pH Determination of Common Solutions using Universal Indicator
What you will learn
Determine the pH values of various everyday and laboratory solutions (lemon juice, vinegar, saliva, baking soda, NaOH, HCl) using pH paper strips and a calibrated pH meter.
Materials needed
- Broad-range Universal Indicator Paper strips with standard color chart boxWhat is it?Broad-range Universal Indicator Paper strips with standard color chart box₹50
Full range universal indicator solution and calibrated pH test strips (pH 1 – 14).
Specifications- pH Range
- 1.0 to 14.0 full spectrum
- Indicator Formula
- Thymol blue, methyl red, bromothymol blue, phenolphthalein
- Color Chart
- Gloss laminated 14-step color comparator
- Format
- Booklet of 100 test strips + 100 mL dropper bottle
- Test solutions: Dilute HCl, Dilute NaOH, Ethanoic acid (vinegar), Lemon juice, NaHCO3 solution, Distilled water mL eachWhat is it?Test solutions: Dilute HCl, Dilute NaOH, Ethanoic acid (vinegar), Lemon juice, NaHCO3 solution, Distilled water mL each₹95
Set of standardized test chemical solutions in dropper bottles.
Specifications- Solutions
- 0.1M HCl, 0.1M CH3COOH, Lemon juice, Distilled H2O, 0.1M NaHCO3, 0.1M NaOH
- Volume
- 50 mL each
- Purity
- Analytical Reagent grade
- Clean porcelain spot plate / series of test tubes setWhat is it?Clean porcelain spot plate / series of test tubes set₹140
White glazed ceramic 12-cavity spot plate for clear color comparison.
Specifications- Cavities
- 12 hemispherical depressions (1 mL capacity each)
- Material
- Glazed chemical porcelain, acid/alkali resistant
- Dimensions
- 115 mm × 90 mm × 12 mm
- Glass dropper pipettesWhat is it?Glass dropper pipettes₹185
Standard laboratory apparatus used in pH Determination of Common Solutions using Universal Indicator.
Specifications- Category
- Chemistry Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Digital Pocket pH Pen Meter with calibration buffer packetsWhat is it?Digital Pocket pH Pen Meter with calibration buffer packets₹230
Standard laboratory apparatus used in pH Determination of Common Solutions using Universal Indicator.
Specifications- Category
- Chemistry Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
Tick items as you collect them. Tap + to see the product, specifications and buy options.
Stay safe
- Use a separate clean dropper for each solution to prevent cross-contamination.
- Do not touch active indicator paper test zones with fingers.
- Read the color immediately within 10-15 seconds before drying alters the hue.
- Rinse pH meter glass electrode thoroughly with distilled water and blot dry with lint-free tissue between tests.
Steps
- 1Place clean porcelain spot plate on a clean white surface.Observation
Place 6 clean dry porcelain cavity tiles on workbench; arrange solutions in order of expected acidity.
SafetyWear lab coat and splash-proof safety goggles.
- 2Tear small 1 cm strips of broad-range universal pH paper and place one strip in each well.Observation
Use clean dry glass rod to touch 0.1 M HCl to universal pH strip: color turns immediate scarlet red (pH 1.0).
SafetyRinse glass rod thoroughly in distilled water and dry with tissue between every sample.
- 3Using a clean dropper, apply 1 drop of dilute HCl onto the first strip and observe the instantaneous color change.Observation
Test fresh lemon juice: strip turns vibrant pinkish-red matching pH 2.5 on standard comparison chart.
SafetyDo not contaminate stock reagent bottles with sampling droppers.
- 4Compare the developed red color immediately with the standard pH reference chart to read pH ≈ 1.Observation
Test distilled water: strip turns pure forest green, confirming neutral pH 7.0.
SafetyEnsure wash bottle water is freshly distilled; atmospheric CO2 absorption can lower water pH to 5.8.
- 5Repeat the test with lemon juice (reddish orange, pH ~2), vinegar (orange, pH ~3), distilled water (green, pH ~7), baking soda (blue-green, pH ~8.5), and dilute NaOH (deep violet, pH ~13).Observation
Test sodium bicarbonate solution: turns distinct blue-green matching pH 8.5.
SafetyKeep basic solutions away from eyes.
- 6Cross-check readings using the digital pH electrode rinsed with distilled water between samples.Observation
Test 0.1 M NaOH: instant deep violet purple coloration confirms extreme alkalinity pH 13.0.
SafetyIn case of NaOH skin contact, wash immediately under copious flowing tap water for 15 minutes.
- 7Tabulate solution name, observed color, inferred pH, and acidic/basic nature.
Tap + on a step to see what you will observe and any safety tips.
Record your observations
| Test Solution Sample | Color with Universal Indicator | Observed pH (Indicator Paper) | Digital pH Meter Reading | Nature of Solution |
|---|---|---|---|---|
| 0.1 M Hydrochloric Acid (HCl) | Deep Scarlet Red | pH 1.0 | pH 1.02 | Strongly Acidic |
| Lemon Juice (Citric acid) | Pinkish Red | pH 2.5 | pH 2.35 | Moderately Acidic |
| Vinegar (Acetic acid, CH3COOH) | Orange | pH 3.0 | pH 2.88 | Weakly Acidic |
| Distilled Pure Water (H2O) | Neutral Green | pH 7.0 | pH 6.95 | Neutral |
| Sodium Bicarbonate (NaHCO3) | Blue-Green | pH 8.5 | pH 8.40 | Weakly Alkaline |
| 0.1 M Sodium Hydroxide (NaOH) | Deep Indigo Violet | pH 13.0 | pH 12.98 | Strongly Alkaline |
Tap a highlighted cell to write your own observation.
Result and conclusion
Constructed the standard color-coded pH scale (1 to 14). Identified lemon juice as pH 2.2 (strongly acidic), distilled water as pH 7.0 (neutral), and NaOH as pH 13.5 (strongly basic).
| Observation | What it means |
|---|---|
| Full Spectrum pH Correlation | Color transitions follow standard rainbow progression: Red (pH 1-3) -> Orange (pH 4-5) -> Green (pH 7) -> Blue (pH 9-10) -> Violet (pH >12). |
| Strong vs Weak Acid Contrast | HCl (0.1M) dissociates completely giving pH ~1.0; 0.1M Acetic acid dissociates only partially (~1.3%) giving pH ~2.9. |
| Buffer Stability in Salts | Baking soda (NaHCO3) hydrolyzes weakly in water generating bicarbonate buffer at pH ~8.4. |
| Digital Meter Verification | Visual color scale matched digital glass electrode measurements within ±0.15 pH units across the entire 1-13 spectrum. |
Sample readings. Replace with your own results.