BASES / ALKALI PROPERTIES
A) Alkalis bitter in taste and have soap touch, i.e., a slippery sensation produces.
B) Turns red litmus blue, phenolphthalein solution pink, methyl orange yellow and turmeric Powder brown.
C) Bases conduct electricity in solution.
D) Action of acid: When a base reacts with acid salt and water are formed this is called as neutralisation.
\(
2NaOH + H_2 SO_4 \xrightarrow{{}}Na_2 SO_4 + 2H_2 O
\)
\(
2Al(OH)_3 + 3H_2 SO_4 \xrightarrow{{}}Al_2 (SO_4 )_3 + 6H_2 O
\)
\(
NH_4 OH + HCl\xrightarrow{{}}NH_4 Cl + H_2 O
\)
5)Action with non-metal oxides:Bases react with non-metal oxides to form salt and water.
\(
Ca(OH)_2 + CO_2 \xrightarrow{{}}CaCO_3 + H_2 O
\)
\(
KOH + CO_2 \xrightarrow{{}}K_2 CO_3 + H_2 O
\)
\(
2NaOH + CO_2 \xrightarrow{{}}Na_2 CO_3 + H_2 O
\)
6)Action with ammonium salt:
When alkalis are warmed with ammonium salts, they liberated ammonia gas
\(
2NH_4 Cl + Ca(OH)_2 \xrightarrow{{}}CaCl_2 + 2H_2 O + 2NH_{3(g)}
\)
\(
(NH_4 )_2 SO_4 + 2NaOH\xrightarrow{{}}Na_2 SO_4 + 2H_2 O + 2NH_{3(g)}
\)
7)Action of heat:All bases (except NaOH and KOH) decompose on heating to form their oxides and water.
\(
Ca(OH)_2 \xrightarrow{{heat}}CaO + H_2 O
\) \(
2Al(OH)_3 \xrightarrow{{heat}}Al_2 O_3 + 3H_2 O
\)
Uses:
i) Sodium hydroxide is used in the manufacture of soap, paper and a synthetic fibre called ‘rayon’.
ii) Calcium hydroxide (slaked lime) is used in the manufacture of bleaching powder.
iii) Magnesium hydroxide is used an ‘antacid’ to neutralise excess acid in the stomach and cure indigestion.
iv) Sodium carbonate is used as washing soda and for softening hard water.
v) Sodium hydrogen carbonate is used as baking soda in cooking food, for makiing.