Formula Sheet for pH Calculations and Buffer Solutions

This page presents a concise collection of formulas crucial for pH Calculations A Level Chemistry AQA and OCR a level chemistry buffers questions. The formulas cover various aspects of acid-base chemistry and buffer solutions, essential for Module 5 acids bases buffers ph sheet pdf.

The sheet begins with the fundamental pH equation:

Definition: pH = -log₁₀ [H⁺]

This formula is the cornerstone of pH calculations, relating the hydrogen ion concentration to the pH value.

For strong acids, a simplified approach is provided:

Highlight: [H⁺] = [acid]

This equality holds true for strong acids due to their complete dissociation in solution.

The sheet also includes the water dissociation constant (Kw) and its relationship with hydrogen and hydroxide ion concentrations:

Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ (at 25°C)

Example: To calculate [OH⁻] when [H⁺] is known, use [OH⁻] = Kw / [H⁺]

For weak acids, the acid dissociation constant (Ka) is introduced:

Ka = [H⁺]² / [HA]

This leads to the formula for calculating hydrogen ion concentration in weak acid solutions:

[H⁺] = √(Ka × [HA])

Vocabulary: pKa is the negative logarithm of Ka, expressed as pKa = -log₁₀Ka

The formula sheet also covers buffer solutions, which are crucial for Buffer Calculations A level Chemistry OCR:

For a buffer composed of a weak acid and its conjugate base salt:

[H⁺] = Ka × [HA] / [A⁻]

Highlight: The ICEE method is mentioned for pH calculations of buffers formed by mixing weak acids with bases, though the specific steps are not detailed on this sheet.

This comprehensive formula sheet serves as an excellent resource for students preparing for OCR A Level chemistry module 5 practice questions answers and tackling Acid and base calculations pdf problems. It covers the essential equations needed for a wide range of pH and buffer calculations, making it an invaluable tool for Pmt OCR A level Chemistry module 5 revision.