Key Features of Strong vs. Weak Acids and Bases

What Are Acids and Bases?

Acids and bases are types of chemicals that behave differently in water.

• Acids give away protons, which are tiny particles called $H^+$ ions.
• Bases accept protons or give away particles called hydroxide ions ($OH^–$).

How strong an acid or base is depends on how well it breaks apart in water.

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Strong Acids:

1. Breakdown in Water: Strong acids break apart completely in water. This means most of the acid particles change into ions. For example, hydrochloric acid ($HCl$) and sulfuric acid ($H_2SO_4$) are strong acids.

2. pH Levels: Strong acids usually have a pH level less than 3. For instance, a solution of $HCl$ at 0.1 M has a pH of 1.

3. No Equilibrium: Strong acids don’t create a balance between the acid and its ions in water. Almost all the acid is just ions.

4. Common Strong Acids: Other strong acids include nitric acid ($HNO_3$), hydrobromic acid ($HBr$), and perchloric acid ($HClO_4$).

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Weak Acids:

1. Breakdown in Water: Weak acids only partly break apart in water. For example, acetic acid ($CH_3COOH$) does not fully change into ions. Some of it stays whole.

2. pH Levels: Weak acids usually have a pH greater than 3, depending on how strong they are. A 0.1 M solution of acetic acid has a pH of about 2.9.

3. Establishing Equilibrium: Weak acids create a balance between the acid that hasn’t broken apart and the ions. For instance, acetic acid can be shown like this:
   $CH_3COOH \rightleftharpoons H^+ + CH_3COO^-$

4. Common Weak Acids: Other examples include formic acid ($HCOOH$) and citric acid.

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Strong Bases:

1. Breakdown in Water: Strong bases, like sodium hydroxide ($NaOH$), break apart completely in water to make lots of hydroxide ions.

2. pH Levels: Strong bases usually have a pH greater than 11. For example, a 0.1 M solution of sodium hydroxide has a pH of about 13.

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Weak Bases:

1. Breakdown in Water: Weak bases, such as ammonia ($NH_3$), do not fully break apart, so they have fewer $OH^–$ ions in the solution.

2. pH Levels: The pH level for weak bases usually ranges from 7.5 to 10, depending on how strong they are.

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Knowing these characteristics helps us understand how acids and bases behave in chemical reactions.