Questions and Answers of Elementary Principles Chemical

Suppose that 0.010 0 M Mn2+ is titrated with 0.005 00 M EDTA at pH 7.00.(a) What is the concentration of free Mn2+ at the equivalence point?(b) What is the quotient [H3Y-]/[H2Y2-] in the solution
Calculate the concentration of H2Y2- at the equivalence point in Exercise 11-C.Exercise 11-CCalculate pCu2+ (to the 0.01 decimal place) at each of the following points in the titration of 50.0 mL of
Calculate pCu2+ (to the 0.01 decimal place) at each of the following points in the titration of 50.0 mL of 0.040 0 M EDTA with 0.080 0 M Cu(NO3)2 at pH 5.00: 0.1, 5.0, 10.0, 15.0, 20.0, 24.0, 25.0,
A 25.00-mL sample containing Fe3[1] and Cu2+ required 16.06 mL of 0.050 83 M EDTA for complete titration. A 50.00-mL sample of the unknown was treated with NH4F to protect the Fe3+. Then Cu2+ was
Potassium ion in a 250.0 (±0.1) mL water sample was precipitated with sodium tetraphenylborate:The precipitate was filtered, washed, dissolved in an organic solvent, and treated with excess
Effect of concentration in the titration of weak acid with strong base. Use your spreadsheet from Problem 10-65 to prepare a family of titration curves for pKa = 6, with the following combinations of
Effect of pKa in the titration of weak acid with strong base. Use Equation 10-13 to compute and plot the family of curves at the left side of Figure 10-3. For a strong acid, choose a large Ka, such
How many grams of potassium hydrogen phthalate should be weighed into a flask to standardize ~0.05 M NaOH if you wish to use ~30 mL of base for the titration?
Explain how to use potassium hydrogen phthalate to standardize a solution of NaOH.
Why is it more accurate to use a primary standard with a high equivalent mass (the mass required to provide or consume 1 mol of H+) than one with a low equivalent mass?
(a) What is the pH at the equivalence point when 0.030 0 M NaF is titrated with 0.060 0 M HClO4?(b) Why would an indicator end point probably not be useful in this titration?
Would the indicator bromocresol green, with a transition range of pH 3.8–5.4, ever be useful in the titration of a weak acid with a strong base?
Cresol red has two transition ranges listed in Table 10-3. What color would you expect it to be at the following pH values?(a) 0;(b) 1;(c) 6;(d) 9Table 10-3 Acid color Transition Base Indicator range
What color do you expect to observe for cresol purple indicator (Table 10-3) at the following pH values?(a) 1.0;(b) 2.0;(c) 3.0Table 10-3 Acid color Transition Base Indicator range (pH) color
What color do you expect to observe for cresol purple indicator (Table 10-3) at the following pH values?(a) 1.0;(b) 2.0;(c) 3.0Table 10-3 Acid color Transition Base Indicator range (pH) color
Consider the titration in Figure 10-2, for which the pH at the equivalence point is calculated to be 9.25. If thymol blue is used as an indicator, what color will be observed through most of the
Write the formula of a compound with a negative pKa.
Explain the origin of the rule of thumb that indicator color changes occur at pKHIn ± 1.
What is a Gran plot used for?
Why is the equivalence-point pH necessarily below 7 when a weak base is titrated with strong acid?
When 22.63 mL of aqueous NaOH were added to 1.214 g of cyclohexylaminoethanesulfonic acid (FM 207.29, structure in Table 8-2) dissolved in 41.37 mL of water, the pH was 9.24. Calculate the molarity
Find the equilibrium constant for the reaction of MES (Table 8-2) with NaOH.Table 8-2 A(pKa/AT (K) Formula Name Structure u = 0.1 M mass CH,CO,H H,NCCH,NH - (CO,H) 1.59 190.15
Find the equilibrium constant for the reaction of MES (Table 8-2) with NaOH.
Calculate the pH when 25.0 mL of 0.020 0 M 2-aminophenol have been titrated with 10.9 mL of 0.015 0 M HClO4.
Calculate the pH of a solution made by mixing 50.00 mL of 0.100 M NaCN with(a) 4.20 mL of 0.438 M HClO4(b) 11.82 mL of 0.438 M HClO4(c) What is the pH at the equivalence point with 0.438 M HClO4?
Why is it not practical to titrate an acid or a base that is too weak or too dilute?
