Buffers and titration

Question 1

What are buffers? An why are they important

Answer 1

1. Acid and base reactions that allows for the product to form a slat and neutralize a solution so that the pH is stable.

Human Application

1. The human body is very much dependent on these reactions in order to stay healthy. Blood cannot have a pH different than 7.4 or else we can die.
2. The kidney and lungs play a huge part in creating acidicy.

Question 2

What are the four types of buffers?

Answer 2

1. Weak acid + and the salt of the conjugate base
   
   1. Once the salt ionizes in the solution, it allows the solution to have both acids and bases which neutralize any added acid and base to the solution.
2. weak base and the salt of it’s conjugate acid ( same as above)
3. 1 mole of a weak acid + 0.5 mole of a strong base
   
   1. because the strong base is so strong you only need a little bit to neutralize the solution
4. 1 mole of a weak base + 0.5 mole of a strong acid.
   
   1. Because the strong acid is so strong you need only a little bit to neutralize the solution.

Best equivalent when the concentration of the acid = the conjugate base

• pKa gives you the pH at which you will have 50% of the acid and 50 % of the base.

Question 3

What are titrations?

Answer 3

1. It is an experiment done in a lab that allows us to determine how much of an acid or a base that we have in a solution.

Titration graphs:

1. On the y-axis: pH values
2. On the x-axis the volume of the known acid or base that you have

Question 4

How do titrations work for strong acid and strong base?

Answer 4

So say you have an unknown strong acid mix into a solution how can you determine how much of the acid is in that solution

Titration

1. You can titrate the acid with a strong base in order to obtain the M ration of the acid within the solution
2. What to do: add the base in a controlled manner keeping up with the volume added to the solution.
3. Indicator: you can add an indicator to the beaker that will let us known when the strong base is equivalent to the moles of the strong acid.
   
   1. changes color at 50% of acid = 50 % of base

Question 5

What can the equivalent of a buffer tell us?

Answer 5

1. Strong base + Strong acid ( or vice versa)
   
   1. equivalent pt will be 7
2. Weak base + strong acid
   
   1. equivalent pt will be < 7 because the strong acid will eventually win
3. Weak acid + strong base
   
   1. the equivalent pit will be > 7 because the strong base will eventually win.

Equivalent pt formula that can give us an insight into the mole of the unknown

M1 V1 =M2 V2 ( use that formula to calculate what you want)

Question 6

what is special about weak acids and weak base titration curve?

Answer 6

1. Because they can ionized they will express a pka that will usually be 1/2 in volume on the titration curve, before reaching the equivalent point.
2. Because they are ionizable you can also make use of an ice table in order to calculate their concentration.

Question 7

What are the two polyproptic acids?

Answer 7

1. H3PO4 pka values
   
   1. first H leaves at 2
      
      1. Equivalent pt: 1/3 ( give us the first value of the base to match the first acid)
   2. second H leaves at 7
      
      1. equivalent pt: 2/3
   3. third H leaves at 12
      
      1. equivalent pt 3/3
2. H2CO3. ( carbonic acid)
   
   1. pka at 3.6
   2. pKa 6.3