metals. Explain why helium is inert whereas the Group 2A metals are not.

When exposed to air, calcium first forms calcium oxide, which is then converted to calcium hydroxide, and finally to calcium carbonate. Write a balanced equation for each step.

Write chemical formulas for (a) quicklime, (b) slaked lime, (c) limewater.

Describe the Hall process for preparing aluminum.

What action renders aluminum inert?

Before Hall invented his electrolytic process, aluminum was produced by the reduction of its chloride with an active metal. Which metals would you use for the production of aluminum in that way?

With the Hall process, how many hours will it take to deposit 664 g of Al at a current of 32.6 A?

Aluminum forms the complex ions AlCl4 2 and AlF6 32. Describe the shapes of these ions. AlCl6 32 does not form. Why? (Hint: Consider the relative sizes of Al31, F2, and Cl2 ions.)

The overall reaction for the electrolytic production of aluminum by means of the Hall process may be represented as Al2O3 (s) 1 3C(s) 2Al(l) 1 3CO(g) At 1000C, the standard free-energy change for this process is 594 kJ/mol. (a) Calculate the minimum voltage required to produce 1 mole of aluminum at this temperature. (b) If the actual voltage applied is exactly three times the ideal value, calculate the energy required to produce 1.00 kg of the metal.

In basic solution, aluminum metal is a strong reducing agent and is oxidized to AlO2 2. Give balanced equations for the reaction of Al in basic solution with the following: (a) NaNO3, to give ammonia; (b) water, to give hydrogen; (c) Na2SnO3, to give metallic tin.

Write a balanced equation for the thermal decomposition of aluminum nitrate to form aluminum oxide, nitrogen dioxide, and oxygen gas

Describe some of the properties of aluminum that make it one of the most versatile metals known.

The pressure of gaseous Al2Cl6 increases more rapidly with temperature than predicted by the ideal gas equation even though Al2Cl6 behaves like an ideal gas. Explain.

Starting with aluminum, describe with balanced equations how you would prepare (a) Al2Cl6, (b) Al2O3, (c) Al2(SO4)3, (d) NH4Al(SO4)2 ? 12H2O

Explain the change in bonding when Al2Cl6 dissociates to form AlCl3 in the gas phase.

In steelmaking, nonmetallic impurities such as P, S, and Si are removed as the corresponding oxides. The inside of the furnace is usually lined with CaCO3 and MgCO3, which decompose at high temperatures to yield CaO and MgO. How do CaO and MgO help in the removal of the nonmetallic oxides?

When 1.164 g of a certain metal sulfide was roasted in air, 0.972 g of the metal oxide was formed. If the oxidation number of the metal is 12, calculate the molar mass of the metal.

An early view of metallic bonding assumed that bonding in metals consisted of localized, shared electron-pair bonds between metal atoms. What evidence would help you to argue against this viewpoint?

Referring to Figure 21.6, would you expect H2O and H1 to be reduced at the cathode and H2O oxidized at the anode?

A 0.450-g sample of steel contains manganese as an impurity. The sample is dissolved in acidic solution and the manganese is oxidized to the permanganate ion MnO4 2. The MnO4 2 ion is reduced to Mn21 by reacting with 50.0 mL of 0.0800 M FeSO4 solution. The excess Fe21 ions are then oxidized to Fe31 by 22.4 mL of 0.0100 M K2Cr2O7. Calculate the percent by mass of manganese in the sample

Given that DGf(Fe2O3) 5 2741.0 kJ/mol and that DGf(Al2O3) 5 21576.4 kJ/mol, calculate DG for the following reactions at 25C: (a) 2Fe2O3(s) 4Fe(s) 1 3O2(g) (b) 2Al2O3(s) 4Al(s) 1 3O2(g)

Use compounds of aluminum as an example to explain what is meant by amphoterism.

When an inert atmosphere is needed for a metallurgical process, nitrogen is frequently used. However, in the reduction of TiCl4 by magnesium, helium is used. Explain why nitrogen is not suitable for this process.

It has been shown that Na2 species form in the vapor phase. Describe the formation of the disodium mole cule in terms of a molecular orbital energylevel diagram. Would you expect the alkaline earth metals to exhibit a similar property?

Explain each of the following statements: (a) An aqueous solution of AlCl3 is acidic. (b) Al(OH)3 is soluble in NaOH solutions but not in NH3 solution.

Write balanced equations for the following reactions: (a) the heating of aluminum carbonate; (b) the reaction between AlCl3 and K; (c) the reaction between solutions of Na2CO3 and Ca(OH)2.

