• Skip to main content
  • Skip to secondary menu
  • Skip to primary sidebar
  • Skip to footer
  • ICSE Solutions
    • ICSE Solutions for Class 10
    • ICSE Solutions for Class 9
    • ICSE Solutions for Class 8
    • ICSE Solutions for Class 7
    • ICSE Solutions for Class 6
  • Selina Solutions
  • ML Aggarwal Solutions
  • ISC & ICSE Papers
    • ICSE Previous Year Question Papers Class 10
    • ISC Previous Year Question Papers
    • ICSE Specimen Paper 2021-2022 Class 10 Solved
    • ICSE Specimen Papers 2020 for Class 9
    • ISC Specimen Papers 2020 for Class 12
    • ISC Specimen Papers 2020 for Class 11
    • ICSE Time Table 2020 Class 10
    • ISC Time Table 2020 Class 12
  • Maths
    • Merit Batch

A Plus Topper

Improve your Grades

  • CBSE Sample Papers
  • HSSLive
    • HSSLive Plus Two
    • HSSLive Plus One
    • Kerala SSLC
  • Exams
  • NCERT Solutions for Class 10 Maths
  • NIOS
  • Chemistry
  • Physics
  • ICSE Books

How can we measure the strength of acids and alkalis?

November 19, 2022 by Veerendra

How can we measure the strength of acids and alkalis?

    1. An acid produces hydrogen ions in aqueous solution. The acidity of a solution is a measure of the concentration of the hydrogen ions in the solution.
  1. A base produces hydroxide ions in aqueous solution. The alkalinity of a solution is a measure of the concentration of the hydroxide ions in the solution.
  2. In 1909, Soren Sorensen proposed the pH scale for measuring acidity or alkalinity of an aqueous solution.

The pH scale

How can we measure the strength of acids and alkalis 1

  1. The pH scale normally has a range of values from 0 to 14 to indicate how acidic or alkaline an aqueous solution is.
  2. The pH value measures the concentration of hydrogen ions or hydroxide ions.
    pH < 7 → acidi solution
    pH = 7 → neutral solution
    pH > 7 → alkaline solution
  3. The lower the pH value, the higher the concentration of hydrogen ions.
    The higher the pH value, the higher the concentration of hydroxide ions.
  4. The pH of values some common solutions used in daily life are shown below.
    How can we measure the strength of acids and alkalis 2
  5. The pH value of an aqueous solution can be measured by using
    (a) Universal Indicator
    (b) pH meter
    (c) acid-base indicators
    How can we measure the strength of acids and alkalis 3

Table shows examples of acid-base indicators.

IndicatorpH rangeColour change
Acid         NeutralAlkali
Methyl orange3.0 – 5.0RedOrangeYellow
Bromothymol blue6.0 – 8.0YellowGreenBlue
Phenolphthalein8.0-10.0ColourlessColourlessPink

People also ask

  • What is the definition of an acid and a base?
  • What is the definition of an acid in chemistry?
  • What is the definition of a base in chemistry?
  • Classification of Acids
  • Preparation of Acids
  • What are the chemical properties of an acid?
  • General Properties of Acids
  • Uses of Acids
  • Preparation of Bases
  • General Properties of Bases
  • What determines a Strong Base and a Weak Base
  • What are the uses of Bases
  • How to calculate concentration of acids and alkalis?
  • How do you prepare a standard solution?
  • What is meant by a neutralization reaction?
  • How does titration determine concentration?
  • Relationship between pH values and molarity of acids and alkalis
  • Concept of the pH Scale
  • Role of pH in everyday life
  • What is the pH of a salt solution

Strong and weak acids

  • The strength of an acid or alkali depends on the degree of dissociation of the acid or alkali in water.
  • The degree of dissociation measures the percentage of acid molecules that ionise when dissolved in water.
  • A strong acid is an acid which ionises or dissociates completely in water to produce a high concentration of hydrogen ions.
  • Hydrochloric acid is a strong acid. It is 100% ionised in water. All the hydrogen chloride molecules that dissolve in the water ionise completely into hydrogen ions and chloride ions.
    How can we measure the strength of acids and alkalis 4
  • A weak acid is an acid which ionises partially in water to produce a low concentration of hydrogen ions.
  • Ethanoic acid is a weak acid. Dilute ethanoic acid is about 0.4% ionised, only 4 out of every 1000 ethanoic acid molecules ionise. As fast as the acid molecules ionise to produce ions, the ions combine back again to give the original acid molecules in a reversible reaction.
    How can we measure the strength of acids and alkalis 5
    How can we measure the strength of acids and alkalis 6
  • Examples of strong and weak acids are shown in Table.
    AcidNameParticles
    Strong acidHydrochloric acid, HClH+, Cl–
    Nitric acid, HNO3H+, NO3–
    Sulphuric acid, H2S04H+, HSO4–, SO42-
    Weak acidCarbonic acid, H2C03H+, HCO3–, CO32-, H2CO3
    Ethanoic acid, CH3COOHH+, CH3COO–, CH3COOH
    Sulphurous acid, H2SO3H+, HSO3–, SO32-, H2SO3
  • Strong acid and weak acid are defined as follows.
    A strong acid is completely ionised in water to produce a high concentration of hydrogen ions.
    A weak acid is partially ionised in water to produce a low concentration of hydrogen ions.
  • The pH of an acid solution changes with concentration of the acid. The concentration of the acid affects the concentration of hydrogen ions produced. For example:
    10 mol dm-3 hydrochloric acid: pH = 1
    01 mol dm-3 hydrochloric acid: pH = 2
  • pH values can be used to compare the acid strength of different acids. All the acids to be compared must be of the same concentration.
    For example:
    10 mol dm-3hydrochloric acid: pH = 1
    10 mol dm-3 ethanoic acid: pH = 3
  • For two different acids of the same concentration, the acid with the lower pH value is the stronger acid, i.e. higher degree of ionisation in water.

