Chemistry · Acid · Base / Principles and Exploration
Acid strength and concentration — principles and investigation
Thick acid and strong acid have different meanings. Compare hydrogen ion concentration, pH, and dissociation degree by changing the analytical concentration and dissociation constant of the acid. The strength and concentration of the acid can be distinguished by dividing the case where the acid strength is different at the same concentration and the case where the same acid is diluted.
How does it work?
The strength of an acid is its tendency to dissociate, and the concentration is the amount of acid in a unit volume. It is classified as pH = −log₁₀[H⁺], α = [H⁺]/C.
Ka = x²/(C−x) · x = 2KaC/(√(Ka²+4KaC)+Ka)
Try this investigation
- Select a strong acid and a weak acid and change the concentration and Ka. In strong acids, the Ka adjustment value is not used in the calculation. A particle represents a proportion of 100 units of acid.
- Run and record weak and strong acids respectively at 0.100 mol/L. The weak acid Ka is set to 1.8×10⁻⁵.
- Record the case of lowering the concentration of weak acid to 0.010 mol/L and the case of increasing Ka to 9.0×10⁻⁵.
Interpreting your results
How do pH and dissociation change when the same weak acid is diluted?
If diluted at the same Ka, [H⁺] decreases and pH increases. At the same time, the dissociated ratio α of all acids increases. Ka is constant at the same temperature.
Assumptions and limitations
25℃ is the ideal concentration balance of monoprotic acid. For weak acids, use the exact solution x²+Kax−KaC=0. Activity and diversity assets are excluded. Auto-ionization of water is only ignored for [H⁺] ≥ 10⁻⁶ mol/L (sufficiently greater than 10⁻⁷). The entire input range satisfies this condition. Ka=1.8×10⁻⁵ is an example value for acetic acid. Particle ratios are rounded to the nearest 100.