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CBSE Class 11 chemistry · ionic equilibrium and pH · Physical chemistry

Source: CBSE Class 11 chemistry practical syllabus · use your school laboratory manual (NCERT Lab Manual where your school uses it).

Determination of pH of solutions (Class 11 chemistry practical)

You compare the colour of pH paper and universal indicator with the chart your laboratory manual supplies.

Which solutions and their concentrations are listed in your manual — not invented here.

Published practice page. Concentrations, masses, and numerical answers come from your school laboratory manual and your own readings — not invented here. Not yet reviewed by a named chemistry reviewer. Version 1.0.0, updated 2026-10-03.

Safety — read before you start

Safety warning. Practise here. Perform the real experiment only in your school lab, with your teacher present.

  • Corrosive acids and bases in assigned set.
  • Do not touch indicator stains to skin.

Wear: Lab coat, Splash goggles, Gloves, as your teacher directs.

Follow your teacher’s disposal instructions. Do not pour leftovers down a household drain.

Loads only after you tap. Use the lab hands to pick up and use equipment (pointer hidden in the scene). Falls back to a flat diagram if WebGL is unavailable.

Aim

To determine the approximate pH of the solutions assigned in your laboratory manual using pH paper and universal indicator.

Methods and quantities can differ between schools. Follow your teacher's instructions.

Apparatus and chemicals

Apparatus and chemicals
ItemNote
pH paper (narrow range if provided)Dip briefly; match to chart.
Universal indicator paper or solutionFull range; compare to colour chart.
Glass rod or dropperDo not cross-contaminate samples.
Clean test tubes or spot plateOne tube per solution.
Chart from manualOfficial colour–pH correspondence.
Assigned solutions (acids, bases, salts) (test solutions)Use the concentration, mass, volume, and sample names printed in your school laboratory manual. This page does not invent numerical results for you.
Universal indicator (universal indicator)Use the form (paper or solution) your school provides.
Calorimeter cup with thermometer for acid–base mix
Note T₁ before mixing, then T₂ after. ΔT and ΔH come from your thermometer and your manual’s formula — not from this photo.

Theory and reaction

Open

pH = −log10[H+] for aqueous solutions (activity approximations as your syllabus treats).

pH paper is impregnated with indicators that change colour over a narrow range; universal indicator spans roughly pH 1–14.

Salts of strong acid + strong base are near neutral; strong acid low pH; strong base high pH; weak acids/bases and hydrolysed salts fall in between.

pH = -log10 [H+]; pOH = -log10 [OH-]; pH + pOH = 14 at 25 C.

Procedure

  1. Pour a small volume of each assigned solution into a labelled test tube.
  2. Dip a fresh strip of pH paper, remove immediately, and compare wet colour to the chart without soaking the paper.
  3. Add one drop of universal indicator (or use universal paper) to a fresh sample. Match the colour to the universal chart.
  4. Record approximate pH for each solution in your observation table.
  5. Rinse the rod between samples or use separate droppers.

Observation table

Enter the readings from your school lab in the practical file below. This page does not fill them in for you.

Type the readings in your practical file

Calculation

No titre. If your manual asks you to classify as acidic / basic / neutral, use your recorded pH estimates.

Result

Tabulate solution name and pH range you read from the charts. Leave blank for solutions not assigned.

Precautions

  • Do not leave pH paper in solution — indicator leaches and reading fades.
  • Avoid cross-contamination between acids and bases.
  • Wear goggles; some assigned solutions are corrosive.

Viva questions

Answer one question at a time. The full answers stay closed until you open them.

Question 1 of 4

pH is defined as…

Answer choices

Pick an answer first.

Show all questions and answers

  1. pH is defined as…

    Answer: −log₁₀ of hydrogen ion activity / concentration (as syllabus states). Reason: Standard school definition uses logarithm of [H⁺].

  2. Universal indicator is useful because…

    Answer: It shows a wide pH range via a colour spectrum. Reason: Broad range colour change across pH.

  3. A solution of NaCl from HCl + NaOH is expected to be…

    Answer: About neutral. Reason: Strong acid + strong base salt → near neutral aqueous solution.

  4. At 25 °C in water, pH + pOH equals…

    Answer: 14. Reason: Kw relationship in neutral water reference scale.

Common mistakes

  • Reading paper after it has dried to a different shade.
  • Using water-rinsed rod without drying between strong acid and strong base.
  • Writing a precise pH to two decimals when the chart only allows an approximate range.
  • Inventing pH values not matched to your strip colour.

Frequently asked questions

Can I do this at home?
No. Use this page to practise the order of steps and viva. Do the real experiment only in your school laboratory, with your teacher present.

Your practical file

Name, school, and roll number are optional and are not sent anywhere.

The practical file opens on this device.

Review

Not yet reviewed by a named chemistry reviewer. Published for practice only — follow your teacher and laboratory manual for quantities and safety.

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