Can someone help me over here? I need an negative charge and also another thing is that in a question it asked me to use somethi
ng that would represent an ion. I’m not sure on what to choose either Hydrogen or Helium but just please send help. Please just please help me I NEED URGENT HELP :(
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Here is the full question
Find the pH during the titration of 20.00 mL of 0.1000 M butanoic acid, CH3CH2CH2COOH (K a = 1.54 × 10 − 5), with 0.1000 M NaOH solution after the following additions of titrant (total volume of added base given):
a) 10.00 mL
pH = <u> </u>
b) 20.10 mL
pH = <u> </u>
c) 25.00 mL
pH = <u> </u>
<u />
Answer:
pH = 4.81
pH = 10.40
pH = 12.04
Explanation:
a)
Number of moles of butanoic acid
=
= 0.002000 mol
Number of moles of NaOH added
=
= 0.001000 mol
pKa of butanoic acid = - log Ka
= - log ( 1.54 × 10⁻⁵)
= 4.81
Equation for the reaction is expressed as follows:
CH₃CH₂CH₂COOH + OH⁻ -----> CH₃CH₂COO⁻ + H₂O
The ICE Table is expressed as follows:
CH₃CH₂CH₂COOH + OH⁻ -----> CH₃CH₂COO⁻ + H₂O
Initial 0.002000 0.001000 0
Change - 0.001000 - 0.001000 + 0.001000
Equilibrium 0.001000 0 0.001000
Total Volume = (20.00 + 10.00 ) mL
= 30.00 mL = 0.03000 L
Concentration of [CH₃CH₂CH₂COOH] =
= 0.03333 M
Concentration of [CH₃CH₂COO⁻] =
= 0.03333 M
By Henderson- Hasselbalch equation
pH = pKa + log
pH = pKa + log
PH = 4.81 + log
pH = 4.81
Thus; the pH of the resulted buffer solution after 10.00 mL of NaOH was added = 4.81
b )
After the equivalence point, we all know that the pH of the solution will now definitely be determined by the excess H⁺
Number of moles of butanoic acid
=
= 0.002000 mol
Number of moles of NaOH added
=
= 0.002010 mol
Following the previous equation of reaction , The ICE Table for this process is as follows:
CH₃CH₂CH₂COOH + OH⁻ -----> CH₃CH₂COO⁻ + H₂O
Initial 0.002000 0.002010 0
Change - 0.002000 -0.002000 + 0.002000
Equilibrium 0 0.000010 0.002000
We can see here that the base is present in excess;
NOW, number of moles of base present in excess
= ( 0.002010 - 0.002000) mol
= 0.000010 mol
Total Volume = (20.00 + 20.10 ) mL
= 40.10 mL ×
= 0.04010 L
Concentration of acid [OH⁻] =
=
Using the ionic product of water:
where
=
pH = - log
pH = - log []
pH = 10.40
Thus, the pH of the solution after the equivalence point = 10.40
c)
After the equivalence point, pH of the solution is determined by the excess H⁺.
Number of moles of butanoic acid
=
= 0.002000 mol
Number of moles of NaOH added
=
= 0.002500 mol
From our chemical equation; The ICE Table can be illustrated as follows:
CH₃CH₂CH₂COOH + OH⁻ -----> CH₃CH₂COO⁻ + H₂O
Initial 0.002000 0.002500 0
Change - 0.002000 -0.002000 +0.002000
Equilibrium 0 0.000500 0.002000
Base is present in excess
Number of moles of base present in excess = [ 0.002500 - 0.002000] mol
= 0.000500 mol
Total Volume = ( 20.00 + 25.00 ) mL
= 45.00 mL
= 45.00 ×
= 0.04500 L
Concentration of acid [OH⁻] =
= 0.01111 M
Using the ionic product of water
=
= M
pH = - log
pH = - log []
pH = 12.04
Thus, the pH of the solution after the equivalence point = 12.04