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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
The cumulative formation constant for SnCl2(aq) in 1.0 M NaNO3 is β2 = 12. Find the concentration of SnCl2(aq) for a solution in which the concentrations of Sn2+ and Cl- are both somehow fixed at
Given the following equilibria, calculate the concentration of each zinc species in a solution saturated with Zn(OH)2(s) and containing [OH-] at a fixed concentration of 3.2 × 10-7M. Zn(OH)2(s) Ksp
Although KOH, RbOH, and CsOH have little association between metal and hydroxide in aqueous solution, Li+ and Na+ doform complexes with OH-: Na + + OH- ⇌ NaoH (aq) K1 =
In Figure 6-3, the concentration of PbI2(aq) is independent of PbI2(aq) is independent of [I-]. Use any of the equilibrium constants for Reactions 6-11 through 6-15 to find the equilibrium constant
Distinguish Lewis acids and bases from Bronsted-Lowry acids and bases. Give an example of each.
Fill in the blanks: (a) The product of a reaction between a Lewis acid and a Lewis base is called ________. (b) The bond between a Lewis acid and a Lewis base is called ________ or _______. (c)
Explain the statement that predictions about the direction of a reaction based on Gibbs free energy or Le Châtelier's principle are thermodynamic, not kinetic.
Why is the pH of distilled water usually 7? How can you prevent this from happening?
Use electron dot structures to show why tetramethylammonium hydroxide, (CH3)4N+OH-, is an ionic compound. That is, show why hydroxide is not covalently bound to the rest of the molecule.
Identify the conjugate acid-base pairs in the following reactions:ab.
Calculate [H+] and pH for the following solutions: (a) 0.010 MHNO3 (b) 0.035 MKOH (c) 0.030 M HCl (d) 3.0 M HCl (e) 0.010 M [(CH3)4N+OH- Tetramethylammonium hydroxide
Use Table 6-1 to calculate the pH of pure water at (a) 25°C and (b) 100°C.
An acidic solution containing 0.010 M La3+ is treated with NaOH until La(OH)3 precipitates. At what pH does this occur?
Use Le Châtelier's principle and Kw in Table 6-1 to decide whether the autoprotolysis of water is endothermic or exothermic at (a) 25°C; (b) 100°C; (c) 300°C.
Write the formulas and names for three classes of weak acids and two classes of weak bases.
Write the Ka reaction for trichloroacetic acid, Cl3CCO2H, for anilinium ion,and for lanthanum ion, La3+,
Write the Kb reactions for pyridine and for sodium 2 - mercap - toethanol.
Write the Ka and Kb reactions of NaHCO3.
Write the stepwise acid-base reactions for the following ions in water. Write the correct symbol (for example, Kb1) for the equilibrium constant for each reaction.a.b.
For the reaction 2A(g) + B(aq) + 3C(l) ⇌ D(s) + 3E(g), the concentrations at equilibrium are found to be A: 2.8 × 103 pa B: 1.2 × 10-2 M C: 12.8 M D:16.5M E:3.6 × 104 Torr Find the numerical
From the Kb values for phosphate in Equations 6-32 through 6-34, calculate the three Ka values of phosphoric acid.
(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 6-3?
The planet Aragonose (which is made mostly of the mineral aragonite, whose composition is CaCO3) has an atmosphere containing methane and carbon dioxide, each at a pressure of 0.10 bar. The oceans
From the equations HOCI ⇌ H+ + OCI- K = 3.0 × 10-8 HOCI + OBr- ⇌ HOBr + OCI- K = 15 find the value of K for the reaction ⇌ HOBr = H+ + OBr-.
The formation of tetrafluoroethylene from its elements is highly exothermic:(a) If a mixture of F2, graphite, and C2F4 is at equilibrium in a closed container, will the reaction go to the right or to
Including activity coefficients, find the concentration of Ba2+ in a 0.100 M (CH3)4NIO3 solution saturated with Ba(IO3)2.
Find the activity coefficient of H+ in a solution containing 0.010 M HCl plus 0.040 M KClO4. What is the pH of the solution?
Using activities, calculate the pH of a solution containing 0.010M NaOH plus 0.0120 M LiNO3. What would be the pH if you neglected activities?
