The pKa of certain weak acid is 4.0. What should be the salt-to-acid ratio if we have to prepare a buffer with pH = 3 using the acid and of its salts?

Explanation

To prepare a buffer with a pH of 3 using a weak acid with a pKa of 4.0 and its corresponding salt, we need to consider the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]) In this equation, [A-] represents the concentration of the conjugate base (salt) and [HA] represents the concentration of the weak acid. Given that we want a pH of 3, we substitute the values into the equation: 3 = 4.0 + log([A-]/[HA]) Simplifying the equation: -1 = log([A-]/[HA]) To obtain the salt-to-acid ratio, we need to convert the logarithmic equation into an exponential form. In this case, we can rewrite it as: [A-]/[HA] = 10^(-1) Taking the logarithm base 10 of both sides: log([A-]/[HA]) = -1 From this equation, we can conclude that the salt-to-acid ratio should be 1:10 (or [A-]/[HA] = 1/10) in order to achieve a buffer with a pH of 3 using the weak acid and its salt.