Write a balanced equation for the reaction between calcium oxide and dilute HCl solution.

What is wrong with the following procedure for obtaining magnesium? MgCO3 MgO(s) 1 CO2(g) MgO(s) 1 CO(g) Mg(s) 1 CO2(g)

Explain why most metals have a flickering appearance

Predict the chemical properties of francium, the last member of Group 1A.

Describe a medicinal or health-related application for each of the following compounds: NaF, Li2CO3, Mg(OH)2, CaCO3, BaSO4, Al(OH)2NaCO3. (You would need to do a Web search for some of these compounds.)

The following are two reaction schemes involving magnesium. Scheme I: When magnesium burns in oxygen, a white solid (A) is formed. A dissolves in 1 M HCl to give a colorless solution (B). Upon addition of Na2CO3 to B, a white precipitate is formed (C). On heating, C decomposes to D and a colorless gas is generated (E). When E is passed through limewater [an aqueous suspension of Ca(OH)2], a white precipitate appears (F). Scheme II: Magnesium reacts with 1 M H2SO4 to produce a colorless solution (G). Treating G with an excess of NaOH produces a white precipitate (H). H dissolves in 1 M HNO3 to form a colorless solution. When the solution is slowly evaporated, a white solid (I) appears. On heating I, a brown gas is given off. Identify AI and write equations representing the reactions involved.

Lithium and magnesium exhibit a diagonal relationship in some chemical properties. How does lithium resemble magnesium in its reaction with oxygen and nitrogen? Consult a handbook of chemistry and compare the solubilities of carbonates, fluorides, and phosphates of these metals.

To prevent the formation of oxides, peroxides, and superoxides, alkali metals are sometimes stored in an inert atmosphere. Which of the following gases should not be used for lithium? Why? Ne, Ar, N2, Kr.

Which of the following metals is not found in the free state in nature: Ag, Cu, Zn, Au, Pt?

After heating, a metal surface (such as that of a cooking pan or skillet) develops a color pattern like an oil slick on water. Explain.

Chemical tests of four metals A, B, C, and D show the following results. (a) Only B and C react with 0.5 M HCl to give H2 gas. (b) When B is added to a solution containing the ions of the other metals, metallic A, C, and D are formed. (c) A reacts with 6 M HNO3 but D does not. Arrange the metals in the increasing order as reducing agents. Suggest four metals that fit these descriptions.

The electrical conductance of copper metal decreases with temperature, but that of a CuSO4 solution increases with temperature. Explain.

As stated in the chapter, potassium superoxide (KO2) is a useful source of oxygen employed in breathing equipment. Calculate the pressure at which oxygen gas stored at 20C would have the same density as the oxygen gas provided by KO2. The density of KO2 at 20C is 2.15 g/cm3 .

A sample of 10.00 g of sodium reacts with oxygen to form 13.83 g of sodium oxide (Na2O) and sodium peroxide (Na2O2). Calculate the percent composition of the mixture.

Problem 1E What is biochemistry? What significant advances in biochemistry have helped diabetics?

Which compound is a lipid?

Problem 2E What is a lipid? What roles do lipids play in living organisms?

Which compound is a carbohydrate?

Problem 3E What is a fatty acid? Draw the general structure of a fatty acid.

Which compound is an amino acid?

Problem 4E What effect do double bonds have within the hydrocarbon chain of a fatty acid?

Problem 4SAQ The sequence of amino acids in a protein chain is an example of which kind of protein structure? a) primary b) secondary c) tertiary d) quaternary

Problem 5E What are triglycerides? Draw a general structure of a triglyceride.

Problem 5SAQ A section of DNA contains the bases ATTCGGAA. What is the correct sequence of bases in the complementary strand? a) CGGATTCC b) ATTCGGAA c) AAGGCTTA d) TAAGCCTT

Explain the difference, both in terms of structure and in terms of properties, between a saturated fat and an unsaturated fat.

Problem 6SAQ A codon is a sequence within DNA that codes for what? a) an amino acid b) a protein c) a carbohydrate d) a fat

Problem 7E Describe the basic structure of phospholipids and glycolipids. What functions do these lipids have in living organisms?

Problem 7SAQ Which of the functions listed is not attributed to proteins? a) catalyze biochemical reactions b) transport substances from one place to another c) mediate muscle contraction d) none of the above (all of these functions are attributed to proteins)

Problem 8E What is a steroid? List some functions of steroids.

