A buffer is a solution that resists large changes in pH when small amounts of acid or base are added.
A buffer acts like a chemical shock absorber for pH.
Showing a random 20 of 50 problems.
Example 1
medium
Why does diluting a buffer with water barely change its pH?
Example 2
medium
Make a buffer at pH 5.04 using pKa=4.74. What ratio [A−]/[HA] is required?
Example 3
challenge
How many moles of NaA must be added to 1.0 L of 0.20 M HA (pKa=4.70) to reach pH 5.00? (Assume volume constant.)
Example 4
easy
Does a buffer work equally well at any pH?
Example 5
medium
A buffer is 0.30 M NH3 and 0.30 M NH4+. Given pKa(NH4+)=9.25, find pH.Equal NH₃ and NH₄⁺ concentrations give pH = pKa
Example 6
easy
Is a solution of pure HCl a buffer?
Example 7
hard
Adding 0.10 mol HCl to 1.0 L pure water (initial pH 7) drops pH to about 1.0. The same 0.10 mol HCl in a 1.0 L buffer (0.50 M HA / 0.50 M A−, pKa=4.74) gives what new pH?
Example 8
medium
Use Henderson-Hasselbalch to find pH of a buffer with [A−]=[HA] and pKa=4.76.When [A⁻] = [HA], pH equals pKa
Example 9
easy
In a buffer, what neutralizes added base (OH−)?
Example 10
medium
A formic-acid buffer has pKa=3.75, [A−]=[HA]=0.20 M. Find pH.
Example 11
medium
After adding 0.01 mol OH- to a buffer with 0.10 mol HA and 0.10 mol A-, find the new mole ratio A−/HA.
Example 12
challenge
Compare buffer capacity of (a) 0.50 M HA / 0.50 M A- and (b) 0.05 M HA / 0.05 M A-, same pKa. Which resists pH change more and why?
Example 13
easy
Use Henderson-Hasselbalch: [A−]=0.10 M, [HA]=0.10 M, pKa=3.50. Find pH.
Example 14
easy
Which pair forms a buffer: (a) HCl + NaCl, (b) CH3COOH + CH3COONa?
Example 15
easy
In a buffer made from CH3COOH and CH3COO−, which component neutralizes added strong acid?
Example 16
hard
A 1.0 L buffer has 0.20 molHA (pKa=4.74) and 0.20 molA−. After adding 0.30 mol HCl, is the buffer still functioning, and what is the approximate pH?
Example 17
hard
A buffer contains 0.40 M phosphate as H2PO4− (pKa2=7.21) and 0.40 MHPO42−. After adding 0.10 mol HCl to 1.0 L, find the new pH.
Example 18
easy
Which pair forms a buffer: (a) HNO3+NaNO3, (b) HF+NaF?
Example 19
easy
Adding a buffer to pure water at pH 7 — does the buffer's pH always become 7?
Example 20
medium
Which buffer best holds pH 7.2: acetate (pKa=4.7), phosphate (pKa=7.2), or ammonia (pKa=9.2)?The best buffer for pH 7.2 is the one whose pKa is closest to 7.2 — phosphate.