An acid is a substance that produces hydrogen ions, in aqueous solution.
Some of the common acids, their formulae and the ions they produce in aqueous solution are listed below:-
Acids | Formulae | Ions produced in aqueous solution:- | Ions produced in aqueous solution:- |
Ethanoic acid | CH3COOH | H+ (aq) | CH3COO- |
Hydrochloric acid | HCL | H+ (aq) | Cl- |
Nitric acid | HNO3 | H+ (aq) | NO3- |
Sulfuric acid | H2SO4 | H+ (aq) | SO4 (-2) |
For example:-
hydrochloric acid------ hydrogen ion + chloride ion
HCl (aq) -------- H+ (aq) + Cl- (aq)
sulfuric acid------- hydrogen ion + sulfate ion
2-
H2SO4 (aq)------- 2H+ (aq) + SO4 (aq)
The hydrogen ions produced are responsible for the properties of the acids.
Properties of Acids:-
Acids have a sour taste.
Acids are corrosive.
Acids have a rough texture.
Acids turn blue litmus paper to red.
Acids react with reactive metals to form salt and hydrogen gas. (reactivity series)
metal + acid -------- salt + hydrogen
magnesium + hydrochloric acid -------- magnesium chloride + hydrogen
Mg (s) + 2HCl (aq) -------- MgCl2 (aq) + H2 (g)
Magnesium Chloride in the above reaction is a salt. Salts produced from hydrochloric acid are called chlorine, those produced from sulfuric acid are called sulfates, those produced from citric acid are called citrates and those produced from nitric acid are called nitrates.
In order to check the production of hydrogen or carbon dioxide gas visit.
Not all metals react with acids, some are too unreactive to do so. For instance lead, copper and silver are unable to react. When lead reacts with hydrochloric acid, it produces a layer of lead (II) chloride around the metal. This layer is insoluble in water and prevents further attacks on the metal.
6. Acids will react with carbonates and hydrogen carbonates to produce salt, water and carbon dioxide gas.
carbonate + acid --------- salt + water + carbon dioxide gas
Sodium carbonate + sulfuric acid --------- sodium sulfate + water + carbon dioxide gas
Na2CO3 + H2SO4 (aq) ---------- Na2SO4 (aq) + H2O (l) + CO2 (g)
7. Acids react with metal oxides and hydroxides to form water and salt.
metal oxide + acid ------- water + salt
Zinc oxide + Hydrochloric acid --------- Zinc chloride + water
ZnO (s) + 2HCl (aq) --------- ZnCl2 (s) + H2O (l)
What is the role of water in acids?
Acids only display their properties when they are dissolved in water. This is because acids produce hydrogen ions only when they are dissolved in water. It is the hydrogen ions that give the acids its properties. That is why no reaction will take place between acid dissolved in organic solvent and any metal.
Uses of Acids:-
The most commonly used acid is sulfuric acid. The most important uses of sulfuric acid is listed below:-
Dilute sulfuric acid is used in car batteries. It reacts with lead plates and lead (IV) plates in the battery to generate electrical energy which is used to run the car engine.
Concentrated sulfuric acid is used in the manufacture of detergents to convert hydrocarbons to organic acids. Which is then reacted with sodium hydroxide to produce detergents.
It is also used for the manufacture of fertilizers. It is the starting material for the production of ammonium sulfate and superphosphate, the active ingredients in fertilizers.
Other Acids:-
Hydrochloric acid: It is used to clear impurities such as rust and scale from metal and aluminum alloys.
Ethanoic acid: It is used in vinegar to act as food preservative and flavor enhancer.
Phosphorus acid: It is used in food and beverages to give them a sour taste.
In the next lesson, we will go through alkalis.
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