The Chemical Equation

Science — Second Preparatory

Applications and examples

Comparison aspect	Main idea	Keywords
Experiment 1: zinc and hydrochloric acid.	Put a piece of zinc in a test tube containing hydrochloric acid. Bubbles of hydrogen gas appear. The balanced equation is Zn + 2HCl → ZnCl₂ + H₂. Check the masses: 65 + 2 × 36.5 = 138 and 136 + 2 = 138	piecetesttubecontaining
Experiment 2: sodium and water.	The equation is 2Na + 2H₂O → 2NaOH + H₂. Check the masses: 2 × 23 + 2 × 18 = 82 and 2 × 40 + 2 = 82	equation2H₂O2NaOHCheck
Example from life	The combustion of methane the main part of natural gas is written as a balanced equation so that engineers can calculate the amount of oxygen needed for complete burning and set the air supply of a gas cooker or a power station to achieve it	combustionmethanemainpart

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