The temperature-dependent form of the extended Debye- Hückel equation 7-6 iswhere is the (dimensionless) dielectric constant of water, T is temperature (K), z is the charge
Extended Debye-Hückel equation. Use Equation 7-6 to calculate the activity coefficient (γ) as a function of ionic strength (μ) for μ = 0.0001, 0.0003, 0.001, 0.003, 0.01, 0.03, and 0.1 M. (a) For
Activity coefficient of a neutral molecule. We use the approximation that the activity coefficient (γ) of neutral molecules is 1.00. A more accurate relation is log γ =
State the meaning of the charge and mass balance equations.
Write the charge balance for a solution containing H+, OH-, Ca2+, HCO-3, CO23-,Ca(HCO3)+,Ca(OH)+, K+, and CIO-4
Write the charge balance for an aqueous solution of arsenic acid, H3AsO4, in which the acid can dissociate to H2AsO4- , HAsO24- , and AsO43-. Look up the structure of arsenic acid in Appendix G and
(a) Write the charge and mass balances for a solution made by dissolving MgBr2 to give Mg2+, Br-, MgBr+, and MgOH+. (b) Modify the mass balance if the solution was made by dissolving 0.2 mol MgBr2 in
What would happen if charge balance did not exist in a solution? The force between two charges is given in the footnote on this page. Find the force between two beakers separated by 1.5 m of air if
Consider the dissolution of the compound X2Y3, which gives X2Y22+, X2Y4+, X2Y3(aq), and Y2-. Use the mass balance to find an expression for [Y2-] in terms of the other concentrations. Simplify your
Write a mass balance for a solution of Fe2(SO4)3 if the species are Fe3+ , Fe(OH)2 , Fe(OH)+2 , Fe2(OH)4+2 , FeSO+4 , , and SO2-4 . andHSO2-
(a) Following the example of ammonia in Section 7-5, write the equilibria and charge and mass balances needed to find the composition of 0.01 M sodium acetate, which you should abbreviate as Na+A-.
Calculate the ionic strength of (a) 0.0087 M KOH and (b) 0.0002 M La(IO3)3 (assuming complete dissociation at this low concentration and no hydrolysis reaction to make LaOH2+).
Find the activity coefficient of each ion at the indicated ionic strength: (a) SO24- (μ = 0.01 M) (b) Sc3+ (μ = 0.005 M) (c) Eu3+ (μ = 0.1 M) (d) (CH3CH2)3NH+ (μ = 0.05 M)
Interpolate in Table 7-1 to find the activity coefficient of H+ when μ = 0.030M.
Calculate the activity coefficient of Zn2+ when μ = 0.083M by using (a) Equation 7-6; (b) linear interpolation in Table 7-1.
Including activity coefficients, find [Hg22+] in saturated Hg2Br2 in 0.001 00 M KBr.
Why doesn't water dissociate to produce 10 -7 M H+ and 10-7 MOH- when some HBr is added?
When is a weak acid weak and when is a weak acid strong? Show that the weak acid HA will be 92% dissociated when dissolved in water if the formal concentration is one-tenth of Ka (F = Ka/10). Show
A 0.045 0 M solution of benzoic acid has a pH of 2.78. Calculate pKa for this acid.
A 0.0450 M solution of HA is 0.60% dissociated. Calculate pKa for this acid.
Barbituric acid dissociates as follows:(a) Calculate the pH and fraction of dissociation of 102.00 M barbituric acid. (b) Calculate the pH and fraction of dissociation of 1010.00 M barbituric acid.
Extended Debye-Hückel equation. Use Equation 7-6 to calculate the activity coefficient (γ) as a function of ionic strength (μ) for μ = 0.0001, 0.000 3, 0.001, 0.003, 0.01, 0.03, and 0.1 M. (a)
Cr3+ is acidic by virtue of the hydrolysis reaction[Further reactions produce Cr(OH)+2, Cr(OH)3, and Cr(OH)-4.] Find the value of Ka1 in Figure 6-8. Considering only the Ka1 reaction, find the pH of
From the dissociation constant of HNO3 at 25°C in Box 8-1, find the percent dissociated in 0.100 M HNO3 and in 1.00 M HNO3.