Spectrophotometry with indicators.† Acid-base indicators are themselves acids or bases. Consider an indicator, HIn, which dissociates according to the equationThe molar absorptivity, ε, is 2 080
Indicator error. Consider the titration in Figure 10-2 in which the equivalence-point pH in Table 10-2 is 9.25 at a volume of 10.00 mL.(a) Suppose you used the yellow-to-blue transition of thymol
Finding the end point from pH measurements. Here are data points around the second apparent end point in Figure 10-5:(a) Prepare a spreadsheet or table analogous to Figure 10-6, showing the first and
A 0.100 M solution of the weak acid HA was titrated with 0.100 M NaOH. The pH measured when Vb = ½ Ve was 4.62. Using activity coefficients, calculate pKa. The size of the A- anion is 450 pm.
When 100.0 mL of a weak acid were titrated with 0.093 81 M NaOH, 27.63 mL were required to reach the equivalence point. The pH at the equivalence point was 10.99. What was the pH when only 19.47 mL
Select indicators from Table 10-3 that would be useful for the titrations in Figures 10-1 and 10-2 and the pKa = 8 curve in Figure 10-3. Select a different indicator for each titration and state what
Select indicators from Table 10-3 that would be useful for the titrations in Figures 10-1 and 10-2 and the pKa = 8 curve in Figure 10-3. Select a different indicator for each titration and state what
Write the chemical reactions (including structures of reactants and products) that occur when the amino acid histidine is titrated with perchloric acid. (Histidine is a molecule with no net charge.)
Consider the titration of 50.0 mL of 0.050 0 M malonic acid with 0.100 M NaOH. Calculate the pH at each point listed and sketch the titration curve: Vb = 0.0, 8.0, 12.5, 19.3, 25.0, 37.5, 50.0, and
Calculate the pH at each point listed for the titration of 100.0 mL of 0.100 M cocaine (Section 8 4, Kb = 2.6 × 10-6) with 0.200 M HNO3. The points to calculate are Va = 0.0, 10.0, 20.0, 25.0, 30.0,
Calculate the pH at each point listed for the titration of 50.0 mL of 0.050 0 M formic acid with 0.050 0 M KOH. The points to calculate are Vb = 0.0, 10.0, 20.0, 25.0, 30.0, 40.0, 45.0, 48.0, 49.0,
Calculate the pH at each of the following points in the titration of 50.00 mL of 0.010 0 M NaOH with 0.100 M HCl. Volume of acid added: 0.00, 1.00, 2.00, 3.00, 4.00, 4.50, 4.90, 4.99, 5.00, 5.01,
Explain what is wrong with the following statement: At its isoelectric point, the charge on all molecules of a particular protein is 0.
Fractional composition in a triprotic system. For a triprotic system, the fractional composition equations arewhere D = [H+]3 + K1[H+]2 + K1K2[H+] + K1K2K3. Use these equations to create a fractional
Fractional composition in a diprotic system. Create a spreadsheet with Equations 9-19 through 9-21 to compute the three curves in Figure 9-4. Plot the three curves in a beautifully labeled
Calculate αH2A, αHA-, αA2- and for cis-butenedioic acid at pH 1.00, 1.92, 6.00, 6.27, and 10.00.
What fraction of ethane-1,2-dithiol is in each form (H2A, HA+, A2+) at pH 8.00? at pH 10.00?
Draw the structure of the predominant form of pyridoxal-5-phosphate at pH 7.00.
Starting with the fully protonated species, write the stepwise acid dissociation reactions of the amino acids glutamic acid and tyrosine. Be sure to remove the protons in the correct order. Which
We will abbreviate malonic acid, CH2(CO2H)2, as H2M. Find the pH and concentrations of H2M, HM+, and M2+ in (a) 0.100 M H2M; (b) 0.100 M NaHM; (c) 0.100 M Na2M.
Neutral lysine can be written HL. The other forms of lysine are H3L2+, H2L+, and L+. The isoelectric point is the pH at which the average charge of lysine is 0. Therefore, at the isoelectric point,
Calculate the isoionic pH of 0.010 M lysine.
Draw the structures of the predominant forms of glutamic acid and tyrosine at pH 9.0 and pH 10.0. What is the second most abundant species at each pH?
(a) Draw the structure of the predominant form (principal species) of 1,3-dihydroxybenzene at pH 9.00 and at pH 11.00.(b) What is the second most prominent species at each pH?(c) Calculate the
Calculate the pH of a 0.010 M solution of each amino acid in the form drawn here. H2N NH2 NH2 NH C=0 CH2 CH2 S CH, CH, CH2 CH2 (a) H;NCHCO, (b) H&NCHCO, (c) H,NCHCO, Glutamine Cysteine Arginine
How many milliliters of 0.800 M KOH should be added to 5.02 g of 1,5-pentanedioic acid (C5H8O4, FM 132.11) to give a pH of 4.40 when diluted to 250 mL?
