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Writing Chemical Equation

Define Chemical Equation


A chemical equation can be used todescribe what is happening in chemical reactions and also indentifiesthe starting material which is known as reactants, resultingsubstance which is known as products, the participants formula, thestate of the participants like solid, liquid, or gas, and the amountof each substance. The mathematically balancing relationship betweenthe quantity of the reactants and products is called as balancingchemical equation. The quantities of reactants and products involvedin reaction are expressed as grams or moles.


It takes practice to be able to writingbalanced chemical equation. Writingchemical equations practice the following important steps.

  1. To writing the unbalancedequation, first write the chemical formulas of reactants on the lefthad side of the equation and then write the chemical formulas ofproducts obtained from the reaction on the write hand side of theequation. Finally put the arrow between the reactants and productsto show the direction of the reaction but arrows are facing in bothdirections if the reaction at equilibrium.

  2. To writing balanced chemicalequations apply the law of conservation of mass to get the samenumber of atoms of every element on both the side of the equation.Start by balancing an element which is appears in only one reactantand product. Once one element is balanced then continues to balancethe other elements one by one until all elements are balanced. Sometime write co-efficient in front of the formulas to balance theequation, but do not any subscripts, because they will change theformulas itself.

  3. Finally to indicate the states ofmatter of the reactants and products write the state of matter within the brackets followed by the formula of the substance itdescribes. For example for gaseous substance write (g), for solidsubstance write (s), for liquid substance write (l), and for aqueoussolution write (aq).

Practice WritingChemical Equations

  1. Tin oxide is heated with hydrogengas to form tin metal and water vapor for that write balancing chemical equation.

First write theunbalance equation for above reaction,

SnO2 +H2 -------------> Sn + H2O

Then balance thechemical equation, in above equation, left hand side has 2 oxygenatom but in write hand side only one oxygen atom, to balance theoxygen atom putting a co-efficient of 2 in front of the water.

SnO2 +H2 -------------> Sn +2 H2O

But now they puthydrogen atoms in unbalanced condition. To balance the hydrogenatoms, putting a co-efficient of 2 in front of the hydrogen atom.

SnO2 +2H2 -------------> Sn +2 H2O

Finally to indicatethe states of matter of the reactants and products, write the stateof matter with in the brackets as follows.

SnO2(s) + 2H2 (g) -------------> Sn (s) + 2 H2O(g)

  1. Sodium is reacts with hydrochloricacid to sodium chloride and hydrogen for that write balancedchemical equation.

First write theunbalance equation for above reaction,

Na + HCl-------------> NaCl + H2

Then balance thechemical equation, first balance the hydrogen atoms,

Na + 2HCl-------------> NaCl + H2

Then balance thechlorine atoms,

Na + 2HCl -------------> 2NaCl + H2

Finally balance thesodium atoms,

2Na + 2HCl-------------> 2NaCl + H2

Finally to indicatethe states of matter of the reactants and products, write the stateof matter with in the brackets as follows.

2Na(s) + 2HCl (aq)-------------> 2NaCl (aq) + H2(s)


Writing chemicalequations in word for the following chemical reactions.

  1. Magnesium burns in oxygen to forma magnesium oxide.

Magnesium(s) +oxygen (g) ------------> magnesium oxide (g)

  1. Hydrogen and oxygen gases react toform water.

Hydrogen (g) +oxygen (g) ------------> water (l)