What is the pH of the buffer system after the addition of 0.10 mole of gaseous HCl to 1 L of the solution. With a buffer system containing 1.0 M CH3COOH and 1.0 M CH3COONa.
Well, if you were hoping for a punchline, I apologize in advance because pH calculations can be a bit of a buzzkill. But don't worry, I'll do my best to make it a little less boring!
To determine the pH of our buffer system after the addition of gaseous HCl, we need to consider the acid-base reaction that occurs. In this case, the HCl reacts with CH3COONa to form more CH3COOH.
Now, since both CH3COOH and CH3COONa are part of a buffer system, they work together to resist changes in pH. In other words, they're like a comedy duo that sticks together no matter what!
As for the calculation itself, we need to consider the Henderson-Hasselbalch equation:
pH = pKa + log ([A-]/[HA])
In this case, CH3COOH (acetic acid) is HA and CH3COONa (sodium acetate) is A-. The pKa of acetic acid is 4.74.
Now, after the addition of HCl, we'll have some extra CH3COOH. So, we need to figure out how much CH3COOH and CH3COONa are left in the solution.
Since we have equal amounts of CH3COOH and CH3COONa initially (1 mole each), and we add 0.10 mole of HCl, we'll have 1.10 moles of CH3COOH and 0.90 moles of CH3COONa.
Plugging these values into the Henderson-Hasselbalch equation, we get:
pH = 4.74 + log (0.90/1.10)
Now go ahead, grab your calculator, and solve this equation. Trust me, I won't attempt any clown math tricks here!
Once you have the result, you'll find out the pH of the buffer system after the addition of HCl. Good luck, pH master!
To determine the pH of the buffer system after the addition of HCl, we need to follow the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
1. Identify the relevant components:
- Acid (HA): CH3COOH (acetic acid)
- Conjugate base (A-): CH3COO- (acetate ion)
2. Calculate the pKa value:
The pKa value for acetic acid is usually given as 4.76.
3. Calculate the initial concentrations of the acid and conjugate base:
The initial concentration of CH3COOH is 1.0 M.
The initial concentration of CH3COONa is also 1.0 M since it dissociates into CH3COO-.
4. Determine the change in concentration of the conjugate base (A-) due to the addition of HCl:
When 0.10 mole of HCl is added to 1 L of the solution, it reacts with the CH3COONa and converts it into CH3COOH.
Since the concentration of CH3COONa is the same as CH3COO-, the concentration of CH3COO- decreases by 0.10 M.
5. Determine the new concentrations of CH3COOH and CH3COO-:
The concentration of CH3COOH remains the same (1.0 M).
The concentration of CH3COO- decreases by 0.10 M (from 1.0 M to 0.90 M).
6. Calculate the pH using the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
pH = 4.76 + log(0.90/1.0)
Using a scientific calculator or software, evaluate log(0.90/1.0) to get the final answer.
Note: The final answer will depend on the exact pKa value and the concentration values used in the calculation.
To determine the pH of the buffer system after the addition of 0.10 mole of gaseous HCl, we need to consider the reaction between the added acid (HCl) and the components of the buffer system (CH3COOH and CH3COONa).
First, let's write down the chemical equation for the reaction between HCl and CH3COOH:
HCl + CH3COOH ⇌ CH3COOH2+ + Cl-
In the buffer system, CH3COOH acts as a weak acid (acetic acid) and CH3COO- (from CH3COONa) acts as a conjugate base.
Since the buffer system is made up of equal concentrations of acetic acid (CH3COOH) and its conjugate base (CH3COONa), the ratio of their concentrations will remain constant. This means that the buffer system can resist changes in pH when limited amounts of acid (like HCl) or base (like NaOH) are added.
Now, let's consider the reaction between HCl and CH3COO-:
HCl + CH3COO- → CH3COOH + Cl-
In this reaction, HCl reacts with CH3COO- to form CH3COOH, which is the weak acid component of the buffer system. As a result, the concentration of CH3COOH will increase, while the concentration of CH3COO- will decrease. However, the ratio of their concentrations will remain constant, keeping the buffer system effective.
To calculate the pH, we need to determine the concentrations of CH3COOH and CH3COO- after the addition of HCl. The initial concentration of CH3COOH is 1.0 M, and the concentration of CH3COONa is also 1.0 M.
Since 0.10 mole of HCl is added to 1 L of the buffer solution, we can assume that all of the HCl will react with CH3COO-. This means that the final concentration of CH3COO- will be reduced by 0.10 M.
Therefore, the final concentration of CH3COO- will be 1.0 M - 0.10 M = 0.90 M.
Since the ratio of CH3COOH to CH3COO- in the buffer system remains constant (1:1), the concentration of CH3COOH will also be 0.90 M.
To determine the pH, we need to use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
In this case, [A-] represents the concentration of CH3COO- and [HA] represents the concentration of CH3COOH.
The pKa of acetic acid (CH3COOH) is typically around 4.75.
Plugging in the values:
pH = 4.75 + log(0.90/0.90) = 4.75
Therefore, the pH of the buffer system after the addition of 0.10 mole of gaseous HCl to 1 L of the solution is approximately 4.75.
CH3COOH is the acid.
CH3COONa is the base.
Buffer systems work because the acid uses up any base added and the base uses up any acid added. HCl is being added(0.1 mols to 1L or 0.1 M) so the reaction will be with the base, as follows:
......................CH3COONa + HCl ==>CH3COOH + NaCl
Initial...................1 M...............0...............1 M............0
add........................................0.1............
Change............-0.1...............-0.1...............+0.1.
Equilibrium........0.9...................0................1.1
Substitute the E line into the HH equation and solve for pH. Post your work if you get stuck. You should confirm this but I think pKa for CH3COOH is 4.75.
pH = pKa + log[(CH3COONa)/(CH3COOH)]