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Properties of Bases

Properties of Bases

The name base has long been associated with a class of compounds whose aqueous solutions are characterized by:
  • a bitter taste;
  • a “soapy” feeling when applied to the skin;
  • ability to restore the original blue color of litmus that has been turned red by acids;
  • ability to react with acids to form salts.
The word “alkali” is synonymous with the term 'base'. The root word comes from the Latin word kalium meaning potash, which is the origin of the name for potassium. Wood ashes were the traditional source of the strong base KOH used for cleaning and for the manufacture of soap since ancient times. Sodium Hydroxide or Lye is a common household cleaning agent, often found in oven cleaners or bathroom grime removers; it works equivalently to KOH.

Other common examples of a bases include: ammonia a strong smelling cleaning solution and lime, not the lime fruit, but rather the white powder which is used to make concrete or which can be mixed with water to create whitewash, an economical substitute for white paint.

Just as an acid is a substance that liberates hydrogen ions into solution, a base yields hydroxide ions when dissolved in water:

NaOH(s) → Na+ (aq) + OH (aq)

Neutralization of Acids

An important feature of bases is that they are the functional opposite of acids. Acids and bases can both be corrosive but when added together in the correct proportions each cancels out the corrosive effect of the other.

For example when the base sodium hydroxide is dissolved in water it decomposes into hydroxide and sodium ions:

NaOH → Na+(aq) + OH-(aq)

and similarly, hydrogen chloride disolves in water to form hydrogen and chloride ions:

HCl + H2O → H2O+ + Cl-(aq) + H+(aq)

When the two solutions are mixed, the H+ and OH− ions combine to form water molecules:

H+(aq) + OH-(aq) → 2 H2O

If equal quantities of NaOH and HCl are dissolved, the base and the acid exactly neutralize, leaving only NaCl, i.e. common table salt, in solution.

Weak bases can be used to neutralize acid spills, for example baking soda or egg white. Note that attempting to neutralize an acid spill with a strong base, such as lye or ammonia, can cause a violent reaction, and the base itself may cause just as much damage as the original acid spill.

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