Calculate Ph of 0.005m Naoh

This guide explains how to calculate the pH of a 0.005 molar sodium hydroxide (NaOH) solution. We'll cover the calculation formula, provide a worked example, and discuss how to interpret the results.

How to Calculate pH of 0.005M NaOH

Calculating the pH of a sodium hydroxide (NaOH) solution involves understanding the relationship between concentration and pH. Sodium hydroxide is a strong base, which means it completely dissociates in water to produce hydroxide ions (OH⁻).

Key Point: For strong bases like NaOH, the concentration of hydroxide ions ([OH⁻]) is equal to the molar concentration of the solution.

The steps to calculate the pH are:

Determine the concentration of hydroxide ions ([OH⁻]) in moles per liter (M).
Calculate the pOH using the formula: pOH = -log[OH⁻].
Convert pOH to pH using the relationship: pH = 14 - pOH.

For a 0.005M NaOH solution:

The [OH⁻] is equal to the concentration of NaOH, which is 0.005 M.
Calculate pOH = -log(0.005).
Calculate pH = 14 - pOH.

pH Calculation Formula

The pH of a strong base solution can be calculated using the following steps:

Step 1: Determine [OH⁻]

For a strong base like NaOH, the concentration of hydroxide ions is equal to the molar concentration of the solution:

[OH⁻] = Molarity of NaOH

Step 2: Calculate pOH

The pOH is calculated using the negative logarithm (base 10) of the hydroxide ion concentration:

pOH = -log[OH⁻]

Step 3: Calculate pH

The pH is calculated using the relationship between pH and pOH:

pH = 14 - pOH

These formulas are based on the fact that water dissociates into equal concentrations of H⁺ and OH⁻ ions, giving a neutral pH of 7. The sum of pH and pOH is always 14.

Worked Example

Let's calculate the pH of a 0.005M NaOH solution step by step.

Step 1: Determine [OH⁻]

The concentration of hydroxide ions is equal to the molar concentration of NaOH:

[OH⁻] = 0.005 M

Step 2: Calculate pOH

Using the pOH formula:

pOH = -log(0.005)

pOH ≈ -(-2.3010) = 2.3010

Step 3: Calculate pH

Using the pH formula:

pH = 14 - pOH

pH = 14 - 2.3010 = 11.6990

Final Result

The pH of a 0.005M NaOH solution is approximately 11.70.

This calculation shows that a 0.005M NaOH solution is strongly alkaline, which is expected for a strong base.

Interpreting the Result

The pH of 11.70 indicates that the solution is strongly alkaline. Here's what this means:

The solution has a high concentration of hydroxide ions (OH⁻).
It will react strongly with acids and neutralize them.
It will turn red litmus paper blue and react with indicators that change color in alkaline solutions.

Important Note: The pH scale ranges from 0 (very acidic) to 14 (very alkaline). A pH of 7 is neutral. Values below 7 are acidic, and values above 7 are alkaline.

For comparison, here's a table showing the pH ranges for different types of solutions:

pH Range	Solution Type	Example
0-3	Very Strong Acid	Battery acid, stomach acid
4-6	Weak Acid	Vinegar, citrus fruits
7	Neutral	Pure water, distilled water
8-10	Weak Base	Soap, baking soda
11-14	Strong Base	NaOH, drain cleaner

FAQ

What is the pH of a 0.005M NaOH solution?: The pH of a 0.005M NaOH solution is approximately 11.70.
Why is the pH of NaOH solutions high?: NaOH is a strong base that completely dissociates in water, producing a high concentration of hydroxide ions (OH⁻), which results in a high pH.
How does the concentration of NaOH affect the pH?: For strong bases like NaOH, the pH increases as the concentration increases. A higher concentration of NaOH means more hydroxide ions are produced, resulting in a higher pH.
What is the relationship between pH and pOH?: The sum of pH and pOH is always 14. This is because water dissociates into equal concentrations of H⁺ and OH⁻ ions, giving a neutral pH of 7.
How can I verify the pH calculation?: You can verify the calculation by using a pH meter or pH test strips to measure the pH of a known concentration of NaOH solution. The measured pH should be close to the calculated value.