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We’ll show you how to calculate the pH of a solution formed by mixing a strong acid with a strong base.
Strong Acid– Strong Base
Mixtures
We’ll consider adding equal amounts of a strong acid and a strong base to the beaker on the bottom.
Strong Acid
Strong
Base
Strong acids contribute hydronium ions to aqueous solutions.
H3O+
Strong Acid
Strong
Base
Acids can more simply be viewed as donating protons or H+ ions. HERE, we’ll consider acids as a source of H+ ions.
H+
Strong Acid
Strong
Base
And bases are a source of hydroxide or OH minus ions.
H+
Strong Acid
Strong
Base
OH–
When a strong acid is added to a container (click), it brings H+ ions with it.
Strong Acid
Strong
Base
OH–H+
And when a strong base is added (click), it brings hydroxide or OH minus ions with it. Of course when the base is added it immediately mixes with the acid.
Strong Acid
Strong
Base
H+
OH–
However, here we’ll pretend it doesn’t mix yet, so we can get a more detailed idea of the processes.
OH–
Strong Acid
Strong
Base
H+
As the solutions mix, H+ and OH minus ions move toward each other.
OH–
Strong Acid
Strong
Base
H+
And in the process of neutralization, react with each other to form water.
OH–
Strong Acid
Strong
Base
H+
H2O
2H OOHH
And the spectator ions in the acid and base will be present as a neutral salt.
Strong Acid
Strong
Base
H2O and a Salt
Now we’ll use a slightly different model to visualize adding a strong acid to a strong base. In this case we’ll start with equal moles (click) of H+ and OH minus, and move these together.
Strong Acid
H+
H+
H+
H+
H+
H+
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
The H+ and OH- will neutralize each other to form water.
Strong Acid
H+
H+
H+
H+
H+
H+
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
H2OH2OH2OH2OH2OH2O
and there is no strong acid or base left over,
H2OH2OH2OH2OH2OH2O
so the final mixture is neutral
H2OH2OH2OH2OH2OH2O
The Final Mixture
is Neutral
This time the acid we’re starting with has more H+ than the base has OH minus. The H+ is in excess.(click)
Strong Acid
H+
H+
H+
H+
H+
H+
H+
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
Each OH- ion will neutralize an H+ ion to form water
Strong Acid
H+
H+
H+
H+
H+
H+
H+
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
H2OH2OH2OH2OH2OH2O
But since we had started with an excess of H+, we have some H+ left over. There weren’t enough OH minus ions available to neutralize all the H+ ions we added.
H+
H2OH2OH2OH2OH2OH2O
ExcessH+ Left Over
Because there is H+ left over, the final mixture is Acidic
H+
H2OH2OH2OH2OH2OH2O
The Final Mixture is Acidic
ExcessH+ Left Over
Now we’ll look at another combination.This time the base we’re starting with has More OH minus than the acid has H+. The OH minus is in excess (click). So we combine them.
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
Strong Acid
H+
H+
H+
H+
H+
Each H+ ion present will neutralize one OH- ion to form water.
Strong
Base
OH–
OH–
OH–
OH–
OH–
OH–
Strong Acid
H+
H+
H+
H+
H+
H2OH2OH2OH2OH2O
This time, we have excess OH minus left over.
OH–
H2OH2OH2OH2OH2O
Excess OH– Left
Over
so the final mixture is basic.
OH–
H2OH2OH2OH2OH2O
Excess OH– Left
Over
The Final Mixture is Basic
Now we’ll do an example question. We’re told that 18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH.
And we’re asked to find the pH of the final mixture.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
We’ll begin by finding the initial moles of H+ added.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol HCl 0.0180 L 0.00360 mol H
1m
Lol Hin ini itial ltia
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Because the source of H+, HCl is a strong monoprotic acid, the moles of H+ is equal to the moles of HCl.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H 0.0180 L 0.mol 00360 mol H
1L HClin ini itial tial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
The moles of HCl is equal to 0.200 moles per L
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 mmol H mol HCl 0.00360 mol
ol0.0180 L
1LHinitial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
times 0.0180 L
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.00360 mol H
10.0180
LLinitial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Which is 0.00360 moles. So 0.00360 moles of H+ was added.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 m0.00360 mol H
olmol H mol HCl 0.0180 L
1Linitial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Now we’ll calculate the initial moles of OH minus added.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 mol mol NaOH 0.0250 L 0.00400 mol OH
1H
Lmol O i inn iitial tial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Because NaOH is a strong base with one OH in its formula, the moles of OH minus is equal to the moles of NaOH added.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 mol mol OH 0.0250 L 0.0mo 0400 mol OH
1N
Ll aOHi inn iiti ta iall
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
the moles of NaOH is 0.160 moles per L
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 mmol OH mol NaOH 0.00400 mol OH
ol 0.0250 L
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
times 0.0250 L
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 mol mol OH mol NaOH 0.00.0250 0400 mol OH
1L
Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
which is 0.00400 moles. So the initial moles of OH minus added is 0.00400 mol.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 m0.00400 mol OH
ol mol OH mol NaOH 0.0250 L
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Notice that both the moles of H+ and OH minus are expressed to 3 significant figures, which is consistent with the given data
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00 mol H
1L360initial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00 mol OH
1L400 initial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Also notice that both of these values have 5 decimal places. Next we check whether moles of H+ or moles of OH minus is in excess
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0. mol H
10
