define unbalance chemical equations
Answers
Balanced and Unbalanced equations. ... Such an equation which has an unequal number of atoms of one or more elements in reactants and products is called unbalanced chemical equation.Unbalanced chemical equation has to be made balanced to justify the law of conservation of mass.
Answer:
A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge are the same for both the reactants and the products. In other words, the mass and the charge are balanced on both sides of the reaction
Explanation:
Balancing chemical equations involves the addition of stoichiometric coefficients to the reactants and products. This is important because a chemical equation must obey the law of conservation of mass and the law of constant proportions, i.e. the same number of atoms of each element must exist on the reactant side and the product side of the equation.
Two quick and easy methods of balancing a chemical equation are discussed in this article. The first method is the traditional balancing method and the second one is the algebraic balancing method.
The Traditional Balancing Method
The first step that must be followed while balancing chemical equations is to obtain the complete unbalanced equation. In order to illustrate this method, the combustion reaction between propane and oxygen is taken as an example.
Step 1
In this example, the coefficient is first assigned to carbon, as tabulated below.
Chemical Equation: C3H8 + O2 → 3CO2 + H2O
Reactant Side Product Side
3 Carbon atoms from C3H8 3 Carbon atoms from CO2
8 Hydrogen atoms from C3H8 2 Hydrogen atoms from H2O
2 Oxygen atoms from O2 7 Oxygen atoms, 6 from CO2 and 1 from H2O
Step 4
Step 3 is repeated until all the number of atoms of the reacting elements are equal on the reactant and product side. In this example, hydrogen is balanced next. The chemical equation is transformed as follows.
Chemical Equation: C3H8 + O2 → 3CO2 + 4H2O
Reactant Side Product Side
3 Carbon atoms from C3H8 3 Carbon atoms from CO2
8 Hydrogen atoms from C3H8 8 Hydrogen atoms from H2O
2 Oxygen atoms from O2 10 Oxygen atoms, 6 from CO2 and 4 from H2O
Now that the hydrogen atoms are balanced, the next element to be balanced is oxygen. There are 10 oxygen atoms on the product side, implying that the reactant side must also contain 10 oxygen atoms.
Each O2 molecule contains 2 oxygen atoms. Therefore, the stoichiometric coefficient that must be assigned to the O2 molecule is 5. The updated chemical equation is tabulated below.
Chemical Equation: C3H8 + 5O2 → 3CO2 + 4H2O
Reactant Side Product Side
3 Carbon atoms from C3H8 3 Carbon atoms from CO2
8 Hydrogen atoms from C3H8 8 Hydrogen atoms from H2O
10 Oxygen atoms from O2 10 Oxygen atoms, 6 from CO2 and 4 from H2O
Step 5
Once all the individual elements are balanced, the total number of atoms of each element on the reactant and product side are compared once again.
If there are no inequalities, the chemical equation is said to be balanced.
In this example, every element now has an equal number of atoms in the reactant and product side.
Therefore, the balanced chemical equation is C3H8 + 5O2 → 3CO2 + 4H2O.
The Algebraic Balancing Method
This method of balancing chemical equations involves assigning algebraic variables as stoichiometric coefficients to each species in the unbalanced chemical equation. These variables are used in mathematical equations and are solved to obtain the values of each stoichiometric coefficient. In order to better explain this method, the reaction between glucose and oxygen that yields carbon dioxide and water has been considered as an example.
Step 1
The unbalanced chemical equation must be obtained by writing the chemical formulae of the reactants and the products.
In this example, the reactants are glucose (C6H12O6) and oxygen (O2) and the products are carbon dioxide (CO2) and water (H2O)
The unbalanced chemical equation is C6H12O6 + O2 → CO2 + H2O
Step 2
Now, algebraic variables are assigned to each species (as stoichiometric coefficients) in the unbalanced chemical equation. In this example, the equation can be written as follows.
aC6H12O6 + bO2 → cCO2 + dH2O
Now, a set of equations must be formulated (between the reactant and product side) in order to balance each element in the reaction. In this example, the following equations can be formed.
The equation for Carbon
On the reactant side, ‘a’ molecules of C6H12O6 will contain ‘6a’ carbon atoms.
On the product side, ‘c’ molecules of CO2 will contain ‘c’ carbon atoms.
In this equation, the only species containing carbon are C6H12O6 and CO2.
Therefore, the following equation can be formulated for carbon: 6a = c
The equation for Hydrogen
The species that contain hydrogen in this equation are C6H12O6 and H2
‘a’ molecules of C6H12O6 contains ‘12a’ hydrogen atoms whereas ‘d’ H2O molecules will contain ‘2d’ hydrogen atoms.
Therefore, the equation for hydrogen becomes 12a = 2d.
Simplifying this equation (by dividing both sides by 2), the equation becomes:
6a = d