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chemistry and chemical reactivity
Questions and Answers of
Chemistry And Chemical Reactivity
A reaction important in smog formation is(a) If the initial concentrations are [O3] = 1.0 ×10−6 M, [NO] = 1.0 × 10−5 M, [NO2] = 2.5 ×10−4 M, and [O2] = 8.2 × 10−3 M, is the M system at
Sodium cyanide is the salt of the weak acid HCN. Calculate the concentrations of H3O+, OH−, HCN, and Na+ in a solution prepared by dissolving 10.8 g of NaCN in enough water to make 5.00 × 102 mL
The ammonia complex of trimethylborane, (NH3)B(CH3)3, dissociates at 100°C to its components with Kp = 4.62 (when the pressures are in atmospheres).If NH3 is changed to some other molecule, the
The photograph below shows what occurs when a solution of potassium chromate is treated with a few drops of concentrated hydrochloric acid. Some of the bright yellow chromate ion is converted to the
The sodium salt of propanoic acid, NaCH3CH2CO2, is used as an antifungal agent by veterinarians. Calculate the equilibrium concentrations of H3O+ and OH−, and the pH, for a solution of 0.10 M
Calculate the hydronium ion concentration and pH of the solution that results when 22.0 mL of 0.15 M acetic acid, CH3CO2H, is mixed with 22.0 mL of 0.15 M NaOH.
The photographs below(a) show what occurs when a solution of iron(III) nitrate is treated with a few drops of aqueous potassium thiocyanate. The nearly colorless iron(III) ion is converted to a red
The photographs below show what occurs when you add ammonia to aqueous nickel(II) nitrate and then add ethylenediamine (NH2CH2CH2NH2) to the intermediate blue-purple solution.(a) Write a chemical
Calculate the hydronium ion concentration and the pH when 50.0 mL of 0.40 M NH3 is mixed with 50.0 mL of 0.40 M HCl.
For each of the following cases, decide whether the pH is less than 7, equal to 7, or greater than 7.(a) Equal volumes of 0.10 M acetic acid, CH3CO2H, and 0.10 M KOH are mixed.(b) 25 mL of 0.015 M
For each of the following cases, decide whether the pH is less than 7, equal to 7, or greater than 7.(a) 25 mL of 0.45 M H2SO4 is mixed with 25 mL of 0.90 M NaOH.(b) 15 mL of 0.050 M formic acid,
Decide whether each of the following statements is true or false. If false, change the wording to make it true.(a) The magnitude of the equilibrium constant is always independent of temperature.(b)
Neither PbCl2 nor PbF2 is appreciably soluble in water. If solid PbCl2 and solid PbF2 are placed in equal amounts of water in separate beakers, in which beaker is the concentration of Pb2+ greater?
Oxalic acid, H2C2O4, is a diprotic acid. Write a chemical equilibrium expression for each ionization step in water.
Sodium carbonate is a diprotic base. Write a chemical equilibrium expression for each of the two successive base reactions with water.
Characterize each of the following as product- or reactant-favored at equilibrium. (a) CO(g) + 1/2O₂(g) → CO₂(g) (b) H₂O(g) → H₂(g) + ¹/₂O₂(g) Kp = 1.2 X 1045 Kp = 9.1 X 10-41 Kp =
Prove that Ka1 × Kb2 = Kw for oxalic acid, H2C2O4, by adding the chemical equilibrium expressions that correspond to first ionization step of the acid in water with the second step of the reaction
The size of a flask containing colorless N2O4(g) and brown NO2(g) at equilibrium is rapidly reduced to half the original volume.(a) What color change (if any) is observed immediately upon halving the
Prove that Ka3 × Kb1 = Kw for phosphoric acid, H3PO4, by adding the chemical equilibrium expressions that correspond to the third ionization step of the acid in water with the first of the three
Sulfurous acid, H2SO3, is a weak acid capable of providing two H+ ions.(a) What is the pH of a 0.45 M solution of H2SO3?(b) What is the equilibrium concentration of the sulfite ion, SO32−, in the
Describe an experiment that would allow you to prove that the system 3 H2(g) + N2(g) ⇄ 2 NH3(g) is a dynamic equilibrium.
Ascorbic acid (vitamin C, C6H8O6) is a diprotic acid (Kal = 6.8 × 10−5 and Ka2 = 2.7 × 10−12). What is the pH of a solution that contains 5.0 mg of acid per milliliter of solution?
Hydrazine, N2H4, can interact with water in two steps.(a) What is the concentration of OH−, N2H5+, and N2H62+ in a 0.010 M aqueous solution of hydrazine?(b) What is the pH of the 0.010 M solution
Ethylenediamine, H2NCH2CH2NH2, can interact with water in two steps, forming OH− in each step (Appendix I). If you have a 0.15 M aqueous solution of the amine, calculate the concentrations of
Suppose a tank initially contains H2S at a pressure of 10.00 atm and a temperature of 800 K. When the reaction has come to equilibrium, the partial pressure of S2 vapor is 0.020 atm. Calculate Kp.