Strong and weak alkalis

  • Sodium hydroxide is a strong alkali. It ionises fully when dissolved in water.
    How can we measure the strength of acids and alkalis 7
  • A strong alkali is an alkali which is fully ionised in water to produce a high concentration of hydroxide ions.
  • A weak alkali is an alkali which ionises partially in water to produce a low concentration of hydroxide ions.
  • Ammonia is an example of a weak alkali. It is only partly ionised in water, which means the ionisation of ammonia in water is incomplete. Only a small amount of ammonia molecules are ionised in water to produce ammonium ions and hydroxide ions.
    How can we measure the strength of acids and alkalis 8
  • Examples of strong and weak alkalis are shown in Table.
    AlkaliNameParticles
    Strong alkaliSodium hydroxide, NaOHNa+, OH–
    Potassium hydroxide, KOHK+, OH–
    Barium hydroxide, Ba(OH)2Ba2+, OH–
    Weak alkaliAmmonia, NH3NH3, NH4+, OH–
    Methylamine, CH3NH2CH3NH2, CH3NH3+, OH–
    Hydrazine, N2H4N2H4, N2H5+, OH–
  • Strong alkali and weak alkali are defined as follows.
    A strong alkali is completely ionised in water to produce a high concentration of hydroxide ions.
    A weak alkali is partially ionisesed in water to produce a low concentration of hydroxide ions.
  • The pH of an alkali solution changes with concentration of the alkali. The concentration of the alkali affects the concentration of hydroxide ions produced.
    For example:
    10 mol dm-3m-3 sodium hydroxide solution pH = 13
    01 mol dm-3 sodium hydroxide solution pH = 12
  • pH values can be used to compare the strength of different alkalis. All the alkalis to be compared must be of the same concentration. For example:
    10 mol dm-3 sodium hydroxide: pH = 13
    10 mol dm-3 ammonia solution: pH = 11
  • For two different alkalis of the same concentration, the alkali with the higher pH value is the stronger alkali, i.e. higher degree of ionisation in water.

 

Filed Under: Chemistry Tagged With: Acids, Acids and Alkalis, Alkalis, How can we measure the strength of acids and alkalis?, pH, pH Scale, Strong acids, Strong alkalis, Strong and weak acids, Strong and weak alkalis, The pH scale, The Strength of Acids, The Strength of Acids and Alkalis, weak acids, weak alkalis

Primary Sidebar

  • MCQ Questions
  • RS Aggarwal Solutions
  • RS Aggarwal Solutions Class 10
  • RS Aggarwal Solutions Class 9
  • RS Aggarwal Solutions Class 8
  • RS Aggarwal Solutions Class 7
  • RS Aggarwal Solutions Class 6
  • ICSE Solutions
  • Selina ICSE Solutions
  • Concise Mathematics Class 10 ICSE Solutions
  • Concise Physics Class 10 ICSE Solutions
  • Concise Chemistry Class 10 ICSE Solutions
  • Concise Biology Class 10 ICSE Solutions
  • Concise Mathematics Class 9 ICSE Solutions
  • Concise Physics Class 9 ICSE Solutions
  • Concise Chemistry Class 9 ICSE Solutions
  • Concise Biology Class 9 ICSE Solutions
  • ML Aggarwal Solutions
  • ML Aggarwal Class 10 Solutions
  • ML Aggarwal Class 9 Solutions
  • ML Aggarwal Class 8 Solutions
  • ML Aggarwal Class 7 Solutions
  • ML Aggarwal Class 6 Solutions
  • HSSLive Plus One
  • HSSLive Plus Two
  • Kerala SSLC

Recent Posts

  • ISC Computer Science Question Paper 2015 Solved for Class 12
  • The Happiest Day of My Life Essay | Essay on The Happiest Day of My Life for Students and Children in English
  • 4 Eagle Scout Letters of Recommendation | Examples, Format and How To Write?
  • Bru Dhatu Roop In Sanskrit – ब्रू (बोलना) धातु के रूप की परिभाषा, भेद और उदाहरण – (संस्कृत व्याकरण)
  • 10 Lines on Computer for Students and Children in English
  • Essay on Population | Population Essay for Students and Children in English
  • What is Matter and what are the Properties of a Solid, Liquid and Gas
  • Hindi Grammar – हिन्दी व्याकरण (Vyakaran)
  • 10 Lines on Mithali Raj for Students and Children in English
  • 10 Lines on Bhagat Singh for Students and Children in English
  • Essay on Reading is a Good Habit | Reading is a Good Habit Essay for Students and Children in English

Footer

  • RS Aggarwal Solutions
  • RS Aggarwal Solutions Class 10
  • RS Aggarwal Solutions Class 9
  • RS Aggarwal Solutions Class 8
  • RS Aggarwal Solutions Class 7
  • RS Aggarwal Solutions Class 6
  • Picture Dictionary
  • English Speech
  • ICSE Solutions
  • Selina ICSE Solutions
  • ML Aggarwal Solutions
  • HSSLive Plus One
  • HSSLive Plus Two
  • Kerala SSLC
  • Distance Education
DisclaimerPrivacy Policy
Area Volume Calculator