16 Calculate The Ph of 0.0075 M Sr Oh 2

Strontium hydroxide (Sr(OH)₂) is a strong base that dissociates completely in water. Calculating its pH involves understanding the relationship between concentration and pH for strong bases. This guide explains the calculation process, provides a working example, and helps you interpret the results.

How to Calculate the pH of Sr(OH)₂

Calculating the pH of a strong base solution like Sr(OH)₂ involves these key steps:

Determine the concentration of the hydroxide ions (OH⁻) in the solution.
Calculate the pOH using the hydroxide ion concentration.
Convert pOH to pH using the relationship pH + pOH = 14.

For Sr(OH)₂, which completely dissociates in water, the concentration of OH⁻ ions equals the concentration of Sr(OH)₂.

The pH Calculation Formula

The pH of a strong base solution can be calculated using these formulas:

[OH⁻] = [Sr(OH)₂] (since Sr(OH)₂ is a strong base) pOH = -log[OH⁻] pH = 14 - pOH

Where:

[OH⁻] is the concentration of hydroxide ions in moles per liter (M)
[Sr(OH)₂] is the concentration of strontium hydroxide in moles per liter (M)
pOH is the negative logarithm of the hydroxide ion concentration
pH is the negative logarithm of the hydrogen ion concentration

Worked Example

Let's calculate the pH of a 0.0075 M Sr(OH)₂ solution:

First, note that [OH⁻] = [Sr(OH)₂] = 0.0075 M
Calculate pOH: pOH = -log(0.0075) ≈ 2.123
Calculate pH: pH = 14 - pOH ≈ 14 - 2.123 = 11.877

The pH of a 0.0075 M Sr(OH)₂ solution is approximately 11.88.

Note: The calculator uses more precise logarithmic calculations for accurate results.

Interpreting the Results

A pH of 11.88 indicates a strongly alkaline solution. This means:

The solution is highly basic and would feel slippery to the skin
It would turn red litmus paper blue
It would react with acids to form water and a salt

For comparison, household ammonia has a pH around 11-12, while oven cleaner is typically around 13-14.

Frequently Asked Questions

Why does Sr(OH)₂ dissociate completely in water?: Strontium hydroxide is a strong base, meaning it completely dissociates into Sr²⁺ and OH⁻ ions in aqueous solution.
What happens if the concentration of Sr(OH)₂ changes?: The pH will change proportionally. Higher concentrations result in higher pH values (more alkaline).
Can this calculator be used for other strong bases?: Yes, the same principles apply to other strong bases like NaOH or KOH, as they also dissociate completely in water.
What is the difference between pH and pOH?: pH measures the concentration of hydrogen ions (H⁺), while pOH measures the concentration of hydroxide ions (OH⁻). They are related by the equation pH + pOH = 14.