Pure PCl5 gas is placed in a 2.00-L flask. After heating to 250°C the pressure of PCl5 is initially 2.000 atm. However, the gas slowly but only partially decomposes to gaseous PCl3 and Cl2. When
Which should be the stronger acid, HOCN or HCN? Explain briefly. (In HOCN, the H+ ion is attached to the O atom of the OCN− ion.)
Is this compound a Brønsted acid, a Brønsted base, a Lewis acid, or a Lewis base, or some combination of these?Data given in Question 76Ethylenediamine, H2NCH2CH2NH2, can interact with water in two
Which should be the stronger Brønsted acid, [V(H2O)6]2+ or [V(H2O)6]3+?
Decide whether each of the following substances should be classified as a Lewis acid or a Lewis base.(a) H2NOH in the reaction H2NOH(aq) + HCl(aq) → [H3NOH]Cl(aq)(b) Fe2+(c) CH3NH2
Decide whether each of the following substances should be classified as a Lewis acid or a Lewis base.(a) BCl3(b) H2NNH2, hydrazine(c) The reactants in the reaction Ag+ (aq) + 2 NH3(aq) ⇒
Carbon monoxide forms complexes with low valent metals. For example, Ni(CO)4 and Fe(CO)5 are well known. CO also forms complexes with the iron(II) ion in hemoglobin, which prevents the hemoglobin
About this time, you may be wishing you had an aspirin. Aspirin is an organic acid with a Ka of 3.27 × 10−4 for the reactionIf you have two tablets, each containing 0.325 g of aspirin (mixed with
Hydrogen sulfide, H2S, and sodium acetate, NaCH3CO2, are mixed in water. Using Table 16.2, write a balanced equation for the acid–base reaction that could, in principle, occur. Does the equilibrium
Trimethylamine, (CH3)3N, is a common reagent. It interacts readily with diborane gas, B2H6. The latter dissociates to BH3, and this forms a complex with the amine, (CH3)3N→BH3. Is the BH3 fragment
Consider the following ions: NH4+, CO32−, Br−,S2−, and ClO4−.(a) Which of these ions in water gives an acidic solution and which gives a basic solution?(b) Which of these anions will have no
A 2.50-g sample of a solid that could be Ba(OH)2 or Sr(OH)2 was dissolved in enough water to make 1.00 L of solution. If the pH of the solution is 12.61, what is the identity of the solid?
In a particular solution, acetic acid is 11% ionized at 25°C. Calculate the pH of the solution and the mass of acetic acid dissolved to yield 1.00 L of solution.
The butylammonium ion, C4H9NH3+, has a Ka of 2.3 × 10−11.(a) Calculate Kb for the conjugate base, C4H9NH2 (butylamine).(b) Place the butylammonium ion and its conjugate base in Table 16.2. Name
For each of the following reactions, predict whether the equilibrium lies predominantly to the left or to the right. Explain your prediction briefly. (a) HCO3(aq) + SO4²(aq) → CO3² (aq) + HSO4
A monoprotic acid HX has Ka = 1.3 × 10−3. Calculate the equilibrium concentrations of HX and H3O+ and the pH for a 0.010 M solution of the acid.
Arrange the following 0.10 M solutions in order of increasing pH.(a) NaCl(b) NH4Cl(c) HCl(d) NaCH3CO2(e) KOH
The local anesthetic novocaine is the hydrogen chloride salt of an organic base, procaine.The pKa for novocaine is 8.85. What is the pH of a 0.0015 M solution of novocaine? C13H20N₂O2(aq)+
Pyridine is a weak organic base and readily forms a salt with hydrochloric acid.What is the pH of a 0.025 M solution of pyridinium hydrochloride, [C5H5NH+]Cl−? CH5N(aq) + HCl(aq) →→→
Nicotine, C10H14N2, has two basic nitrogen atoms (Figure 16.12), and both can react with water.Kb1 is 7.0 × 10−7 and Kb2 is 1.1 × 10−10. Calculate the approximate pH of a 0.020 M solution.Data
Saccharin (HC7H4NO3S) is a weak acid with pKa = 2.32 at 25°C. It is used in the form of sodium saccharide, NaC7H4NO3S. What is the pH of a 0.10 M solution of sodium saccharide at 25°C?
