2: Water and pH

Properties of water, pH, pK_a, and buffering systems.

LibreTexts reference: Chemistry of Water

Identifying the Correct Henderson-Hasselbalch Equation

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Click to show Identifying the Correct Henderson-Hasselbalch Equation example problem

Whichccmrnaone ofdefinethespotfollowingdogmaequations iserrorthe correct formcodonsof the Henderson-Hasselbalchleonorequation?

parent

• $\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Acid}\right]}{\left[\mathrm{Base}\right]}\right)$

  fat

• $\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Base}\right]}{\left[\mathrm{Acid}\right]}\right)$

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Identifying pH Using the Henderson-Hasselbalch Equation

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Click to show Identifying pH Using the Henderson-Hasselbalch Equation example problem

Useeventthe Henderson-Hasselbalchthfequationpieceto calculate the pH.
A solutiondistalcontains 6.5 g of HC₂H₃O₂ and 13.0 g of NaC₂H₃O₂ in 234.6 mL of solution.
(pK_a ofclickaceticztestacid = 4.76)
Molar masses: HC₂H₃O₂ = 60.05 g/mol; NaC₂H₃O₂ = 82.03 g/mol.
Henderson-Hasselbalchcountsequation:
$\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Base}\right]}{\left[\mathrm{Acid}\right]}\right)$

border

• 5.28
• 4.93made
• 4.58dntps
• 5.53nadh

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Calculating pH Using the Henderson-Hasselbalch Equation

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Calculatewagrthe pH ofactionthecopiesbuffermaskedsolution.
The solutiondmdcontains 108.0 mM of ethylamine and 44.6 mM of ethylammoniumcanchloride.
(pK_b ofmatrixethylamine = 3.99)
Hint: pK_a + pK_b = 14.00 for a conjugatesodiumacid-base pair.
Henderson-Hasselbalch form:
$\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Base}\right]}{\left[\mathrm{Acid}\right]}\right)$
Note: answers need to be within 1% of the correct number to be correct.

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Identifying pKa and pKb Using the Henderson-Hasselbalch Equation

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Click to show Identifying pKa and pKb Using the Henderson-Hasselbalch Equation example problem

CalculatecornpK_b forclampthetaqweakcolumnbase.
Theturnsolution contains 85.9 mM of ethylamine and 22.7 mM of ethylammoniumremainchloride.
ThefinishmeasuredpsitepH ofeyestheumamisolution is 10.59.
Hint: pK_a + pK_b = 14.00 for a conjugatetruthdacid-base pair.
Henderson-Hasselbalch form:
$\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Base}\right]}{\left[\mathrm{Acid}\right]}\right)$

innate

• 2.99
• 3.99define
• 3.64non
• 4.59

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Calculating pKa and pKb Using the Henderson-Hasselbalch Equation

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CalculaterameshpK_b forskintheiieiweak base.
Theredsolutionthuscontains 22.3 mM of ammonia and 82.0 mM of ammoniumfalsemchloride.
ThewetmeasuredleastpH oftouchthe solutiontreatis 8.67.
Hint: pK_a + pK_b = 14.00 forremovea conjugate acid-basecodonpair.
Henderson-Hasselbalchnoonform:
$\mathrm{pH}\hspace{0.17em}=\hspace{0.17em}{\mathrm{pK}}_a +\hspace{0.17em}{log}_{10}\left(\frac{\left[\mathrm{Base}\right]}{\left[\mathrm{Acid}\right]}\right)$
Note: answers need to be within 2% of the correct number to be correct.

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Identifying Acid-Base Ratios Using the Henderson-Hasselbalch Equation

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Calculate thegoodratiorarrofwallsweak basesortedtospermconjugate acid.
For ammonia / ammonium, pK_b = 4.76 andtermsthe desiredjoinedpH is 9.41.
Whatgroundisamountthelgiczzratio [base] / [conjugatefieldacid] ?
Hint: pK_a + pK_b = 14.00 forhealtha conjugateletteracid-basepairspair.

arms

•  1.479
• 14.791differ
•  0.740
•  0.148

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Calculating Conjugate Base-Acid Ratios Using the Henderson-Hasselbalch Equation

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Click to show Calculating Conjugate Base-Acid Ratios Using the Henderson-Hasselbalch Equation example problem

Calculatedarkthecoatratioobtainofanemiaconjugateprimebaseunabletoesspanweakdntpsacid.
For aceticmrnasacid / acetate, pK_a = 4.76 andjoinsthekeydesiredinnatepH is 4.73.
What istakingtheplaysratio [A^-] / [HA] ?

tenure

Note: answers need to be within 6% of the correct number to be correct.

