Question

What are the major species in solution after ${\mathrm{NaHSO}}_4$ is dissolved in water? What happens to the $\mathrm{pH}$ of the solution as more ${\mathrm{NaHSO}}_4$ is added? Why? Would the results vary if baking soda $\left({\mathrm{NaHCO}}_3\right)$ were used instead?

Short answer

When NaHSO4 is dissolved in water, the major species present are Na+, HSO4-, H+, and OH-. The solution is initially acidic due to HSO4- dissociation. As more NaHSO4 is added, the solution becomes more acidic due to an increase in H+ ions. On the other hand, if NaHCO3 (baking soda) were used instead, the resulting solution would be less acidic because HCO3- ions can act as both weak acid and weak base, neutralizing some H+ ions.

Step-by-step solution

When sodium hydrogen sulfate (NaHSO4) is dissolved in water, it dissociates into its constituent ions: sodium (Na+) and hydrogen sulfate (HSO4-). Water itself can also dissociate to a small extent, forming hydrogen (H+) and hydroxide (OH-) ions. Therefore, the major species in the solution would be Na+, HSO4-, H+, and OH-. #Step 2: Determine initial acidity or basicity of the NaHSO4 solution#

HSO4- is a weak acid because it can donate a proton (H+) to the solution. As HSO4- dissociates, it forms H+ and SO4^2- ions. The initial NaHSO4 solution would therefore have an acidic pH because of the acid dissociation. #Step 3: Analyze the effect of adding more NaHSO4 on the pH#

When more NaHSO4 is added to the solution, it will dissociate and increase the concentration of HSO4- ions. As HSO4- ion concentration increases, so does its dissociation into H+ and SO4^2-, causing the concentration of H+ ions to rise. The pH of the solution, which is defined as $-\log [{\mathrm{H}}^{+}]$ in water, will decrease (become more acidic) due to an increase in H+ ions. #Step 4: Compare the results with sodium hydrogen carbonate (NaHCO3)#

Now, let's analyze what would happen if sodium hydrogen carbonate (baking soda) or NaHCO3 is used instead. When NaHCO3 dissolves in water, it dissociates into Na+ and HCO3- ions. The HCO3- ion can both donate and accept protons; it can act as both a weak acid and a weak base. Since it can act as a weak base, adding NaHCO3 to the solution can neutralize some of the H+ ions present due to the dissociation of HSO4- ions. Consequently, the solution's acidity will decrease, and its pH will increase, meaning it would be less acidic in comparison to the NaHSO4 solution. In summary: 1. The major species in the NaHSO4 solution are Na+, HSO4-, H+, and OH-. 2. The initial NaHSO4 solution is acidic. 3. Adding more NaHSO4 makes the solution more acidic due to an increase in H+ ions. 4. If baking soda (NaHCO3) were used instead, the resulting solution would be less acidic than the original NaHSO4 solution due to its weak acid/base properties.