What is pH buffer of 0.1 mol L-1 Na2HPO4/O.15 mol L-1 KH2PO4?
KH2PO4?
Given Ka(H2PO4-) = 6.2 x 10-8).
I would like to know the correct formula, steps for the answer
Thank you
pH = pKa + log [(base)/(acid)]
pH = 7.2 + log (0.1/0.15)
[H = 7.02.
Check my work.
Ah, pH buffers, those cheeky little things! Now, let's break this down and have some fun solving it.
Firstly, we need the Henderson-Hasselbalch equation for pH calculation, which is:
pH = pKa + log([A-]/[HA])
In this case, the acid is H2PO4-, and the conjugate base is HPO4^2-. So, let's call Na2HPO4 the base and KH2PO4 the acid.
Step 1: Calculate the pKa using the given Ka value:
pKa = -log10(Ka) = -log10(6.2 x 10^-8)
Step 2: Find the concentrations of the acid ([HA]) and base ([A-]):
Given that the base concentration is 0.1 mol L-1 Na2HPO4, we have [A-] = 0.1 mol L-1.
And the acid concentration is 0.15 mol L-1, so [HA] = 0.15 mol L-1.
Step 3: Plug the values into the Henderson-Hasselbalch equation and calculate the pH:
pH = pKa + log([A-]/[HA])
Now, I must warn you, math can be a bit of a clown sometimes, but we'll get through it together!
Plug in the values:
pH = (-log10(6.2 x 10^-8)) + log(0.1/0.15)
And after a little number juggling, you'll have your pH value.
Remember, it's always good to have a sense of humor when dealing with equations. Embrace the fun in math, my friend!
To calculate the pH buffer of a solution containing 0.1 mol/L Na2HPO4 and 0.15 mol/L KH2PO4, you can use the Henderson-Hasselbalch equation, which is given by:
pH = pKa + log([salt]/[acid])
where pKa is the negative logarithm of the acid dissociation constant (Ka), [salt] is the concentration of the salt (Na2HPO4 in this case), and [acid] is the concentration of the acid (KH2PO4 in this case).
1. Firstly, let's find the corresponding acid for the salt Na2HPO4. The formula of Na2HPO4 indicates that one of the hydrogen ions (H+) has been replaced by a sodium ion (Na+). So, the corresponding acid for Na2HPO4 is H2PO4-.
2. Next, we can plug the values into the Henderson-Hasselbalch equation. The pKa value for H2PO4- is given as 6.2 x 10^-8. Let's calculate the ratio of [salt] to [acid].
[salt] = 0.1 mol/L Na2HPO4
[acid] = 0.15 mol/L KH2PO4
[salt]/[acid] = (0.1/0.15) = 0.6667
3. Now, substitute the pKa value and the ratio into the Henderson-Hasselbalch equation.
pH = pKa + log([salt]/[acid])
= 6.2 x 10^-8 + log(0.6667)
4. Calculate the logarithm of the ratio using base 10 logarithm.
pH = 6.2 x 10^-8 + log(0.6667)
(Note: Make sure your calculator is set to use base 10 logarithms, usually denoted as "log" or "log10.")
By following these steps, you should be able to calculate the pH buffer of the given solution.
To calculate the pH of a buffer solution, you can use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-] / [HA])
Where:
pH is the desired pH of the buffer solution
pKa is the negative logarithm of the acid dissociation constant (Ka) of the acid
[A-] is the concentration of the conjugate base
[HA] is the concentration of the acid
In this case, you are given a mixture of Na2HPO4 and KH2PO4. Na2HPO4 is a salt of weak acid H2PO4-, and KH2PO4 is a salt of its conjugate base HPO42-.
First, you need to determine the major species in the buffer solution. Since Na2HPO4 is a strong electrolyte, it will completely dissociate into Na+ ions and HPO42- ions in solution. On the other hand, KH2PO4 will partially dissociate into K+ ions and H2PO4- ions.
Next, you need to calculate the concentrations of both the conjugate base (HPO42-) and the acid (H2PO4-) in the buffer solution.
The concentration of HPO42- can be calculated by multiplying the concentration of Na2HPO4 (0.1 mol/L) by the number of HPO42- ions produced when Na2HPO4 dissolves. Since there is one HPO42- ion for every Na2HPO4 molecule, the concentration of HPO42- is also 0.1 mol/L.
The concentration of H2PO4- can be calculated by considering the partial dissociation of KH2PO4. Since KH2PO4 is a salt of H2PO4-, it will produce an equal concentration of H2PO4-. Therefore, the concentration of H2PO4- is 0.15 mol/L.
Lastly, you can substitute the values into the Henderson-Hasselbalch equation:
pH = pKa + log ([A-] / [HA])
pH = pKa + log ([HPO42-] / [H2PO4-])
Given that the pKa of H2PO4- is 6.2 x 10-8, you can substitute the values:
pH = 6.2 x 10-8 + log (0.1 mol/L / 0.15 mol/L)
Now you can calculate the pH using a scientific calculator.