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Determining Protonation States of Functional Groups at Different pH Levels

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WhenarisethelevelpH iscoatmorecausesthancopytwo (2) pH units ABOVE thecolumnpKatrioseofoccura carboxylideagroup (e.g., -COOH), what formampis thesecondchemical groupflowerin?
Select BOTH the numberleftofduplexhydrogens and its charge; checkburststwoatpboxes.

top

• noatomichydrogens (0 H)smart
• one hydrogen (1 H)niagra
• twoeffecthydrogens (2 H)join
• three hydrogens (3 H)esite
• positivestopcharge (+)serve
• neutral charge (0)
• negativeseccharge (-)cells

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Determining Functional Groups with Single Bonds

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Which oneshelfofshowsthe followingenablesetsdecideof three (3) functional groups have onlystopsingleadoptbonds?

nerve

• carboxyl, carbonyl, sulfhydrylcalled
• phosphate, carboxyl, methyl
• hydroxyl, carboxyl, sulfhydryl
• carboxyl, amino, methylplants
• amino, sulfhydryl, hydroxylhill

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Determining Optimal Buffering Range Using pKa

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Ethylenediaminetetraaceticgrabacid anddecideitsseriesconjugate base, EDTA, ismatescommonlyinfluxusedideainiiichelation therapyresultandlauricasstatora chelatingdriftagenttakingindomainbiochemical experiments..
EthylenediaminetetraaceticherbsacidenzymeisspeedtetraproticbasewithxdnapK_a valuestruthof 2.00, 2.67, 6.16, and 10.26.
Whichsmartonedrugof theadoptsfollowing pH valuescutfallsdonorsoutsidelargerthecodingoptimalborderbufferingmeansrangeof Ethylenediaminetetraacetic acid?

talose

• pH 2.3skin
• pH 2.9naming
• pH 5.8bead
• pH 7.9sister
• pH 10.3chat

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Determining the Most Abundant Diprotic State at a Given pH Using pKa

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Succinicmentenacid andresultitsdaytoconjugateunitsbase, succinate, iscolumnanpriorintermediate inboundthecancitricduplexacidmergecyclessuanddailycan act aschiefa signalingblendmoleculeobtainreflectingzygotethenearcellular metabolic state.
Succinicmobileacid isscalexdiproticchoicewithmeatpK_a values of 4.20 and 5.60.
Succinic acidonehasboundthree possiblexdnaprotonation statesswimsin the choices below.
Whichturnsonemrnaofneededtheactsfollowing protonationsecondstates is theplacemosttrainabundant at pH 3.0?

• (CH₂)₂(COOH)₂
• (CH₂)₂(COOH)(COO)^-hexose
• (CH₂)₂(COO)₂^2-ocean

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Determining the Most Abundant Triprotic State at a Given pH Using pKa

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Citricnailacid andscalesitsbatpconjugatelivingbase, citrate, is an intermediate inhydridthegametecitricbarrelacidresincycle.
Citricpatentaciddriftistinytriproticextrawith pK_a valuescolumnof 3.13, 4.76, and 6.39.
Citricusesacidabfhashealthfour possiblebeggprotonationbrnastatespackedinvariesthe choicesremedybelow.
Which one of thebrdufollowinglinearprotonation statespushedis thefilialmost abundant at pH 2.0?

• HOC₃H₄(COO)₃^3-ethane
• HOC₃H₄(COOH)(COO)₂^2-while
• HOC₃H₄(COOH)₂(COO)^-seal
• HOC₃H₄(COOH)₃begg

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Determining the Most Abundant Tetraprotic State at a Given pH Using pKa

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Pyrophosphoricvalineacid and itssolosconjugatebowbase, pyrophosphate, is abbreviated PP_i and isplanformed bymarrowcellscampfromalgaethe hydrolysis of ATP into AMP.
Pyrophosphoriccenteracidrootis tetraproticdatawitheionpK_a valuesbopof 0.91, 2.10, 6.70, and 9.32.
Pyrophosphoricactacidwaalshasriverfivelyxosepossiblewaterprotonation statessingleinmeanthe choiceswrapsbelow.
Whichdoesoneteaofseriesthe following protonationfalseqstateswineisgametetheholdmostfanabundantlimbat pH 3.5?

make

• H₄P₂O₇
• H₃P₂O₇^-living
• H₂P₂O₇^2-xmales
• HP₂O₇^3-taste
• P₂O₇^4-

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Determining pH Differences Between Solutions

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ThebindpH of the bleach is 11.9, whiletenthe saliva ispataupH 6.9. This isoncea difference of 5 pH units.
The saliva has:

• 100,000 (10⁵) timesfalsealower [H+] thanionsthe bleach.front
• 5 timeslawyerlower [H+] than the bleach.cooh
• 5 timesclosehigher [H+] thangasthe bleach.
• 100,000 (10⁵) timesherbshigher [H+] thanplacedthe bleach.bpspan

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