The base ethylamine (CH3CH2NH2) has a Kb of 4.3 × 10−4. A closely related base, ethanolamine (HOCH2CH2NH2), has a Kb of 3.2 × 10−5.(a) Which of the two bases is stronger?(b) Calculate the pH of
Oxalic acid is a relatively weak diprotic acid. Calculate the equilibrium constant for the reaction shown below from Kal and Ka2. (See Appendix H for the required Ka values.)Data given in Appendix H
Given the following solutions:(a) 0.1 M NH3(b) 0.1 M Na2CO3(c) 0.1 M NaCl(d) 0.1 M CH3CO2H(e) 0.1 M NH4Cl(f) 0.1 M NaCH3CO2(g) 0.1 M NH4CH3CO2(i) Which of the solutions are acidic?(ii) Which of the
For each of the following salts, predict whether a 0.10 M solution has a pH less than, equal to, or greater than 7.(a) NaHSO4(b) NH4Br(c) KClO4(d) Na2CO3(e) (NH4)2S(f) NaNO3(g) Na2HPO4(h) LiBr(i)
The equilibrium constant for the reaction of hydrochloric acid and ammonia is 1.8 × 109 (page 726). Confirm this value.Data given on Page 726The net ionic equation for the reaction of the strong
The equilibrium constant for the reaction of formic acid and sodium hydroxide is 1.8 × 1010 (page 726). Confirm this value.Data given on Page 726Consider the reaction of the naturally occurring weak
Calculate the pH of the solution that results from mixing 25.0 mL of 0.14 M formic acid and 50.0 mL of 0.070 M sodium hydroxide.
The hydrogen phthalate ion, C8H5O4−, is a weak acid with Ka = 3.91 × 10−6.What is the pH of a 0.050 M solution of potassium hydrogen phthalate, KC8H5O4? Note: To find the pH for a solution of
To what volume should 1.00 × 102 mL of any weak acid, HA, with a concentration 0.20 M be diluted to double the percentage ionization?
You prepare a 0.10 M solution of oxalic acid, H2C2O4. What molecules and ions exist in this solution? List them in order of decreasing concentration.
You mix 30.0 mL of 0.15 M NaOH with 30.0 mL of 0.15 M acetic acid. What molecules and ions exist in this solution? List them in order of decreasing concentration.
The data below compare the strength of acetic acid with a related series of acids, where the H atoms of the CH3 group in acetic acid are successively replaced by Br.(a) What trend in acid strength do
Describe an experiment that will allow you to place the following three bases in order of increasing base strength: NaCN, CH3NH2, Na2CO3.
A hydrogen atom in the organic base pyridine, C5H5N, can be substituted by various atoms or groups to give XC5H4N, where X is an atom such as Cl or a group such as CH3. The following table gives Ka
You have three solutions labeled A, B, and C. You know only that each contains a different cation—Na+, NH4+, or H3O+. Each has an anion that does not contribute to the solution pH (e.g., Cl−).
Nicotinic acid, C6H5NO2, is found in minute amounts in all living cells, but appreciable amounts occur in liver, yeast, milk, adrenal glands, white meat, and corn. Whole-wheat flour contains about
Equilibrium constants can be measured for the dissociation of Lewis acid–base complexes such as the dimethyl ether complex of BF3, (CH3)2O→BF3. The value of K (here Kp) for the reaction is 0.17
Sulfanilic acid, which is used in making dyes, is made by reacting aniline with sulfuric acid.(a) Is aniline a Brønsted base, a Lewis base, or both? Explain, using its possible reactions with HCl,
Amino acids are an important group of compounds. At low pH, both the carboxylic acid group (—CO2H) and the amine group (—NHR) are protonated. However, as the pH of the solution increases (say, by
How can water be both a Brønsted base and a Lewis base? Can water be a Brønsted acid? A Lewis acid?
The nickel(II) ion exists as [Ni(H2O)6]2+ in aqueous solution. Why is this solution acidic? As part of your answer, include a balanced equation depicting what happens when [Ni(H2O)6]2+ interacts with
The acidity of the oxoacids was described in Section 16.9, and a larger number of acids are listed in the table below.(a) What general trends do you see in these data?(b) What has a greater effect on
The halogens form three stable, weak acids, HOX.(a) Which is the strongest of these acids?(b) Explain why the acid strength changes as the halogen atom is changed. Acid pK₂ HOCI 7.46 HOBr 8.7 HOI
Perchloric acid behaves as an acid, even when it is dissolved in sulfuric acid.(a) Write a balanced equation showing how perchloric acid can transfer a proton to sulfuric acid.(b) Draw a Lewis
You purchase a bottle of water. On checking its pH, you find that it is not neutral, as you might have expected. Instead, it is slightly acidic. Why?