Solve the equation x2/(F - x) = K by using Goal Seek. Guess a value of x in cell A4 and evaluate x2/(F - x) in cell B4. Use Goal Seek to vary the value of x until x2/(F - x) is equal to K. Use your
Find the pH and fraction of association (α) of a 0.100 M solution of the weak base B with Kb = 1.00 × 10-5.
Calculate the pH of (a) 1.0 × 10-3 M HBr; (b) 1.0 × 10-2 M KOH.
Find the pH and concentrations of (CH3)3N and (CH3)3NH+ in a 0.060 M solution of trimethylamine.
Find the pH of 0.050 M NaCN.
Calculate the fraction of association (α) for 1.00 × 10-1, 1.00 × 10-2, and 1.00 1012 M sodium acetate. Does increase or decrease with dilution?
A 0.10 M solution of a base has pH = 9.28. Find Kb.
A 0.10 M solution of a base is 2.0% hydrolyzed (α = 0.020). Find Kb.
Show that the limiting fraction of association of a base in water, as the concentration of base approaches 0, is α = 107 Kb/ (1 + 107Kb). Find the limiting value of for Kb = 10-4 and for Kb =
Describe how to prepare 100 mL of 0.200 M acetate buffer, pH 5.00, starting with pure liquid acetic acid and solutions containing ~3 M HCl and ~3 M NaOH.
Why is the pH of a buffer nearly independent of concentration?
Why does buffer capacity increase as the concentration of buffer increases?
Why does buffer capacity increase as a solution becomes very acidic (pH ≈ 1) or very basic (pH ≈ 13)?
Calculate the pH of 5.0 × 10-8 M HClO4. What fraction of the total H+ in this solution is derived from dissociation of water?
Why does the buffer capacity reach a maximum when pH = pKa?
Explain the following statement: The Henderson-Hasselbalch equation (with activity coefficients) is always true; what may not be correct are the values of [A-] and [HA] that we choose to use in the
Which of the following acids would be most suitable for preparing a buffer of pH 3.10? (i) hydrogen peroxide; (ii) propanoic acid; (iii) cyanoacetic acid; (iv) 4 - aminobenzenesulfonic acid.
A buffer was prepared by dissolving 0.100 mol of the weak acid HA (Ka = 1.00 × 10 -5) plus 0.050 mol of its conjugate base Na+A- in 1.00 L. Find the pH.
Write the Henderson-Hasselbalch equation for a solution of formic acid. Calculate the quotient [HCO-2 ]/[HCO2H] at (a) pH 3.000; (b) pH 3.744; (c) pH 4.000.
Calculate the quotient [HCO-2 ]/[HCO2H] at pH 3.744 if the ionic strength is 0.1 M by using the effective equilibrium constant listed for μ = 0.1 in 0.1 in Appendix G.
Given that pKb for nitrite ion (NO-2 ) is 10.85, find the quotient [HNO2]/[NO-2 ] in a solution of sodium nitrite at (a) pH 2.00; (b) p 10.00.
(a) Would you need NaOH or HCl to bring the pH of 0.050 0 M HEPES (Table 8-2) to 7.45? (b) Describe how to prepare 0.250 L of 0.050 0 M HEPES, pH 7.45.
How many milliliters of 0.246 M HNO3 should be added to 213 mL of 0.00666 M 2,2' bipyridine to give a pH of 4.19?
(a) Write the chemical reactions whose equilibrium constants are Kb and Ka for imidazole and imidazole hydrochloride, respectively.
(a) The measured pH of 0.100 M HCl at 25°C is 1.092. From this information, calculate the activity coefficient of H+ and compare your answer with that in Table 7-1.
Calculate the pH of a solution prepared by mixing 0.0800 mol of chloroacetic acid plus 0.0400 mol of sodium chloroacetate in 1.00 L of water.(a) First do the calculation by assuming that the
Calculate how many milliliters of 0.626 M KOH should be added to 5.00 g of MOBS (Table 8-2) to give a pH of 7.40.
