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Helpful Hint!

Although the other halogens make strong acids, hydrofluoric acid (HF) is a weak acid. Despite being weak, it is incredibly corrosive—hydrofluoric acid dissolves glass and metal!

Most acids and bases are weak. You should be familiar with the most common strong acids and assume that any other acids are weak.

Formula	Strong Acid

HClO₄	Perchloric acid
HNO₃	Nitric acid

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H₂SO₄

Sulfuric acid

HCl, HBr, HI Hydrohalic acids

Within a series of oxyacids, the ions with the greatest number of oxygen molecules are the strongest. For example, nitric acid (HNO₃) is strong, but nitrous acid (HNO₂) is weak. Perchloric acid (HClO₄ ) is stronger than chloric acid (HClO₃), which is stronger than the weak chlorous acid (HClO₂). Hypochlorous acid (HClO) is the weakest of the four.

Common strong bases are the hydroxides of Group 1 and most Group 2 metals. For example, potassium hydroxide and calcium hydroxide are some of the strongest bases. You can assume that any other bases (including ammonia and ammonium hydroxide) are weak.

		Formula	Strong Base

		LiOH	Lithium hydroxide

		NaOH	Sodium hydroxide

		KOH	Potassium hydroxide

		RbOH	Rubidium hydroxide

		CsOH	Cesium hydroxide

		Ca(OH)₂	Calcium hydroxide
		Sr(OH)₂	Strontium hydroxide
		Ba(OH)₂	Barium hydroxide

Acids and bases that are strong are not necessarily concentrated, and weak acids/bases are not necessarily dilute. Concentration has nothing to do with the ability of a substance to dissociate. Furthermore, polyprotic acids are not necessarily stronger than monoprotic acids.

Properties of Acids and Bases

Now that you are aware of the acid-base theories, you can learn about the physical and chemical properties of acids and bases. Acids and bases have very different properties, allowing them to be distinguished by observation.

Indicators

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