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PROPERTIES OF LOWRY–BRØNSTED ACIDS AND BASES 245

Table 6.3 Typical properties of Lowry–Brønsted bases

Base property Example from everyday life
Bases react with an acid to form a salt and Rubbing a dock leaf (which contains an
water (‘neutralization’) organic base) on the site of a nettle sting
(which contains acid) will neutralize the
acid and relieve the pain
Bases react with esters to form an alcohol Aqueous solutions of base feel ‘soapy’ to the
and carboxylic acid (‘saponification’) touch
Bases can be corrosive Oven cleaner comprising caustic soda
(NaOH) can cause severe burns to the skin

pools of stagnant rainwater collect. Although calcium carbonate is essentially insoluble
in water, minute amounts do dissolve to form a dilute solution, which is alkaline.
The alkali in these water pools reacts with organic matter such as algae and moss
growing on the stone. The most common of these reactions is saponification (see
p. 240), which causes naturally occurring esters to split, to form the respective car-
boxylic acid and an alcohol. Once formed, this carboxylic acid
reacts with more alkaline rainwater to form a metal carboxylate,
according to
Metal carboxylates are
2+ − called soaps because
2RCOOH (aq) + CaCO 3(aq) −−→ Ca (RCOO ) 2(aq)
they saponify oils in
+ CO 2(aq) + H 2 O (6.19) the skin and decrease
the surface tension γ of
The carbon dioxide generated by Equation (6.19) generally remains water, which makes the
in solution as carbonic acid, although the rainwater can look a little surfaces more slippery.
cloudy because minute bubbles form.
Like most other metal carboxylates, the calcium carboxylate
(Ca(RCOO) ) formed during Equation (6.19) readily forms a
2
‘soap’, the name arising since its aqueous solutions feel slippery The serial TV programs
and soapy to the touch. The other commonly encountered metal known as ‘soap operas’
carboxylates are the major components of household soap, which earned their name in
is typically a mixture of potassium stearate and potassium palmitate the USA at a time when
much of a program-
(the salts of stearic and palmitic acids).
maker’s funding came
In summary, steps of limestone become slippery because the
from adverts for house-
stagnant water on their surface is alkaline, thereby generating a
hold soap.
solution of an organic soap. Other typical properties of bases and
alkalis are listed in Table 6.3.

Why is the acid in a car battery more corrosive
than vinegar?

pH

−3
Car batteries generally contain sulphuric acid at a concentration of about 10 mol dm .
It is extremely corrosive, and can generate horrific chemical burns. By contrast, the