Acids, Bases and Salts!
Acids:
Substances which release hydrogen ions as the only positive ions in aqueous solutions are called Acids.
Alkalis:
Substances which release hydroxide ions as the only negative ions in aqueous solutions are called Alkalis.
Bases:
Alkalis which are insoluble in water are called bases.
Physical properties of Acids:
Acids have a sour taste They turn blue litmus paper blue They turn Phenolphthalein to colorless.
They turn methyl orange to red.
Most acids are colorless.
Mineral acids can corrode metal, fabric and even skin!
Chemical properties of Acids:
Acids react with metals, above hydrogen in the reactivity series, to form salt and release hydrogen.
HCl (aq) + Ca (s) = CaCl2 (s) + H2 (g)
Acids react with bases/alkalis to form salt and water only. This reaction is known as neutralization reaction.
HNO3 (aq) + NaOH (aq) = NaNO3 (s) + H2O (l)
Acids react with metal carbonates to form a salt, water and carbon dioxide only.
HCl (aq) + CaCO3 (s) = CaCl2 (s) + H2O (l) + CO2 (g)
Physical Properties of Bases:
Most of the bases are colored.
Most of the bases are insoluble in water.
Soluble Bases are known as alkalis.
Physical Properties of Alkalis:
Alkalis have a bitter taste.
They have a soapy touch.
Alkalis can dissolve proteins therefore touching alkalis is unsafe as our skin is made up of proteins.
Alkalis turn red litmus paper blue.
Alkalis turn methyl orange yellow.
Alkalis turn phenolphthalein to pink.
Chemical properties of Alkalis/ bases:
Alkali reacts with ammonia salt on warning to produce salt, water and ammonia.
NaOH (aq) + (NH4)2SO4 (s) = Na2SO4 (s) + H2O (l) + NH3 (g)
Alkalis/Bases react with Acids to form salt and water only. This reaction is known as neutralization reaction.
KOH (aq) + HCl (aq) = KCl (s) + H2O (l)
Strong acids:
Acids which ionize to a large extent in dilute aqueous solution and release hydrogen ions in a large number are called strong acids.
Weak acids:
Acids which ionize poorly in aqueous solution and release hydrogen ions in small number, are called weak acids.
Strong alkalis:
Alkalis which ionize to a large extent in dilute aqueous solution and release hydroxide ions in a large number are called strong alkalis.
Weak alkalis:
Alkalis which ionize poorly in dilute aqueous solution and release hydroxide ions in a small number are called weak alkalis.
Neutralization reaction:
The reaction between acids and bases/alkalis to form salt and water only.
pH indicator:
It is a mixture of several indicators. It is used as a solution or in the form of indicator paper. It gives a number of color changes from red to purple when treated with acid or an alkali. When the color change takes place it is compared with the scale and pH of the solution is determined.
pH meter:
It is an electronic device which consists of a probe (sensor) and a display. The is placed in the solut...
