Discovering chemistry
Discovering chemistry

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Discovering chemistry

2.2 Some further examples of chemical equations

In this section you will get some practice constructing chemical equations.

  • If you watched the ‘trailer’ for this module, you will have seen a young chemist combining hydrogen (H2) and oxygen (O2) to form water (with a bang!). Write a balanced chemical equation for this reaction.

  • equation left hand side two times cap h sub two times open g close plus cap o sub two of g equals right hand side two times cap h sub two times cap o of l
    Equation label: (5.3)

Next, a chemical equation to represent a reaction on which our very existence depends.

The reaction of the simple sugar glucose is vital to the generation of energy within the body. Glucose has a complicated molecular structure but it can be represented by the formula C6 H12O6.

  • The chemical equation for the reaction between glucose and oxygen to give carbon dioxide and water is:

    cap c sub six times cap h sub 12 times cap o sub six postfix times open s close plus six times cap o sub two postfix times equation left hand side open g close equals right hand side six times cap c times cap o sub two postfix times open g close plus six times cap h sub two times cap o of l
    Equation label: (5.4)

    Show that this equation is balanced.

  • On the left of the equation, there are 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms from glucose and a further 12 oxygen atoms from oxygen molecules, a total of 6C, 12H and 18O. On the right, there are 6 carbon and 12 oxygen atoms from carbon dioxide plus 12 hydrogen atoms and 6 oxygen atoms from water, a total of 6C, 12H and 18O. This is a balanced chemical equation. And, as ever, the atoms have simply been rearranged in the reaction.

So, up to this point, you have seen how a balanced chemical equation can encompass a lot of information about a reaction.

It not only identifies the reactants and products and their respective formulas but also indicates the relative numbers of each reactant molecule and the relative numbers of each product molecule. It also shows, in the example above, that carbon from the glucose molecules ends up in carbon dioxide molecules, the hydrogen produces water and the oxygen in the product molecules comes both from the glucose molecules and from molecular oxygen.

Now for some more practice.

  • Write balanced equations for the reactions represented in (a)–(d).

    FeO + H2 go to Fe + H2O
    Fe2O3+ H2 go to Fe + H2O
    N2+ H2 go to NH3
    CH4+ Cl2 go to CH2Cl2+ HCl
  • The balanced equations are as follows.

    FeO + H2= Fe + H2O
    Equation label: (5.5)
    Fe2O3+ 3H2 = 2Fe + 3H2O
    Equation label: (5.6)
    N2+ 3H2= 2NH3
    Equation label: (5.7)
    CH4+ 2Cl2= CH2Cl2+ 2HCl
    Equation label: (5.8)

As promised in the introduction, in this part of the module you will be making a few excursions into the word of explosive materials and looking at the chemical reactions involved. Your starting point, in the next section is gunpowder.


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