An aqueous solution of (NH4)2SO4 has a pH lower than 7. Explain this observation.
Thanks! :)
Write the equation for the hydrolysis of the NH4^+.
NH4^+ + H2O ==> NH3 + H3O^+
That should help. pH<7 is an acid solution, right? And what's being produced by the hydrolysis?
To explain why an aqueous solution of (NH4)2SO4 has a pH lower than 7, we need to understand the nature of the compound and its interaction with water molecules.
(NH4)2SO4 is the chemical formula for ammonium sulfate, which is a salt composed of ammonium ions (NH4+) and sulfate ions (SO42-). When this salt is dissolved in water, it dissociates into its component ions.
The ammonium ion, NH4+, has properties of a weak acid. It can donate a proton (H+) to water, resulting in the formation of hydronium ions (H3O+). This process can be represented as follows:
NH4+ + H2O -> H3O+ + NH3
The hydronium ions in the solution contribute to the acidity, contributing to a decrease in pH.
On the other hand, the sulfate ion, SO42-, does not significantly affect the pH of the solution. It is a weak base and does not react with water to form hydroxide ions (OH-). Therefore, the acidity of the solution is mainly determined by the presence of the ammonium ions, resulting in a lower pH value than 7.
In summary, the pH of the aqueous solution of (NH4)2SO4 is lower than 7 due to the presence of ammonium ions (NH4+), which act as a weak acid and generate hydronium ions (H3O+) when dissolved in water.