REACTION OF BASES WITH METALS:

Metals like zinc, tin and aluminum react with strong alkalies like NaOH (caustic soda), KOH (caustic potash) to evolve hydrogen gas.

Zn(s) + 2NaOH(aq) Na₂ZnO₂ (aq) + H₂ (g)

Sodium zincate

Sn(s) + 2NaOH(aq) Na₂SnO₂ (aq) + H₂ (g)

Sodium stannite

2AI(s) + 2NaOH + 2H₂O 2NaAIO₂ (aq) + 3H₂ (g)

Sodium meta aluminate

Experiment: Take 2-3 pieces of zinc granules in a test tube and add about 2-3 ml of conc. NaOH solution in to it and warm the contents.

Observation: There is evolution of gas which burns with a pop sound (on bringing a burning candle near the mouth of tube).

The reaction involved is:

zinc sodium hydroxide sodium zincate hydrogen

(a metal) (conc.) (a salt) gas

Figure-Study of the reaction of sodium hydroxide with Zn metal

REACTION OF BASES WITH ACIDS (NEUTRALIZATION REACTION)

When a base reacts with an acid then salt and water are formed

i.e. Base + Acid → Salt + Water

This reaction is called neutralization reaction, because when base and acid react with each other, they neutralize each other’s effect (i.e. acid destroys the basic property of a base and a base destroys the acidic property of an acid)

(i)

sodium hydroxide hydrochloric acid sodium chloride water

(base) (acid) (salt)

(ii)

sodium hydroxide sulphuric acid sodium sulphate water

(base) (acid) (salt)

Conclusion: Reaction of a base with an acid is a neutralization of an acid by base

REACTION OF BASE WITH NON-METAL OXIDE:

Bases react with non-metal oxide to form salt and water

i.e. Non-metal oxide + Base Salt + water

This reaction is similar to the neutralization reaction between acid and base to form salt and water. Thus, the reaction between bases and non-metal oxides is a kind of neutralization reaction and shows that non-metal oxides are acidic oxides.

⇒ Reaction of calcium hydroxide (lime water) with carbon dioxide.

Calcium hydroxide (lime water) is a base and carbon dioxide is a non-metal oxide, so when they react with each other, salt and water are produced according to the reaction:

calcium hydroxide carbondioxide calcium water

(lime water) (non-metal oxide) carbonate

(base) (salt)

2NaOH(aq) + CO₂ (g) Na₃CO₃ (aq) + H₂O

Ca(OH)₂ (s) + SO₂ (g) CaSO₃ (aq) + H₂O

Conclusion: Reactions of bases with non-metal oxides are neutralization reactions which show the acidic nature of non-metal oxide.