A solution with a pH of 7.0: (Choose all that apply) Group of answer choices would have an equal number of hydrogen and hydroxide ions. would have fewer hydrogen ions than hydroxide ions. would be an acid solution. would be considered neutral
The Correct Answer and Explanation is:
The correct answer is:
Would have an equal number of hydrogen and hydroxide ions.
Would be considered neutral.
Explanation:
The pH scale ranges from 0 to 14 and is a measure of the hydrogen ion concentration ([H+]) in a solution. A solution with a pH of 7.0 is considered neutral, meaning it is neither acidic nor basic.
- Equal number of hydrogen and hydroxide ions:
At a pH of 7.0, the concentration of hydrogen ions ([H+]) is equal to the concentration of hydroxide ions ([OH-]). This happens because water itself (H₂O) dissociates into H+ and OH- ions in equal amounts:
H2O⇌H++OH−H_2O \rightleftharpoons H^+ + OH^-H2O⇌H++OH−
For pure water or neutral solutions, the concentration of both H+ and OH- ions is 1×10−71 \times 10^{-7}1×10−7 M (molar). Therefore, at pH 7, the solution has an equal number of hydrogen and hydroxide ions. - Would be considered neutral:
A solution with a pH of 7 is defined as neutral because it has an equal concentration of hydrogen ions and hydroxide ions, with neither dominating. This is the baseline or reference point for the pH scale. If the pH is less than 7, the solution is acidic, and if it’s greater than 7, it’s alkaline (basic).
Why the other choices are incorrect:
- Would have fewer hydrogen ions than hydroxide ions:
This statement applies to basic (alkaline) solutions, where the concentration of OH- ions is higher than H+ ions. In a neutral solution (pH 7), the concentrations of H+ and OH- are the same, so this is not true for a pH of 7. - Would be an acid solution:
Acidic solutions have a pH less than 7, which indicates a higher concentration of hydrogen ions (H+) than hydroxide ions. Since a pH of 7 indicates neutrality, this statement is incorrect for a solution with pH 7.