Problem 8SAQ Which is a primary function of nucleic acids? a) energy storage b) coding the amino acid sequence for proteins c) oxygen transport d) regulation of metabolic processes

Problem 9E What are carbohydrates? What role do they play in living organisms?

Problem 9SAQ Peptide bonds occur in which type of biochemical compounds? a) lipids b) carbohydrates c) proteins d) nucleic acids

Problem 10E How do monosaccharides and disaccharides differ? Aldoses and ketoses?

Problem 10SAQ How many nucleotides are required to code for all of the amino acids in a protein that contains 186 amino acids? a) 186 b) 372 c) 553 d) 1

Problem 11E How do simple and complex carbohydrates differ?

Problem 12E How do cellulose, starch, and glycogen differ? Describe the function of each.

Problem 13E What roles do proteins play in living organisms? List specific examples.

How do the properties of the R groups in amino acids relate to the properties of proteins?

Problem 14E Describe the basic structure of an arnino acid. How are arnino acids linked together to form proteins?

Problem 16E Why are amino acids chiral?

Problem 17E Draw the structure of a neutral arnino acid and its dipolar ion.

Problem 18E Draw the structure of any two arnino acids, showing how they link together to form a dipeptide.

Problem 19E Why is protein structure important?

Problem 20E How do fibrous proteins and globular proteins differ?

Problem 21E Describe the various levels of protein structure (primary, secondary, tertiary, and quaternary).

Problem 22E What types of interactions or bonds maintain each of the structures listed in the previous problem?

Describe the secondary structures known as \(\alpha\) -helix and \(\beta\) -pleated sheet.

Problem 24E What is the function of nucleic acids in living organisms?

Problem 25E What is the general structure of a nucleic acid?

Problem 26E The bases in nucleic acids are complementary. What does this mean?

Problem 27E What is a codon? A gene? A chromosome?

Problem 28E Do most cells contain complete copies of an organism's DNA? Do most cells express all of the genes contained in their DNA?

Explain the mechanism by which DNA is replicated.

Explain the mechanism by which proteins are synthesized from the information contained within DNA.

Determine whether or not each molecule is a lipid. If the molecule is a lipid, indicate the kind of lipid. If it is a fatty acid or a triglyceride, classify it as saturated or unsaturated.

Determine whether or not each molecule is a lipid. If the molecule is a lipid, state the kind of lipid. If it is a fatty acid or a triglyceride, classify it as saturated or unsaturated.

Determine whether or not each molecule is a fatty acid. If it is a fatty acid, classify it as saturated, monounsaturated, or polyunsaturated.

Which fatty acid is most likely to be a solid at room temperature?

Draw structures showing the reaction of glycerol with linoleic acid to form the triglyceride trilinolean. Would you expect this triglyceride to be a fat or an oil?

Problem 36E Draw structures showing the reaction of glycerol with rnvristic acid to form the triglyceride trimyristin. Would you expect this triglyceride to be a fat or an oil?

Determine whether or not each structure is a carbohydrate. If the molecule is a carbohydrate, classify it as a monosaccharide, disaccharide, or trisaccharide.

Determine whether or not each structure is a carbohydrate. If the molecule is a carbohydrate, classify it as a monosaccharide, disaccharide, or trisaccharide.

Classify each saccharide as an aldose or a ketose. Also classify each as a triose, tetrose, pentose, etc.

Draw the DNA strand that is complementary to the DNA strand shown here.

Draw the DNA strand that is complementary to the DNA strand shown here.

Problem 69E A monomeric protein contains 154 amino acids. How many codons code for these arnino acids? How many nucleotides?

Problem 70E A dimeric protein contains 142 arnino acids in one strand and 148 in the other. How many codons code for these arnino acids? How many nucleotides?

Problem 71E Determine the class of biochemical compound that contains each type of linkage. a. peptide bonds b. glycosidic linkage c. ester linkage

Problem 72E Name the type of polymer associated with each monomer. a. nucleotide b. arnino acid c. saccharide

Problem 73E What is the difference between a codon and a nucleotide? A codon and a gene?

Problem 74E What is the difference between a fatty acid and a triglyceride? A triglyceride and a phospholipid?

The amino acid alanine has the condensed structural formula shown here: Determine the VSEPR geometry about each internal atom and make a three-dimensional sketch of the molecule.

The amino acid serine has the condensed structural formula shown here: Determine the VSEPR geometry about each internal atom and make a three-dimensional sketch of the molecule.

Which amino acids in Table 21.3 are most likely to be involved in hydrophobic interactions?

