Chemical Reactions and Equations

Writing a Chemical Equation

• Chemical equations can be made more concise and useful by using chemical formulae instead of words.
• A chemical equation represents a chemical reaction.
• The equation Mg + O2 → MgO (1.2) is a skeletal chemical equation for the burning of magnesium in air.
• To check if the equation is balanced, count and compare the number of atoms of each element on the LHS and RHS of the arrow.

Balanced Chemical Equations

• The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction.
• The total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants.
• In other words, the number of atoms of each element remains the same, before and after a chemical reaction.
• A skeletal chemical equation needs to be balanced to satisfy the law of conservation of mass.
• The equation Zn + H2SO4 → ZnSO4 + H2 (1.3) is a balanced chemical equation, as the number of atoms of each element is the same on both sides of the arrow.
• To balance a chemical equation, count and compare the number of atoms of each element on the LHS and RHS of the arrow.
• Then, adjust the coefficients of the reactants and products to make the number of atoms of each element equal on both sides.

Learn about writing chemical equations and representing chemical reactions using chemical formulae. Understand the importance of balancing atoms on the left and right hand side of the equation.