L0360initial initial
0.160 m0
ol mol OH mol NaOH 0.0250 L 0. mol OH
1L0400 initial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.00400 moles is greater than 0.00360 moles, so OH minus is in excess.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 m0.00400 mol OH
ol mol OH mol NaOH 0.0250 L
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
OH– is in Excess
Now, 0.00360 moles of H+ will neutralize 0.0036 moles of OH minus.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 m0.00360 mol H
olmol H mol HCl 0.0180 L
1Linitial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Will neutralize 0.00360 mol OH–
So the excess moles of OH minus left over will be
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
0.00400 mol OH 0.00360excess m mol H 0.00040 mol Ol HOH o
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
Will neutralize 0.00360 mol OH–
The initial 0.00400 moles
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.160 m0.00400 mol OH
ol mol OH mol NaOH 0.0250 L
1Linitial initial
0.00400 mol Oexcess mol OH 0.00360 mol H 0.00040 mol OHH
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
minus the 0.00360 moles of H+ that was able to neutralize 0.00360 moles of OH minus.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 m0.00360 mol H
olmol H mol HCl 0.0180 L
1Linitial initial
excess mol OH 0.00400 mol O 0.00360 moH 0.00040 mol Hl H O
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
Which is equal to 0.00040 moles. And because OH minus is the ion in excess, this is 0.00040 moles of OH minus.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mo 0.00040 mol OHl H
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
Because the numbers that were subtracted to get this both have 5 decimal places, the value 0.00040 must also have 5 decimal places.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
excess mol OH mol O0.00400 0.00360H mol H mol 0.00 OH040
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
5 decimal places
5 decimal places
5 decimal places
But notice this value, expressed to 5 decimal places, has only 2 significant figures. Zero’s to the left of the first non-zero digit are not significant. So our final answer cannot have more than 2 significant figures.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.000 mol OH40
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
2 significant figures
Because OH minus is the ion in excess, we now calculate the concentration of OH minus in the final mixture.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
0.00040 mol OH 0.00040 mol OH
0.0093 M0.0430 L0.0180 L 0.
Final O0250 L
H
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
Concentration of OH minus is moles of OH minus over the total volume in Litres. We have 0.00040 moles of OH minus
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mo 0.00040 mol OHl H
0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.
0.00040 m
0250
ol OH
L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
And the total volume of the mixture is 0.0180 L of the HCl solution
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.00360 mol H
10.0180
LLinitial initial
0.0180 L 0.0250
0.00040 mol OH 0.00040 mol OHFinal OH 0.0093 M
0.0430 LL
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
plus 0.0250 L of NaOH solution.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.0180 L 0.0250
0.00040 mol OH 0.00040 mol OHFinal OH 0.0093 M
0.0430 LL
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.00.0250 0400 mol OH
1L
Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Or 0.0430 L. So the final concentration of OH minus is 0.00040 moles divided by 0.0430 L,
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH
Final OH 0.0093 M0.0180 L 0.
0.00040 mol OH
0.0430 L0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Which is 0.0093 M.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH0.0430 L0.0180 L 0.
0.0093 M0250 L
pOH log OH log 0.0093 2.03 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
We want to find the pH of the mixture, but since we have the OH minus concentration, we start by calculating the pOH, which is the negative log of the hydroxide ion concentration
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
log 0.0093 2.pOH log H 03O pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Or the negative log of 0.0093
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH M0.0430 L0.0180 L 0.0
0.0025 L
90
3
log 0.00pOH log OH 2.093 3 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Which is 2.03. Take a moment to check this on your calculator. Remember, 2 decimal places in a pOH value is 2 significant figures.
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.00 2.0393 pH 14.00 pOH 14.00 2.03 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
In the last step, we’ll calculate the pH
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 14.0pH 14 0 2.03 11.0 70 p 9OH .
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Which is 14 minus the pOH
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 pH 14.0014.00 2.03 11.97pOH
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Or 14 minus the 2.03
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.00 2.0393 14.0pH 14.00 pOH 11.0 92.03 7
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
Which is 11.97.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 14.00 pOH 14.00 2.03pH 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
pH of the final mixture
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.
So we’ve now answered what we set out to answer. The pH of the final mixture is 11.97. This is expressed to 2 decimal places, which in a pH value, is 2 significant figures.
0.200 molmol H mol HCl 0.0180 L 0.00360 mol H
1Linitial initial
0.00040 mol OH 0.00040 mol OH
Final OH 0.0093 M0.0430 L0.0180 L 0.0250 L
pOH log OH log 0.0093 2.03 14.00 pOH 14.00 2.03pH 11.97
0.160 mol mol OH mol NaOH 0.0250 L 0.00400 mol OH
1Linitial initial
excess mol OH 0.00400 mol OH 0.00360 mol H 0.00040 mol OH
pH of the final mixture
18.0 mL of 0.200 M HCl is added to 25.0 mL of 0.160 M NaOH. Find the pH of the final mixture.