If you know how to write and balance chemical equations, you are getting a good deal of your chemistry right. If you still find it a challenge, not a problem. By the end of this article, you would have understood how to balance chemical equations.
Balanced chemical equations show the number of atoms and molecules and the state of matter of each atom that goes into the reaction. It also shows the products of the reactants.
Regardless of how the atoms are distributed in the compounds, each must be balanced on both sides.
What are chemical equations?
Chemical equations are symbolic representations of chemical reactions. They include the reactants, the direction of the reaction, the products, and the factors (heat and catalysts) that influence the reaction.
Some chemical equations also include the state of matter of each molecule. Matter exists as solid(s), liquid(l), gas(g), and aqueous(aq). Heat is represented by the delta (∆) sign.
A chemical equation may be balanced or unbalanced. Both equations are similar except that unbalanced equations do not include the stoichiometric ratio between reactants and products.
How to balance chemical equations
The traditional method (one element after the other)
- The first step in balancing chemical equations is to write out the correct equation
- Compare the coefficients behind each element on each side of the equation and balance them
- Note: subscripts are permanent values and you cannot change them. The coefficients are the only values you can change
- Repeat step two for all other elements in the reaction until both sides are balanced
- Take this equation for instance,
SiCl4 + H2O ———> H4SiO4 + HCl
- Balancing chemical equations gets easier when there is no coefficient
- List out the number of atoms of each element
Left side Right side
Si – 1 Si – 1
Cl – 4 Cl – 1
H – 2 H – 5
O – 1 O – 4
- Start balancing for Cl. Add a coefficient of 4 to HCl
SiCl4 + H2O ———> H4SiO4 + 4HCl
- This makes H on the right side more than the H on the left by 6 moles. The oxygen on the right is also more by 2 moles
- To balance the H and O atoms, add 4 to the H2O
SiCl4 + 4H2O ———> H4SiO4 + 4HCl
Here’s a balanced chemical equation.
The algebraic method
SiCl4 + H2O ———> H4SiO4 + HCl
- Assign variables a, b, c, and d to each species involved in the reaction
aSiCl4 + bH2O ———> cH4SiO4 + dHCl
- Create equations for each element:
Si: a = c
Cl: 4a = d
H: 2b = 4c + d
O: b = 4c
- Then, assume the value of a is 1. Therefore, c also becomes 1 because a = c
- Substitute these values in each equation:
Cl: 4(1) = d, d = 4
O: b = 4(1), b = 4
H: 2b = 4(1) + 4, 2b = 8, b = 4
Therefore, a = 1, b = 4, c = 1, d = 4
- The balanced chemical equation will be:
SiCl4 + 4H2O ———> H4SiO4 + 4HCl
How to balance ionic equations
- Take, Ca2+ + 2Cl– + 2Ag+ + 2NO3– ——–> Ca2+ + 2NO3– + 2AgCl, for example
- When balancing ionic chemical equations, the charge on both sides of the reaction must be equal
- Also, spectator ions (ions present on both sides of the equation) should cancel out each other
- After following the rules above, the net ionic equation will be:
2Cl– + 2Ag+ ———> 2AgCl
- Let us consider the following reaction:
2Ag+(aq) + Cr2O72−(aq) → Ag2Cr2O7(s)
- This reaction shows that two silver ions reacted with the chromate ion to yield silver chromate. The +2 charge on the silver atoms will cancel out the -2 charge on the chromate ion
- Consequently, the charge on both sides of the equation becomes equal
FAQs
Should you include charge when balancing chemical equations?
Charges must be present if you are balancing ionic reactions or oxidation/reduction half-reactions. You may leave out the charge if there is no dissociation of compounds or molecules.
However, the net charge must be the same on both sides of the equation.
Can you balance chemical equations with fractions?
Yes. Some equations are balanced using fractions as the coefficients.
But, the equation should not be left with the fraction coefficients. Multiply both sides of the equation by the denominator of the fraction to give you whole number integers.
Can you balance chemical equations with decimal numbers?
Yes, you can. During the balancing process, decimal numbers can be used as coefficients only. The total number of each atom on each side of the equation must be equal.
However, atoms should have whole-number coefficients. Therefore, you should multiply all decimal coefficients with a number that will turn them into whole-number integers.
Conclusion
Chemical equations show the compounds are factors involved in a chemical reaction and the resulting products. They also show the direction of the reaction.
Chemical equations are not correct until they are balanced. When balancing chemical equations, ensure that there is an equal amount of each atom on both sides of the equation. Moreover, chemical equations must be balanced with whole-number integers.
Thanks for reading.
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