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Chemistry - Acids, Bases and Salts

Grade 10ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Acids are substances that dissociate in aqueous solution to produce hydronium ions (H3O+H_3O^+) as the only positively charged ions. For example: HCl+H2OightarrowH3O++Cl−HCl + H_2O ightarrow H_3O^+ + Cl^-.

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Bases are oxides or hydroxides of metals that react with hydronium ions of an acid to form salt and water only. Alkalis are bases soluble in water, producing hydroxyl ions (OH−OH^-).

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The basicity of an acid is the number of hydronium ions (H3O+H_3O^+) produced by the ionization of one molecule of the acid in aqueous solution. For example, H2SO4H_2SO_4 is dibasic.

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The acidity of a base is the number of hydroxyl ions (OH−OH^-) produced by the ionization of one molecule of the base in aqueous solution. For example, Ca(OH)2Ca(OH)_2 is diacidic.

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Neutralization is the process where H+H^+ ions from an acid react with OH−OH^- ions from a base to form water (H2OH_2O), accompanied by the formation of a salt.

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pH Scale: A scale ranging from 00 to 1414 used to measure the acidity or alkalinity of a solution. pH<7pH < 7 is acidic, pH=7pH = 7 is neutral, and pH>7pH > 7 is alkaline.

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Normal Salts are formed by the complete replacement of ionizable hydrogen atoms of an acid by a metal or ammonium ion, e.g., Na2SO4Na_2SO_4.

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Acid Salts are formed by the partial replacement of ionizable hydrogen atoms of a polybasic acid by a metal or ammonium ion, e.g., NaHSO4NaHSO_4.

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Basic Salts are formed by the partial replacement of hydroxyl groups of a polyacidic base by an acid radical, e.g., Pb(OH)ClPb(OH)Cl.

📐Formulae

pH=−log⁡10[H+]pH = -\log_{10}[H^+]

H++H2O→H3O+H^+ + H_2O \rightarrow H_3O^+

Acid+Base→Salt+WaterAcid + Base \rightarrow Salt + Water

Acid+Carbonate→Salt+Water+CO2↑Acid + Carbonate \rightarrow Salt + Water + CO_2 \uparrow

Acid+Active Metal→Salt+H2↑Acid + Active\ Metal \rightarrow Salt + H_2 \uparrow

NaOH+HCl→NaCl+H2ONaOH + HCl \rightarrow NaCl + H_2O

💡Examples

Problem 1:

Write the balanced chemical equation for the reaction between dilute sulphuric acid (H2SO4H_2SO_4) and Sodium Carbonate (Na2CO3Na_2CO_3).

Solution:

Na2CO3+H2SO4→Na2SO4+H2O+CO2↑Na_2CO_3 + H_2SO_4 \rightarrow Na_2SO_4 + H_2O + CO_2 \uparrow

Explanation:

When a dilute acid reacts with a metal carbonate, it produces the corresponding salt, water, and carbon dioxide gas.

Problem 2:

Classify NaHSO4NaHSO_4 as a salt and explain why it shows acidic properties in solution.

Solution:

NaHSO4NaHSO_4 is an Acid Salt. In aqueous solution, it ionizes: NaHSO4→Na++H++SO42−NaHSO_4 \rightarrow Na^+ + H^+ + SO_4^{2-}.

Explanation:

Because it contains a replaceable hydrogen atom, the H+H^+ ion released in water gives the solution acidic properties, such as turning blue litmus red.

Problem 3:

Calculate the basicity of Orthophosphoric acid (H3PO4H_3PO_4).

Solution:

The basicity is 33 (Tribasic).

Explanation:

One molecule of H3PO4H_3PO_4 contains three ionizable hydrogen atoms: H3PO4⇌3H++PO43−H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-}.