7.1 Characteristic Properties of Acids and Bases
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1. Describe the characteristic chemical reactions of acids with metals.
Acids react with sufficiently reactive metals to produce a salt and hydrogen gas.
Example: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Example: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
2. Describe the characteristic chemical reactions of acids with bases.
Acids react with bases (metal oxides or hydroxides) in a neutralization reaction to form a salt and water only.
Example: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Example: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
3. Describe the characteristic chemical reactions of acids with carbonates.
Acids react with metal carbonates to form a salt, water, and carbon dioxide gas.
Example: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
Example: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
4. State the color updates for litmus, thymolphthalein, and methyl orange indicators in acidic solutions.
- Litmus: Red
- Thymolphthalein: Colorless
- Methyl orange: Red
5. State the color updates for litmus, thymolphthalein, and methyl orange indicators in alkaline solutions.
- Litmus: Blue
- Thymolphthalein: Blue
- Methyl orange: Yellow
6. How can you look up or state the relative acidity or alkalinity of an aqueous solution?
By looking up or identifying its numerical values on the pH scale using Universal Indicator paper or a digital pH probe.
7. What do the values on the pH scale tell us about a solution?
A pH value of 7 indicates a strictly neutral solution. Values below 7 denote increasing acidity (with lower numbers being strongly acidic), and values above 7 denote increasing alkalinity (with higher numbers being strongly alkaline).
8. Define acids and bases according to the proton transfer theory.
Acids function explicitly as proton (H+) donors, while bases function as proton (H+) acceptors.
9. What distinguishes a strong acid from a weak acid?
A strong acid ionizes completely in an aqueous solution, releasing all its hydrogen ions into the solution. A weak acid ionizes only partially in an aqueous solution, establishing a dynamic equilibrium.
10. Provide common laboratory examples of strong and weak acids.
Strong acids: Hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3).
Weak acids: Ethanoic acid (CH3COOH) and carbonic acid (H2CO3).
Weak acids: Ethanoic acid (CH3COOH) and carbonic acid (H2CO3).