pH test

Sample: Pure Distilled Water

Red

Blue

Measured pH

7.0

NEUTRAL

Continuous pH Range Control pH 0.0 (Strong Acid) to 14.0 (Strong Base)

pH 0 3 5 7 (Neutral) 9 11 pH 14

15 Common Sample Presets: Click preset to load

Active Chemical Indicator pH 0 – 14

Microscopic Particle Simulation

$H_3O^+$ $OH^-$

[H₃O⁺] Hydronium Ion

1.0 × 10⁻⁷ M

[OH⁻] Hydroxide Ion

1.0 × 10⁻⁷ M

Level Profile Snapshot

Interactive Lab Challenge

Mystery Unknown Solution Diagnostic

Test the unknown liquid with chemical indicators, deduce its pH level, and identify the substance.

Mystery Flask #Alpha

Test with Indicators:

Select an indicator above to observe color reaction.

Submit Your Diagnostic Conclusion

Estimated pH Level (0 - 14):

Identified Substance:

The Chemistry of pH & Chemical Indicators

pH (potential of Hydrogen) quantifies the acidity or basicity of an aqueous solution by measuring hydronium ion concentration on a logarithmic scale.

Logarithmic Scale

$$pH = -\log_{10}[H_3O^+]$$

A change of 1 pH unit represents a 10-fold difference in $[H_3O^+]$. pH 3 is 10 times more acidic than pH 4, and 1,000 times more acidic than pH 6.

Water Self-Ionization

$$K_w = [H_3O^+][OH^-] = 1.0 \times 10^{-14}$$

At 25°C in pure neutral water, $[H_3O^+] = [OH^-] = 1.0 \times 10^{-7}\text{ M}$, resulting in $pH = 7.0$ and $pOH = 7.0$. The sum of $pH + pOH$ always equals 14.

Indicator Equilibrium

$$HIn \rightleftharpoons H^+ + In^-$$

Indicators are weak acids ($HIn$) whose protonated form absorbs different visible light wavelengths than its conjugate base form ($In^-$). Transition occurs around $pH = pK_a \pm 1$.

Summary Comparison Matrix of Key Indicators

Indicator	Effective pH Range	pK_a	Acid Form Color ($HIn$)	Base Form Color ($In^-$)	Primary Applications
Universal Indicator	0.0 – 14.0	N/A (Mixture)	Red	Violet	General laboratory screening across full range
Phenolphthalein	8.2 – 10.0	9.4	Colorless	Deep Magenta Pink	Strong acid / strong base titration end-point detection
Litmus Paper	4.5 – 8.3	6.5	Red Paper	Blue Paper	Quick qualitative acid-vs-base field test
Red Cabbage (Anthocyanin)	1.0 – 14.0	Multiple (Flavin)	Red / Pink	Green / Yellow	Eco-friendly natural indicator, classroom demonstrations