A small amount of sodium hydroxide is added to water. When the chemical reaction reaches equilibrium, the pH is 12. Which statement and conclusion about sodium hydroxide is correct?(1 point)
Responses
The negative log of the concentration of OH– ions is 12. Sodium hydroxide is a strong base.
The negative log of the concentration of OH – ions is 12. Sodium hydroxide is a strong base.
The negative log of the concentration of OH– ions is 2. Sodium hydroxide is a strong base.
The negative log of the concentration of OH – ions is 2. Sodium hydroxide is a strong base.
The negative log of the concentration of OH– ions is 2. Sodium hydroxide is a strong acid.
The negative log of the concentration of OH – ions is 2. Sodium hydroxide is a strong acid.
The negative log of the concentration of OH– ions is 12. Sodium hydroxide is a strong acid.
The correct statement and conclusion about sodium hydroxide is:
The negative log of the concentration of OH– ions is 12. Sodium hydroxide is a strong base.
Note that the product of the H3O+ and OH− ion concentrations always equals 10−14mol/L. This is because pure water naturally undergoes a reversible reaction in which H2O breaks into H+ and OH− (The H+ attaches itself to an H2O creating H3O+) at a rate that leaves the product of these ions’ concentrations equal to 10−14 mol/L. In pure water, H3O+ and OH− have equal concentrations of 1.0 x 10−7 mol/L (hence water’s pH = −log(1.0 x 10−7) = 7).
The statement provided is correct. In pure water, the concentration of H3O+ and OH- ions are equal, with a concentration of 1.0 x 10^-7 mol/L. This is because of the reversible reaction in which water breaks into H+ and OH- ions. The product of the H3O+ and OH- ion concentrations in water is always 10^-14 mol/L. Therefore, the pH of pure water is 7.
Use the following information to answer the original question.
Values on the pH scale are defined in relation to the H3O+ concentration in mol/L. The pH scale is a logarithmic scale, where the values are equal to the negative of the base ten logarithm of the H3O+ concentration in mol/L. (In other words, if you write the H3O+ concentration as a power of 10, then the pH is the absolute value of the exponent.)
Based on the given information, we know that the pH is defined as the negative logarithm of the H3O+ concentration in mol/L. Since sodium hydroxide is a strong base, it will dissociate completely in water and produce OH- ions. Therefore, the concentration of OH- ions will be equal to the concentration of sodium hydroxide.
In the question, it states that when the chemical reaction reaches equilibrium, the pH is 12. Therefore, the negative logarithm of the concentration of OH- ions will also be 12.
Answer: The negative log of the concentration of OH– ions is 12. Sodium hydroxide is a strong base.
Does the water affect this at all?
Yes, the presence of water does affect the concentration of OH- ions and consequently the pH value. When water is present, it naturally undergoes a reversible reaction where water molecules break apart into H+ and OH- ions.
In pure water, the concentration of H+ and OH- ions are equal, resulting in a neutral pH of 7. However, when sodium hydroxide (NaOH) is added to water, the sodium hydroxide dissociates completely into Na+ and OH- ions. This increases the concentration of OH- ions in the solution.
Since the pH scale is defined in relation to the H3O+ (or H+) concentration, the increase in OH- concentration will cause a decrease in the H+ concentration. As a result, the pH of the solution will increase. In the given scenario, when the reaction reaches equilibrium, the pH is measured to be 12.
Therefore, the presence of water does affect the pH value in this case, as it influences the concentrations of both H+ and OH- ions.
Does this change your answer at all?
I apologize for any confusion caused. Based on the information provided in your original question, the presence of water does not affect the answer. The pH scale is based on the H3O+ concentration in mol/L, which is determined by the dissociation of substances in water. In the case of sodium hydroxide, it dissociates completely into Na+ and OH- ions when added to water. The concentration of OH- ions in the solution will determine the pH, and in the given scenario where the pH is 12, it indicates a high concentration of OH- ions.
Therefore, my previous answer stating that "The negative log of the concentration of OH– ions is 12. Sodium hydroxide is a strong base" remains correct. The presence of water does not change this conclusion.