(a) How many grams of NaHCO3 (FM 84.007) must be added to 4.00 g of K2CO3 (FM 138.206) to give a pH of 10.80 in 500 mL of water?(b) What will be the pH if 100 mL of 0.100 M HCl are added to the
Find the pH and the concentrations of H2SO3, HSO3-, and SO32- in each solution:(a) 0.050 M H2SO3;(b) 0.050 M NaHSO3;(c) 0.050 M Na2SO3.
Covalent compounds generally have higher vapor pressure than ionic compounds. The “fishy” smell of fish arises from amines in the fish. Explain why squeezing lemon (which is acidic) onto fish
Using activity coefficients, find the pH and fraction of dissociation of 50.0 mM hydroxybenzene (phenol) in 0.050 M LiBr. Take the size of C6H5O- to be 600 pm.
Calculate the pH of (a) 1.0 × 10-3 M HBr; (b) 1.0 × 10-2 M KOH.
Why doesn’t water dissociate to produce 10-7 M H+ and 10-7M OH- when some HBr is added?
Use the Goal Seek spreadsheet at the end of the chapter to find the pH of 1.00 L of solution containing 0.030 mol HA (pKa = 2.50) and 0.015 mol NaA. What would the pH be with the approximations [HA]
A solution with an ionic strength of 0.10 M containing 0.010 0 M phenylhydrazine has a pH of 8.13. Using activity coefficients correctly, find pKa for the phenylhydrazinium ion found in
(a) Find the pH of a solution prepared by dissolving 1.00 g of glycine amide hydrochloride (Table 8-2) plus 1.00 g of glycine amide in 0.100 L.(b) How many grams of glycine amide should be added to
Find the pH of a solution prepared by dissolving 1.00 g of glycine amide hydrochloride (Table 8-2) plus 1.00 g of glycine amide in 0.100 L. Glycine amide C;H&N20 H,N. FM 74.08 NH,
A solution contains 63 different conjugate acid-base pairs. Among them is acrylic acid and acrylate ion, with the equiliborium ratio [acrylate]/[acrylic acid] = 0.75. What is the pH of the solution?
A solution contains 63 different conjugate acid-base pairs. Among them is acrylic acid and acrylate ion, with the equiliborium ratio [acrylate]/[acrylic acid] = 0.75. What is the pH of the solution?
Which of the following bases would be most suitable for preparing a buffer of pH 9.00?(i) NH3 (ammonia, Kb = 1.76 × 10-5);(ii) C6H5NH2 (aniline, Kb = 3.99 ×10-10);(iii) H2NNH2 (hydrazine, Kb = 1.05
The pH of 0.10 M ethylamine is 11.82.(a) Without referring to Appendix G, find Kb for ethylamine.(b) Using results from part (a), calculate the pH of 0.10 M ethylammonium chloride.
Find the pH of 0.050 M sodium butanoate (the sodium salt of butanoic acid, also called butyric acid).
Calculate the limiting value of the fraction of dissociation (α) of a weak acid (pKa = 5.00) as the concentration of HA approaches 0. Repeat the same calculation for pKa = 9.00.
The pH of 0.010 M o-cresol is 6.16. Find pKa for this weak acid. CH, o-Cresol ОН
What is the pH of a solution prepared by dissolving 1.23 g of 2-nitrophenol (FM 139.11) in 0.250 L?
(Without activities), calculate the pH of(a) 1.0 × 10-8 M HBr(b) 1.0 × 10-8 M H2SO4 (H2SO4 dissociates completely to 2H+plus SO24- at this low concentration.)
Using activity coefficients correctly, find the pH of 1.0 × 10-2 M NaOH.
Heterogeneous equilibria and calcite solubility. If river water in Box 7-2 is saturated with calcite (CaCO3), [Ca2+] is governed by the following equilibria:(a) From these reactions, find the
Use the systematic treatment of equilibrium to find the concentrations of the major species in a saturated aqueous solution of LiF. Consider these reactions:(a) Initially, set the ionic strength to 0
Use the systematic treatment of equilibrium to find the concentrations of the major species in a saturated aqueous solution of LiF. Consider these reactions: LiF(s) = Li* +F Ksp = [Li*]YLi+[F¯]YF
Look up the equilibrium constant for the ion-pairing reaction in Appendix J.(a) Use the systematic treatment of equilibrium to find [Zn2+] in 0.010 F ZnSO4. Neglect activity coefficients and
(a) Following the example of Mg(OH)2 in Section 7-5, write the equations needed to find the solubility of Ca(OH)2. Include activity coefficients where appropriate. Equilibrium constants are in
For a 0.1 M aqueous solution of sodium acetate, Na+CH3CO-2, one mass balance is simply [Na+] = 0.1 M. Write a mass balance involving acetate.
