Each of the following solutions has a concentration of 0.1 mol/L. Compare the hydronium ion concentration and pH in each pair and explain why they are different.
a) H2SO4(aq) vs. H2SO3(aq)
b) H2S(aq) vs. NH3(aq)
Thanks, solved it.
a) H2SO4(aq) vs. H2SO3(aq)
To compare the hydronium ion concentration and pH in each pair, we need to consider the strength of the acids involved.
H2SO4 is a stronger acid compared to H2SO3. It is a strong acid and completely dissociates in water to release H+ ions. Therefore, the concentration of hydronium ions (H3O+) will be higher in H2SO4(aq) solution compared to H2SO3(aq).
On the other hand, H2SO3 is a weak acid and only partially dissociates in water. Consequently, the concentration of hydronium ions (H3O+) will be lower in H2SO3(aq) solution compared to H2SO4(aq).
As for pH, which is a measure of the concentration of hydronium ions, the lower the pH, the higher the concentration of hydronium ions. Therefore, H2SO4(aq) will have a lower pH compared to H2SO3(aq) because it has a higher concentration of hydronium ions.
b) H2S(aq) vs. NH3(aq)
To compare the hydronium ion concentration and pH in each pair, we need to consider whether the substances are acids or bases.
H2S is an acid, while NH3 is a base. When H2S is dissolved in water, it will partially dissociate to release H+ ions, resulting in an increase in the concentration of hydronium ions (H3O+). Therefore, H2S(aq) will have a higher concentration of hydronium ions compared to NH3(aq).
NH3, on the other hand, is a weak base and only partially accepts H+ ions from water. As a result, the concentration of hydronium ions (H3O+) will be lower in NH3(aq) compared to H2S(aq).
Regarding pH, the higher the concentration of hydronium ions, the lower the pH. Therefore, H2S(aq) will have a lower pH compared to NH3(aq) due to its higher concentration of hydronium ions.
To compare the hydronium ion concentration and pH in each pair of solutions, we need to consider the dissociation of each compound in water.
a) H2SO4(aq) vs. H2SO3(aq):
H2SO4 is a strong acid, meaning it completely dissociates in water. It splits into two H+ ions and one SO4^2- ion. Therefore, for every mole of H2SO4 dissolved, we will have two moles of H+ ions.
On the other hand, H2SO3 is a weak acid, meaning it only partially dissociates in water. It forms one H+ ion and one HSO3- ion. Therefore, for every mole of H2SO3 dissolved, we will have one mole of H+ ions.
Since the concentration of both solutions is 0.1 mol/L, the hydronium ion concentration for H2SO4 is 0.2 mol/L (twice the concentration), while the hydronium ion concentration for H2SO3 is 0.1 mol/L.
pH is a measure of the acidity of a solution and is defined as the negative logarithm of the hydronium ion concentration. So, using the formula pH = -log[H+], we can calculate the pH for each solution.
For H2SO4: pH = -log(0.2) ≈ 0.70 (since log(0.2) is approximately -0.70).
For H2SO3: pH = -log(0.1) = 1.
Therefore, the hydronium ion concentration and pH are different because H2SO4 is a stronger acid than H2SO3, resulting in a higher concentration of hydronium ions and a lower pH.
b) H2S(aq) vs. NH3(aq):
H2S is a weak acid, and NH3 is a weak base. They both undergo partial dissociation in water.
H2S dissociates into H+ and HS- ions, while NH3 dissociates into NH4+ and OH- ions.
So for every mole of H2S dissolved, we will have one mole of H+ ions, and for every mole of NH3 dissolved, we will have one mole of NH4+ ions.
The hydronium ion concentration in both solutions will be 0.1 mol/L.
pH = -log(0.1) = 1.
Therefore, the hydronium ion concentration and pH are the same for both H2S and NH3 solutions since they have the same concentration and undergo partial dissociation.