Calculate the pH of the following solutions: (c) 0.075 M NaOH

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Identify that NaOH is a strong base, which means it dissociates completely in water to produce OH⁻ ions.

Write the dissociation equation for NaOH: \[ \text{NaOH} \rightarrow \text{Na}^+ + \text{OH}^- \]

Determine the concentration of OH⁻ ions, which is equal to the initial concentration of NaOH, 0.075 M, because it dissociates completely.

Use the formula for pOH: \[ \text{pOH} = -\log[\text{OH}^-] \] to calculate the pOH of the solution.

Convert pOH to pH using the relationship: \[ \text{pH} = 14 - \text{pOH} \].

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, values below 7 indicate acidic solutions, and values above 7 indicate basic solutions. The scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.

Strong Bases

Strong bases, like sodium hydroxide (NaOH), completely dissociate in water to produce hydroxide ions (OH-). This complete dissociation means that the concentration of hydroxide ions in the solution is equal to the concentration of the base. Understanding this concept is crucial for calculating the pH of basic solutions.

Calculating pH from pOH

To find the pH of a basic solution, one can first calculate the pOH using the formula pOH = -log[OH-]. Since pH and pOH are related by the equation pH + pOH = 14, once the pOH is determined, the pH can be easily calculated. This relationship is essential for converting between the two measures of acidity and basicity.

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