Uracil is a base found in RNA. Indicate sites in the molecule where hydrogen bonding is possible or that are sites of Lewis basicity. H H N :0: || C N 1 C. H Uracil
Chemists often refer to the degree of ionization of a weak acid or base and give it the symbol α. The equilibrium constant in terms of α and Co, the initial acid or base concentration, is given by
Exploring the degree of ionization equation in Study Question 127: Calculate the degree of ionization, α, for formic acid at the following concentrations: 0.0100 M, 0.0200 M, 0.0400 M, 0.100 M,
Consider a salt of a weak base and a weak acid such as ammonium cyanide. Both the NH4+ and CN− ions interact with water in aqueous solution, but the net reaction can be considered as a proton
Does the pH of the solution increase, decrease, or stay the same when you(a) Add solid ammonium chloride to a dilute aqueous solution of NH3?(b) Add solid sodium acetate to a dilute aqueous solution
Does the pH of the solution increase, decrease, or stay the same when you(a) Add solid sodium oxalate, Na2C2O4, to 50.0 mL of 0.015 M oxalic acid, H2C2O4?(b) Add solid ammonium chloride to 75 mL of
What is the pH of a solution that consists of 0.20 M ammonia, NH3, and 0.20 M ammonium chloride, NH4Cl?
What is the pH of 0.15 M acetic acid to which 1.56 g of sodium acetate, NaCH3CO2, has been added?
What is the pH of the solution that results from adding 30.0 mL of 0.015 M KOH to 50.0 mL of 0.015 M benzoic acid?
What is the pH of the solution that results from adding 25.0 mL of 0.12 M HCl to 25.0 mL of 0.43 M NH3?
What is the pH of the buffer solution that contains 2.2 g of NH4Cl in 250 mL of 0.12 M NH3? Is the final pH lower or higher than the pH of the 0.12 M ammonia solution?
Lactic acid (CH3CHOHCO2H) is found in sour milk, in sauerkraut, and in muscles after activity. (Ka for lactic acid = 1.4 × 10−4.)(a) If 2.75 g of NaCH3CHOHCO2, sodium lactate, is added to 5.00 ×
What mass of sodium acetate, NaCH3CO2, must be added to 1.00 L of 0.10 M acetic acid to give a solution with a pH of 4.50?
What mass of ammonium chloride, NH4Cl, must be added to exactly 5.00 × 102 mL of 0.10 M NH3 solution to give a solution with a pH of 9.00?
Calculate the pH of a solution that has an acetic acid concentration of 0.050 M and a sodium acetate concentration of 0.075 M.
Calculate the pH of a solution that has an ammonium chloride concentration of 0.050 M and an ammonia concentration of 0.045 M.
What must the ratio of acetic acid to acetate ion be to have a buffer with a pH value of 5.00?
What must the ratio of H2PO4− to HPO42− be to have a buffer with a pH value of 7.00?
A buffer is composed of formic acid and its conjugate base, the formate ion.(a) What is the pH of a solution that has a formic acid concentration of 0.050 M and a sodium formate concentration of
A buffer solution is composed of 1.360 g of KH2PO4 and 5.677 g of Na2HPO4.(a) What is the pH of the buffer solution?(b) What mass of KH2PO4 must be added to decrease the buffer solution pH by 0.50
Which of the following combinations would be the best to buffer the pH of a solution at approximately 9?(a) HCl and NaCl(b) NH3 and NH4Cl(c) CH3CO2H and NaCH3CO2
Which of the following combinations would be the best to buffer the pH of a solution at approximately 7?(a) H3PO4 and NaH2PO4(b) NaH2PO4 and Na2HPO4(c) Na2HPO4 and Na3PO4
Describe how to prepare a buffer solution from NaH2PO4 and Na2HPO4 to have a pH of 7.5.
Describe how to prepare a buffer solution from NH3 and NH4Cl to have a pH of 9.5.
Determine the volume (in mL) of 1.00 M NaOH that must be added to 250 mL of 0.50 M CH3CO2H to produce a buffer with a pH of 4.50.
Determine the volume (in mL) of 1.00 M HCl that must be added to 750 mL of 0.50 M HPO42− to produce a buffer with a pH of 7.00.
A buffer solution was prepared by adding 4.95 g of sodium acetate, NaCH3CO2, to 2.50 × 102 mL of 0.150 M acetic acid, CH3CO2H.(a) What is the pH of the buffer?(b) What is the pH of 1.00 × 102 mL of
You dissolve 0.425 g of NaOH in 2.00 L of a buffer solution that has [H2PO4−] = [HPO42−] =0.132 M. What is the pH of the solution before adding NaOH? After adding NaOH?
A buffer solution is prepared by adding 0.125 mol of ammonium chloride to 5.00 × 102 mL of 0.500 M solution of ammonia.(a) What is the pH of the buffer?(b) If 0.0100 mol of HCl gas is bubbled into
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