Question

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

(d) ethene is burnt in the presence of oxygen to form carbon dioxide, and water and releases heat and light.

Answer 1

Balanced chemical equation:

• A chemical equation is a symbolic statement of any chemical reaction where the reactants and products are replaced by their chemical formulae and symbols.
• A balanced equation for a chemical reaction is where the number of atoms and charge of each chemical element is equal in both reactants and products.

Word equation to symbolic equation:

• The Chemical formula for ethene is ${\mathrm{C}}_2{\mathrm{H}}_4$
• The Chemical formula for Carbon dioxide is ${\mathrm{CO}}_2$
• The Chemical formula for Oxygen is ${\mathrm{O}}_2$
• The skeletal chemical equation is
  ${\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Balancing the Chemical Equation:

• We will tabulate the number of atoms of each element on the reactant as well as on the product side.

Element	Reactant side	Product Side
C	2	1
H	4	2
O	2	3

• From the table, it is clear that the Atoms of all elements are not balanced.
• For balancing theatoms we will make the coefficient of ${\mathrm{O}}_2,{\mathrm{CO}}_2,\&{\mathrm{H}}_2\mathrm{O}$ as $3,2\&2$ Respectively. The equation becomes,
  ${\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$
  

Element	Reactant side	Product Side
C	2	2
H	4	4
O	6	6

• The chemical equation is balanced.
• The given reaction is a combustion reaction.
  

Hence, the final balanced chemical equation is ${\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$. The given reaction is a combustion reaction.