Understanding the Concepts
* NaOH (Sodium Hydroxide): A strong base that completely dissociates in water, producing hydroxide ions (OH-) and sodium ions (Na+).
* pH: A measure of the acidity or basicity of a solution. It's calculated using the formula:
pH = -log[H+]
where [H+] is the concentration of hydrogen ions.
* pOH: A measure of the hydroxide ion concentration. It's calculated using the formula:
pOH = -log[OH-]
* Relationship between pH and pOH:
pH + pOH = 14
Calculations
1. 0.1 M NaOH
* Find [OH-]: Since NaOH completely dissociates, the concentration of OH- ions is equal to the concentration of NaOH, which is 0.1 M.
* Calculate pOH:
pOH = -log(0.1) = 1
* Calculate pH:
pH = 14 - pOH = 14 - 1 = 13
Therefore, the pH of 0.1 M NaOH is 13.
2. 0.05 M NaOH
* Find [OH-]: The concentration of OH- ions is equal to the concentration of NaOH, which is 0.05 M.
* Calculate pOH:
pOH = -log(0.05) = 1.3
* Calculate pH:
pH = 14 - pOH = 14 - 1.3 = 12.7
Therefore, the pH of 0.05 M NaOH is 12.7.
Key Points
* NaOH solutions have a high pH due to the presence of a high concentration of hydroxide ions (OH-).
* The higher the concentration of NaOH, the higher the pH.
* Strong bases like NaOH completely dissociate in water, making the calculations straightforward.