(a) Use Equations 8-20 and 8-21 to find the pH and concentrations of HA and A- in a solution prepared by mixing 0.00200 mol of acetic acid plus 0.004 00 mol of sodium acetate in 1.00 L of water.(b)
(a) Calculate the pH of a solution prepared by mixing 0.0100 mol of the base B (Kb = 10 = - 2.00) with 0.020 0 mol of BH+Br- and diluting to 1.00 L. First calculate the pH by assuming [B] = 0.0100
Effect of ionic strength on pKa. Ka for the H2PO4- /HPO24- buffer isIf you mix a 1:1 mole ratio of H2PO-4 and HPO42- at 0 ionic strength, the pH is 7.20. Using activity coefficients from Table 7-1,
Systematic treatment of equilibrium. The acidity of Al3+ is determined by the following reactions. Write the equations needed to find the pH of Al(ClO4)3 at a formal concentration F.
Write the chemical reaction whose equilibrium constant is (a) Ka for benzoic acid, C6H5CO2H (b) Kb for benzoate ion, C6H5CO-2 (c) Kb for aniline, C6H5NH2 (d) Ka for anilinium ion, C6H5NH+3
Find the pH and fraction of dissociation (α) of a 0.100 M solution of the weak acid HA with Ka = 1.00 × 10-5.
BH+ ClO-4 is a salt formed from the base B (Kb = 1.00 × 10-4) and perchloric acid. It dissociates into BH+, a weak acid, and ClO-4, which is neither an acid nor a base. Find the pH of 0.100 M
Find the pH and concentrations of (CH3)3N and (CH3)3NH+ in a 0.060 M solution of trimethylammonium chloride.
Use the reaction quotient, Q, to explain why the fraction of dissociation of weak acid, HA, increases when the solution is diluted by a factor of 2.
Consider HA-, the intermediate form of a diprotic acid. Ka for this species is 10-4 and Kb is 10-8. Nonetheless, the Ka and Kb reactions proceed to nearly the same extent when NaHA is dissolved in
Derivation of Equation 9-10 for pH of the intermediate form Na+ HA-. The derivation in the chapter was for HL, the intermediate form of H2L+. Write the mass and charge balances for Na+ HA- at formal
Heterogeneous equilibrium. CO2 dissolves in water to give "carbonic acid" (which is mostly dissolved CO2, as described in Box 6-4).CO2(g) ⇌ CO2(aq) K = 10-1.5(The equilibrium constant is called
Effect of temperature on carbonic acid acidity and the solubility of CaCO3.9Box 9-1 states that marine life with CaCO3 shells and skeletons will be threatened with extinction in cold polar waters
How many grams of Na2CO3 (FM 105.99) should be mixed with 5.00 g of NaHCO3 (FM 84.01) to produce 100 mL of buffer with pH 10.00?
How many milliliters of 0.202 M NaOH should be added to 25.0 mL of 0.0233 M salicylic acid (2-hydroxybenzoic acid) to adjust the pH to 3.50?
Describe how you would prepare exactly 100 mL of 0.100 M picolinate buffer, pH 5.50. Possible starting materials are pure picolinic acid (pyridine-2-carboxylic acid, FM 123.11), 1.0 M HCl, and 1.0 M
How many grams of Na2SO4 (FM 142.04) should be added to how many grams of sulfuric acid (FM 98.08) to give 1.00 L of buffer with pH 2.80 and a total sulfur ( = SO24 + HSO-4 + H2SO4) concentration of
Phosphate at 0.01 M is one of the main buffers in blood plasma, whose pH is 7.45. Would phosphate be as useful if the plasma pH were 8.5?
(a) Calculate the quotient [H3PO4]/[H2PO4-] in 0.0500 M KH2PO4. (b) Find the same quotient for 0.0500 M K2HPO4.
Write the general structure of an amino acid. Why do some amino acids in Table 9-1 have two pK values and others three?
(a) Which two of the following compounds would you mix to make a buffer of pH 7.45: H3PO4 (FM 98.00), NaH2PO4 (FM 119.98), Na2HPO4 (FM 141.96), and Na3PO4 (FM 163.94)?(b) If you wanted to prepare
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