Problem 78E Sickle-cell anemia is caused by a genetic defect that substitutes valine for glutamic acid at one position in two of the four chains of the hemoglobin protein. The result is a decrease in the water solubility of hemoglobin. Examine the structures of valine and glutamic acid and explain why this occurs.

Determining the amino acid sequence in a protein usually involves treating the protein with various reagents that break up the protein into smaller fragments that can be individually sequenced. Treating a particular 11-amino acid polypeptide with 1 reagent produced the fragments: Treating the same polypeptide with a different reagent produced the fragments: What is the amino acid sequence of the polypeptide?

Treating a particular polypeptide with one reagent (as described in the previous problem) produced the fragments: Treating the same polypeptide with a different reagent produced the fragments: What is the amino acid sequence of the polypeptide?

Naturally occurring d-glucose is one of a pair of enantiomers. Its mirror image is l-glucose. Draw the two cyclic six-membered isomers of l-glucose that differ in the configuration around C1 and indicate which is and which is .

Problem 82E Calculate the mass percent of phosphorus in a strand of DNA that consists of equal amounts of each of the four N-bases.

Problem 83E The double helical structure of DMA disrupts on heating but reforms on cooling. Use thermodynamic reasoning to account for these observations.

Problem 84E From the structural formula of cholesterol shown on page 1006 , determine (a) the composition, and (b) the number of chiral centers.

One way to fight viral infections is to prevent a virus from replicating its DNA. Without DNA replication, the virus cannot multiply. Some viral drug therapies cause the introduction of fake nucleotides into cells. When the virus uses one of these fake nucleotides in an attempt to replicate its DNA, the fake nucleotide doesn’t work and viral DNA replication is halted. For example, azidothymidine (AZT), a drug used to fight the human immunodeficiency virus (HIV) that causes AIDS, results in the introduction of the following fake thymine-containing nucleotide into cells. Examine the structures of the real nucleotide and the AZT fake nucleotide. Propose a mechanism for how this fake nucleotide might halt DNA replication.

Draw each molecule and identify the chiral centers within them. a. ribose b. galactose c. 5-deoxyribose ( Hint: The 5 indicates that the oxygen is removed from the 5th carbon.)

Glucose transport across the red blood cell membranes (erythrocyte membrane) is a well-studied system. One laboratory project obtained the data shown here for glucose transport. The kinetics of glucose transport through the membrane follows the Michaelis–Menten equation: The Michaelis–Menten equation can be rearranged so that a plot 1/V0 versus 1/[glucose] produces a straight line. Rearrange the equation and plot the data in order to determine Kt and Vmax for glucose transport across the erythrocyte membrane.

Problem 88E Eukaryotic DNA is equipped with special ends called telomers. Telomers are made up of hexanucleotide sequences that repeat at the ends of the DNA. For example, human DNA features repeating AGGGTT sequences. Functionally, telomers protect the ends of chromosomes from being treated as a broken piece of DNA in need of repair. Interestingly, telomers are cut off each time the DNA is replicated, indicating a possible cellular clock that allows only a certain number of cellular replications. Telomerase is the enzyme that catalyzes the synthesis of telomers. Telomerase is present in limited quantities within certain cells such as fetal tissue, adult male germ cells, and stern cells. It is also found in over 35% of tumor cells. Researchers speculate that the telomerase activity may be linked to cancer. Propose an explanation for why telomerase activity could be associated with cancer and speculate on ways in which cancer treatments in the future may capitalize on research on this enzyme.

Problem 90E How many different tetrapeptides can form from four different arnino acids?

Write the major equilibrium that is established in a solution of glycine at pH = 2 and at pH = 10. The \(\mathrm{p} K_{\mathrm{a}}\) of the COOH group is 2.3 and the \(\mathrm{p} K_{\mathrm{a}}\) of the \(\mathrm{NH}_3^{\ +}\) group is 9.6. Determine the relative concentrations of each member of the relevant conjugate acid–base pair at pH = 2 and pH = 10. Calculate the pH at which glycine is neutral.

Problem 91E Could the genetic code have been based on just three bases and three-base codons? Explain why or why not. (Assume that the code must accommodate 20 different amino acids.)

Problem 92E The genetic code is random, which means that a particular codon could have coded for a different arnino acid. The genetic code is also nearly universal, meaning that it is the same code in nearly all organisms (and in the few where it differs, it does so only slightly). If scientists ever find life on another planet, they will be curious to know its genetic code. What would a completely different genetic code indicate about the origin of the life-form? What would a genetic code identical to terrestrial life indicate?