Here we’ll go over an example in which a strong acid is mixed with a strong base, and we calculate the pH of the final mixture. Strong Acid–Strong Base Mixture Calculations Example 2

We’re given that mL of M H 2 SO 4 is mixed with mL of M KOH mL of M H 2 SO 4 is mixed with mL of M KOH.

And we’re asked to determine the pH of the final mixture mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Just a few words about sulphuric acid, H2SO mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

H2SO mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H 2 SO 4

is a Diprotic Acid mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H 2 SO 4 is a Diprotic Acid

Which means it has 2 protons it can lose mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H 2 SO 4 is a Diprotic Acid It has 2 protons it can lose.

As soon as H 2 SO 4 is added to water, it ionizes completely to lose its first proton: mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? When H 2 SO 4 is added to water, it ionizes completely to lose its first proton:

100% of the H2SO4 molecules lose one proton (click) to form hydronium and hydrogen sulphate ions mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? When H 2 SO 4 is added to water, it ionizes completely to lose its first proton: H+H+

But when its just in water, the second proton does not come off as easily. This proton comes off when HSO4 minus ionizes. But HSO4- is a weak acid so its ionization in water is very limited mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? When H 2 SO 4 is added to water, it ionizes completely to lose its first proton: But its second proton does not come off as easily in water: Equilibrium Weak Acid

However, when H 2 SO 4 is mixed with the STRONG BASE KOH, this is a totally different situation mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? When H 2 SO 4 is mixed with the strong base KOH, this is a totally different situation.

When an H2SO4 molecule enters water, it loses one proton (click) to water, to form a hydronium ion (H3O+) and a hydrogen sulphate ion (HSO4 minus) mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H+H+

Models of these are shown here. Take a moment to check the atoms and the charges and see how the formulas relate to the structural models mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? O H H H + O O H S O O – H+H+

When the strong base KOH dissociates in water it forms K+ and OH minus ions. Here we doubled everything in the equation mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2KOH  2K + + 2OH – O H H H + O O H S O O –

we show models of the two hydroxide ions from the KOH mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? O H H O – – 2KOH  2K + + 2OH – O H H H + O O H S O O –

One of the hydroxide ions collides with the hydronium ion mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H O O H – – O H H H + O O H S O O –

and takes away a proton, to form 2 water molecules mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H O – O H H H O H O O H S O O –

The other hydroxide ion collides with the hydrogen sulphate ion (click) mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H O H O H – O H H O O H S O O –

And takes a proton from it to form a water molecule and a suphate ion mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? O O S O O – H O H H O H – O H H

the sulphate ion has the formula SO4 2 minus mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? H O H H O H O O S O O – – Sulphate SO 4 2– O H H

So, in an indirect way, 2 hydroxide ions are able to remove both protons from a molecule of H2SO4. We‘ll show this with equations mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Two OH – ions were able to remove both protons from H 2 SO 4.

As soon as H2SO4 is added to water it ionizes completely to form a hydronium ion and a hydrogen sulphate ion. We’ll call this Step mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Two OH – ions were able to remove both protons from H 2 SO 4. Step 1

When we add a strong base, one OH minus ion neutralizes the hydronium ion to form 2 water molecules. We’ll call this step mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Two OH – ions were able to remove both protons from H 2 SO 4. + Step 2

And the other OH minus ion reacts with hydrogen sulphate to form water and a sulphate ion. We’ll call this Step mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Two OH – ions were able to remove both protons from H 2 SO Step 3

Even though we know these 3 steps occur when we add H2SO4 to water and then add a strong base, mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Even though we know that these steps occur… 1 2 3

We can represent the process with a net overall equation: H2SO4 plus 2 OH minus form 2H2O plus SO4 2minus mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? Even though we know that these steps occur… We can represent the process with a net overall equation

so in the overall net reaction, we see that each H2SO4 (click) donates 2 protons or H+ ions to the hydroxide ions mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2 H + Each H 2 SO 4 donates 2 protons to the OH– ions

From this, we can write the conversion factor stating there are 2 moles of H+ per 1 mole of H2SO4. We can use this conversion factor in any calculation where H2SO4 reacts with a strong base mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2 H + Each H 2 SO 4 donates 2 protons to the OH– ions

Now we’ll do the calculations for this problem. We’ll begin by calculating the initial moles of H+ added mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Its equal to moles of H2SO4 per Litre… mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Times 2 moles of H+ to 1 mole of H2SO4… mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Times L mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Which comes to moles of H+. Notice moles of H2SO4 and Litres cancel out mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

In order to preserve 3 significant figures (the lowest number of significant figures in the given data)… mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 3 significant figures

The answer to this must be expressed to 4 decimal places mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 4 decimal places

Now we’ll calculate the initial moles of OH minus added mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

It is equal to moles of KOH per L mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Times 1 mole of OH minus to 1 mole of KOH mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Times L mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Which comes out to moles of OH minus. You can see that moles of KOH and Litres both cancel. Notice we also have 3 significant figures and 4 decimal places in this answer mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Now we compare the initial moles of H+ and OH minus. We see that , the moles of H+, is greater than , the moles of OH minus mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

So the H+ is in excess and the OH minus is the limiting reagent mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? In Excess Limiting Reagent

We calculate the excess moles of H+… mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

By taking moles of H mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

and subtracting moles of OH minus mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

To give us moles of H+ in excess mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

This answer, , has 4 decimal places, because the numbers we subtracted both had 4 decimal places mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 4 decimal places

But we can see that written this way, this number has only 2 significant figures, the 7 and the 5. Therefore the final answer to this problem cannot have more than 2 significant figures mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2 significant figures

The next step on the way to pH, is to find the hydronium ion concentration mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Which is equal to the concentration of H+. These are synonymous in chemistry dealing with aqueous solutions mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

The concentration of H+ is equal to moles of H+ per Litre of solution. The moles of H+ is moles mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

And the total volume of the mixture is L of H2SO4 … mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Plus L of KOH mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

So the concentration of H+ or H3O+ is moles over L mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Which comes out to molar. We’ll carry one more significant figure than the 2 our final answer is limited to. We’ll round to 2 significant figures at the end mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

In the last step, we’ll find the pH of the mixture mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Remember, pH is defined as the negative log of the hydronium ion concentration mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

Which is the negative log of mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture?

, which comes out to mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2 significant figures

In a pH, the digits to the right of the decimal are significant. So this answer has 2 significant figures mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? 2 significant figures

Now we have answered the original question. The pH of the final mixture is This low value means the solution is fairly acidic. This is reasonable because a strong acid is in excess in this case mL of M H 2 SO 4 is mixed with mL of M KOH. What is the pH of the final mixture? pH of Final Mixture