What are the concentrations of H3O+ and OH- and what is the pH of a 0.15 M solution of Na2CO3 (at 25 °C).
[h3o] = 1.78x10 ^-1
[OH] = 5.61x10^-3
pH= 11.75
The pH is determined by the hydrolysis of the CO3^-2.
CO3^-2 + HOH ==> HCO3^- + OH^-
Khydrolysis = Kb for carbonate ion = (Kw/K2 for HCO3^-)= (HCO3^-)(OH^-)/(HCO3^-).
Prepare and ICE chart, substitute into the Kb expression above and solve for OH-, pOH, the pH.
To determine the concentrations of H3O+ and OH- in a solution of Na2CO3, we need to understand the chemical reaction that occurs when Na2CO3 dissolves in water.
Na2CO3 dissociates in water to form Na+ and CO32-. The CO3 2- ion can react with water in a hydrolysis reaction, resulting in the formation of HCO3- (bicarbonate) and OH- ions.
The chemical equation for this reaction is:
CO3^2- + H2O ⇌ HCO3- + OH-
From the equation, we can see that for every one CO3^2- ion that reacts with water, one HCO3- ion and one OH- ion are formed.
Since Na2CO3 is a strong electrolyte, it undergoes complete dissociation in water, meaning that all the Na2CO3 molecules dissociate into Na+ and CO3^2- ions.
Therefore, in a 0.15 M solution of Na2CO3, the concentration of CO3^2- ions is also 0.15 M. As explained above, for every one CO3^2- ion that reacts with water, one OH- ion is formed. So the concentration of OH- ions is also 0.15 M.
In pure water at 25 °C, the concentration of H3O+ and OH- ions is 1 × 10^-7 M. However, in the presence of other ions, such as in the case of our Na2CO3 solution, the concentration of H3O+ and OH- ions can be affected.
Based on the formation of OH- ions from the reaction between CO3^2- and water, we can deduce that the concentration of H3O+ ions will be lower than 1 × 10^-7 M. However, without further information, we cannot determine the exact concentration of H3O+ ions in the solution.
To find the pH of the solution, we need the concentration of H3O+ ions. Since we don't have that information, we cannot calculate the pH of the solution at this time.