Buffers

Question 1

Buffer

Answer 1

a solution that is resistant to pH change

Question 2

A buffer needs

Answer 2

need a weak acid + its conjugate base
or
need a weak base + its conjugate acid

Question 3

how to make a buffer

Answer 3

reacting a strong acid with a weak base or reacting a strong base with a weak acid
AS LONG AS THE STRONG SPECIES IS THE LIMITING REACTANT

Question 4

calculating the pH of a Buffer

Answer 4

1. taking dilution into account
   - multiply the concentration of the compound by (the amount added in mL/the total volume in mL)
2. Either use the ICE box or the H/H equation
   WHEN USING AN ICE BOX THE COMPOUNDS ARE NOT 0 THEY ARE EQUAL TO THEIR DILUTION

Question 5

H/H equation

Answer 5

pH = pKa + log [A-]/[HA-]

Question 6

Selecting the most appropriate weak acid and conjugate base for making a buffer at a specific pH

Answer 6

the most appropriate weak acid is the one that has its pKa closest to pH of the buffer

Question 7

calculating the correct amounts of weak acid and weak base in order to make a buffer at a certain pH

Answer 7

1. letting one of the compounds be x and another to be the amount of buffer needed subtracted by x
2. take dilution into account
3. using the H/H equation and plugging the dilution values in
4. taking the inverse of log of the other side
5. solve for x and then plug back into the values that were assigned

Question 8

Calculating pH of a buffer after addition of a strong acid

Answer 8

1. take diluation into account
2. calculate the pH using H/H equation using the dilution values into account
3. For the original compounds multiply the dilution concentration by the total original volume
4. for the added H+ multiply the concentration by the volume added
5. Use ICFF table for the initial concentration use the values calculated in step 4. Subtract by the added H+. For the F(M) use the subtracted value and divide by TOTAL volume of the whole thing
6. use the H/H equation

Question 9

Calculating the pH of a buffer after the addition of a strong base

Answer 9

1. take diluation into account
2. calculate the pH using H/H equation using the dilution values into account
3. For the original compounds multiply the dilution concentration by the total original volume
4. for the added OH- multiply the concentration by the volume added
5. Use ICFF table for the initial concentration use the values calculated in step 4. Subtract by the added OH-. For the F(M) use the subtracted value and divide by TOTAL volume of the whole thing
6. use the H/H equation

Question 10

Ka

Answer 10

the [H+] in the buffer

Question 11

Finding the solution that will ionize a solution less than it does in pure water

Answer 11

its conjugate acid or base

Question 12

Solving an equilibrium problem (using an ICE table) to calculation the pH of each solution

Answer 12

1. Write the equation (the acid or base first + water) if acid it produces H3O; if base OH- is produced
2. place x and solve for it using Ka
3. negative log of Ka to find pH

Question 13

Calculate the percent ionization

Answer 13

[H3O+]/[inital molarity] x 100%

Question 14

calculate the ratio of a solution to create a buffer at a certain pH

Answer 14

plug in pH into H/H equation and pKa then take the inverse log

Question 15

finding the initial pH of a buffer solution

Answer 15

plug into H/H equation

Question 16

the pH after the addition of certain mg

Answer 16

• (total volume in L)(the molarity) (DO IT FOR EACH COMPOUNDS)
• convert mg to g to mol of each compound
• plug into ICE box but each component is in mol
• subtract to add by the number found by converting mg to g to mol
• divide the original compounds by the amount in L
• plug into H/H formula