Write the charge balance for a solution of H2SO4 in water if H2SO4 ionizes to HSO‑4 and SO24-.
Why do activity coefficients not appear in the charge and mass balance equations?
The equilibrium constant for dissolution in water of a nonionic compound, such as diethyl ether (CH3CH2OCH2CH3), can be writtenAt low ionic strength, γ = 1 for neutral compounds. At high ionic
Calculate the activity coefficient of Al3+ when µ = 0.083 M by linear interpolation in Table 7-1.Table 7-1 Ion size Ionic strength (p. M) Ion (a, pm) 0.001 0.005 0.01 0.05 0.1 Charge = +1 H*
Which statements are true? In the ionic strength range 0–0.1 M, activity coefficients decrease with(a) Increasing ionic strength;(b) Increasing ionic charge;(c) Decreasing hydrated radius.
Explain why the solubility of an ionic compound increases as the ionic strength of the solution increases (at least up to ~ 0.5 M).
Using activities, find the concentrations of the major species in 0.10 M NaClO4 saturated with Mn(OH)2. Take the ionic strength to be 0.10 M and suppose that the ion size of MnOH+ is the same as
Write charge and mass balances for aqueous Ca3(PO4)2 if the species are Ca2+, CaOH+, CaPO-4, PO3-4, HPO24-, H2PO-4, and H3PO4.
Write the charge and mass balances for dissolving CaF2 in water if the reactions are CaF,(8) = Ca2+ + 2F Ca?+ + H,O = CAOH+ + H* Ca2+ + F = CaF+ CaF2(s) = CaF2(aq) F + H* = HF(aq) HF(aq) + F = HF,
(a) Write the mass balance for CaCl2 in water if the species are Ca2+ and Cl-.(b) Write the mass balance if the species are Ca2+, Cl-, CaCl-, and CaOH+.(c) Write the charge balance for part (b).
Write the mass balance for CaCl2 in water if the species are Ca2+ and Cl-.(b) Write the mass balance if the species are Ca2+, Cl-, CaCl-, and CaOH+.(c) Write the charge balance for part (b).
A 40.0-mL solution of 0.040 0 M Hg2(NO3) 2 was titrated with 60.0 mL of 0.100 M KI to precipitate Hg2I2 (Ksp = 4.6 × 10-29).(a) Show that 32.0 mL of KI are needed to reach the equivalence
Using activities, calculate the pH and concentration of H+ in 0.050 M LiBr at 25°C.
Using activities, calculate the pH and concentration of H+ in 0.050 M LiBr at 25 C.
Using activities, find [Ag+] in 0.060 M KSCN saturated with AgSCN(s).
Find the activity (not the activity coefficient) of the (C3H7)4N+ (tetrapropylammonium) ion in a solution containing 0.005 0 M (C3H7)4N+Br- plus 0.005 0 M (CH3)4N+Cl-.
Assuming complete dissociation of the salts, calculate the ionic strength of(a) 0.2 mM KNO3;(b) 0.2 mM Cs2CrO4;(c) 0.2 mM MgCl2 plus 0.3 mM AlCl3.
From the following equilibrium constants, calculate the equilibrium constant for the reaction HO,CCO,H 2H* + C,0.
(a) Using only Ksp from Table 6-3, calculate how many moles of Ca(OH)2 will dissolve in 1.00 L of water.(b) How will the solubility calculated in part (a) be affected by the K1 reaction in Table
Write the Ka2 reaction of phosphoric acid (H3PO4) and the Kb2 reaction of disodium oxalate (Na2C2O4).
Write the Kb reaction of CN-. Given that the Ka value for HCN is 6.2 × 10-10, calculate Kb for CN-.
Which is a stronger acid, (a) or (b)? (a) (b) Cl,HCCOH СІН,ССОН Dichloroacetic acid Chloroacetic acid K = 8 x 10-2 K = 1.36 x 10-3 Which is a stronger base, (c) or (d)? (c) (d) H,NNH,

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