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7.8: Acid–Base Reactions

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    Learning Objectives

    • Identify Acid-Base Neutralization reactions and their products.

    Neutralization Reactions

    Acids and bases react chemically with each other to form salts. A salt is a general chemical term for any ionic compound formed from an acid and a base. In reactions where the acid is a hydrogen-ion-containing compound and the base is a hydroxide-ion-containing compound, water is also a product. The general reaction is as follows:

    \[\text{acid + base} → \text{water + salt}\]

    The reaction of acid and base to make water and a salt is called neutralization. Like any chemical equation, a neutralization chemical equation must be properly balanced. For example, the neutralization reaction between sodium hydroxide and hydrochloric acid is as follows:

    \[\ce{NaOH (aq) + HCl (aq) \rightarrow NaCl (aq) + H_2O (ℓ)} \label{Eq2}\]

    with coefficients all understood to be one. The neutralization reaction between sodium hydroxide and sulfuric acid is as follows:

    \[\ce{2NaOH (aq) + H_2SO_4 (aq) \rightarrow Na_2SO_4(aq) + 2H_2O (ℓ)} \label{Eq3}\]

    Example \(\PageIndex{1}\): Neutralizing Nitric Acid

    Nitric acid (HNO3(aq)) can be neutralized by calcium hydroxide (Ca(OH)2(aq)). Write a balanced chemical equation for the reaction between these two compounds and identify the salt that it produces.

    Solution

    Steps Explanation Equation

    Write the unbalanced equation.

    This is a double displacement reaction, so the cations and anions swap to create new products.

    Ca(OH)2(aq) + HNO3(aq) → Ca(NO3)2(aq) + H2O(ℓ)
    Balance the equation.

    Because there are two OH− ions in the formula for Ca(OH)2, we need two moles of HNO3 to provide H+ ions

    Ca(OH)2(aq) + 2HNO3(aq) → Ca(NO3)2(aq) + 2H2O(ℓ)
    Additional step: identify the salt.   The salt formed is calcium nitrate.

    Exercise \(\PageIndex{1}\)

    Hydrocyanic acid (\(\ce{HCN(aq)}\)) can be neutralized by potassium hydroxide (\(\ce{KOH(aq)}\)). Write a balanced chemical equation for the reaction between these two compounds and identify the salt that it produces.

    Answer

    \[\ce{KOH (aq) + HCN(aq) → KCN (aq) + H2O(ℓ)} \nonumber\]

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