Page 24 - Curriculum Visions Dynamic Book

Sulphuric acid
Sulphuric acid, a colourless, thick, heavy and “oily” liquid is a mineral acid that will react with compounds of most metals. Sulphuric acid is used widely in industry, for example, in the making of fertilisers (superphosphates), paints, synthetic fibres, detergents, dyes, and explosives.
Hot, concentrated sulphuric acid is an oxidising agent. It will react with many materials, even attacking less reactive metals such as copper, as demonstrated opposite.
Here we also use sulphuric acid to demonstrate the ability of acids to remove water from many compounds. For example, if a piece of sugar is placed in sulphuric acid, it becomes a black blob of carbon, all the water having been removed from the sugar molecules.
The effect of removing water is called dehydration. If sulphuric acid touches human skin, the molecules in the
skin immediately begin to lose their water. We call this an acid burn.
Acid burns are among the most serious accidents that can happen, especially if splashes should get into the eye.
 The acid is added to white sugar.
EQUATION: Dehydration of sucrose
Concentrated sulphuric acid dehydrates sugars
If concentrated sulphuric acid
is added to sugar, the sugar dehydrates, going black and losing its water. The reaction produces considerable heat, so water is released as steam. The chemical equation shows that the sulphuric acid remains uncombined; the sugar is simply reduced to carbon (the black material).
As the steam is given off (the reaction is exothermic), bubbles form that cause the carbon to create a substance that looks like an erupting volcano. On cooling, the substance has the feel of coke.
Sucrose + concentrated sulphuric acid ➪ water as steam + carbon + sulphuric acid C12H22O11(s) + H2SO4(conc) ➪ 11H2O(aq) + 12C(s) + H2SO4(aq)
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