to make an acid buffer of pH 5, what will be the ratio of salt to acid in the solution.
[Ka= 1.8x10^-5 mol.dm^3]
To determine the ratio of salt to acid required to create an acid buffer of pH 5, we need to use the Henderson-Hasselbalch equation.
The Henderson-Hasselbalch equation is given as:
pH = pKa + log ([salt]/[acid])
Where pH is the desired pH of the buffer, pKa is the negative logarithm of the acid dissociation constant (Ka), [salt] is the concentration of the salt, and [acid] is the concentration of the acid in the buffer solution.
In this case, we want to create a buffer with a pH of 5, and the Ka value (acid dissociation constant) is given as 1.8x10^-5 mol.dm^3.
Rearranging the Henderson-Hasselbalch equation, we have:
pKa = pH - log ([salt]/[acid])
Substituting the given values, we get:
log ([salt]/[acid]) = 5 - log (1.8x10^-5)
Now, if we take the antilog (inverse logarithm) of both sides, we get:
([salt]/[acid]) = 10^(5 - log (1.8x10^-5))
Calculating the right-hand side of the equation:
([salt]/[acid]) = 10^(5 - (-5 + log10(1.8)))
([salt]/[acid]) = 10^(5 + 5 - log10(1.8))
([salt]/[acid]) = 10^(10 - log10(1.8))
Now, using a calculator, evaluate the value of 10^(10 - log10(1.8)), which is approximately 63.096.
Therefore, the ratio of salt to acid in the buffer solution to achieve a pH of 5 is approximately 63.096:1.