Assignment 8: 15.1 - 15.8

25 July 2022
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question
HCl Express your answer as a chemical formula.
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Cl−
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H3PO4 Express your answer as a chemical formula.
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H2PO4−
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HCHO2 Express your answer as a chemical formula.
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CHO2−
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HF Express your answer as a chemical formula.
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F−
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C2H5NH2 Express your answer as a chemical formula.
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C2H5NH3+
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ClO4− Express your answer as a chemical formula.
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HClO4
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HPO42− Express your answer as a chemical formula.
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H2PO4−
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HCO3− Express your answer as a chemical formula.
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H2CO3
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Classify each of the following acids as strong or weak. HF
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Weak
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HCHO2
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weak
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H2SO4
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strong
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H2CO3
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weak
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Write an expression for the acid ionization constant (Ka) for HCHO2.
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Ka=[H3O+][CHO2−]/[HCHO2]
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Write an expression for the acid ionization constant (Ka) for HF.
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Ka=[H3O+][F−]/[HF]
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Write an expression for the acid ionization constant (Ka) for H2CO3.
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Ka=[H3O+][HCO−3]/[H2CO3]
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Consider the given acid ionization constants. Identify the strongest conjugate base. Acid Ka HNO2(aq) 4.6×10−4 HCHO2(aq) 1.8×10−4 HClO(aq) 2.9×10−8 HCN(aq) 4.9×10−10
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CN−(aq)
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What is the pH of a solution whose hydroxide ion concentration, [OH-], is 4.3 × 10-4 M?
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10.63
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What is the H+ concentration for an aqueous solution with pOH = 3.58 at 25 ∘C? Express your answer to two significant figures and include the appropriate units.
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[H+] = 3.8×10−11 M
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Arrange the following aqueous solutions, all at 25 ∘C, in order of decreasing acidity. Rank from most acidic to most basic. To rank items as equivalent, overlap them.
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Most acidic to least: 0.0023M HCl pH= 5.45 & pOH= 8.55 0.0018 M KOH
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At a certain temperature, the pH of a neutral solution is 7.24. What is the value of Kw at that temperature? Express your answer numerically using two significant figures.
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Kw = 3.3×10−15
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What volume of a concentrated HCl solution, which is 36.0% HCl by mass and has a density of 1.179 g/mL, should be used to make 5.30 L of an HCl solution with a pH of 1.8? Express your answer with the appropriate units.
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V = 7.22 mL
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A certain weak acid, HA, has a Ka value of 9.7×10−7. Calculate the percent dissociation of HA in a 0.10 M solution. Express your answer as a percent using two significant figures.
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0.31 %
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Calculate the percent dissociation of HA in a 0.010 M solution. Express your answer as a percent using two significant figures.
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0.98%
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Find the pH of a 0.390 M aqueous benzoic acid solution. For benzoic acid, Ka=6.5⋅10−5. Express your answer using two decimal places.
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pH= 2.30
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Determine the pH of a solution that is 3.55% KOH by mass. Assume that the solution has density of 1.01 g/mL. Express your answer using two decimal places.
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pH= 13.81
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Aspirin (acetylsalicylic acid, C9H8O4) is a weak monoprotic acid. To determine its acid-dissociation constant, a student dissolved 2.00 g of aspirin in 0.600 L of water and measured the pH. What was the Ka value calculated by the student if the pH of the solution was 2.60? Express your answer numerically using two significant figures.
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Ka = 3.9×10−4
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A 0.100 M solution of ethylamine (C2H5NH2) has a pH of 11.87. Calculate the Kb for ethylamine. Express your answer numerically using two significant figures.
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Kb = 5.9×10−4
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If Kb for NX3 is 3.0×10−6, what is the pOH of a 0.175 M aqueous solution of NX3? Express your answer numericall
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pOH= 3.14
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If Kb for NX3 is 3.0×10−6, what is the percent ionization of a 0.325 M aqueous solution of NX3? Express your answer numerically to three significant figures.
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percent ionization = 0.304 %
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If Kb for NX3 is 3.0×10−6 , what is the the pKa for the following reaction? HNX3+(aq)+H2O(l)⇌NX3(aq)+H3O+(aq) Express your answer numerically to two decimal places.
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pKa= 8.48
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What is the relationship between the acid ionization constant for a weak acid (Ka) and the base ionization constant for its conjugate base (Kb )?
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Ka⋅Kb=Kw
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Which of the following anions act as weak bases in solution? Check all that apply.
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NO2− C2H3O2−
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For NO2−, write an equation that shows how the anion acts as a base. Express your answer as a chemical equation. Identify all of the phases in your answer.
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NO2−(aq)+H2O(l)⇌HNO2(aq)+OH−(aq)
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For C2H3O2−, write an equation that shows how the anion acts as a base. Express your answer as a chemical equation. Identify all of the phases in your answer.
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C2H3O2−(aq)+H2O(l)⇌HC2H3O2(aq)+OH−(aq)
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Determine the [OH−] of a solution that is 0.140 M in F−. Express your answer using two significant figures.
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[OH−] = 2.0×10−6 M
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Determine the pH of this solution. Express your answer to two decimal places.
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pH= 8.30
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Determine whether each of the following cations is acidic or pH-neutral. Sr2+
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pH- neutral
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Mn3+
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acidic
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C5H5NH+
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acidic
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Li+
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pH-neutral
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For Mn3+, write an equation that shows how the cation acts as an acid. Express your answer as a chemical equation. Identify all of the phases in your answer.
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Mn(H2O)63+(aq)+H2O(l)⇌Mn(H2O)5OH2+(aq)+H3O+(aq)
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For C5H5NH+, write an equation that shows how the cation acts as an acid. Express your answer as a chemical equation. Identify all of the phases in your answer.
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C5H5NH+(aq)+H2O(l)⇌C5H5N(aq)+H3O+(aq)
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Which aqueous solution is expected to have a pH less than 7?
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NH4Br (aq)
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Given that at 25.0 ∘C Ka for HCN is 4.9×10−10 and Kb for NH3 is 1.8×10−5, calculate Kb for CN− and Ka for NH4+. Enter the Kb value for CN− followed by the Ka value for NH4+, separated by a comma, using two significant figures.
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2.0×10−5,5.6×10−10
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Keep these values in mind for the remaining questions: Kb for CN− is 2.0×10−5. Ka for NH4+ is 5.6×10−10. Identify the following salts as neutral, acidic, or basic.
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Neutral Salts: SrBr2, LiNO3 Acidic Salts: NH4Br, NH4ClO4 Basic Salts: NH4CN, LiF, KCN
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Calculate the pH of a 0.20 M solution of KCN at 25.0 ∘C. Express the pH numerically using two decimal places.
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pH= 11.30
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Calculate the pH of a 0.20 M solution of NH4Br at 25.0 ∘C. Express the pH numerically using two decimal places.
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pH= 4.98