A Beginner's Guide to Balancing Chemical Equations

What cannot be changed when balancing chemical equations?

• Reactants

• Products

• Subscripts

• Coefficients

What does a subscript in a chemical formula indicate?

• The number of products

• The number of atoms in a molecule

• The number of reactions

• The number of molecules

What is produced when hydrogen combusts with oxygen?

• Carbon dioxide

• Hydrogen peroxide

• Methane

• Water

What is the correct coefficient for H2 when balancing the combustion of hydrogen?

• 3

• 4

• 2

• 1

What is the main product when methane (CH4) burns completely?

• Hydrogen gas

• Water

• Carbon dioxide

• Carbon monoxide

How many molecules of water are produced when methane combusts completely?

• 1

• 2

• 3

• 4

In real life, what is the balanced equation for the decomposition of hydrogen peroxide (H2O2)?

• 2H2O2 -> 2H2O + O2

• 2H2O2 -> 2H2 + O2

• 2H2O2 -> 2H2 + O2

• H2O2 -> H2 + O2

Answer explanation

In real life, hydrogen peroxide breaks down into H2O (water) and O2 (oxygen gas), not H2 (hydrogen gas). If it broke down into H2, it would explode with a spark or flame!

What must be added to balance the equation when sodium (Na) reacts with chlorine gas (Cl2) to form table salt (NaCl)?

• 1 Na, 2 Cl2

• 2 Na, 1 Cl2

• 1 Na, 1 Cl2

• 2 Na, 2 NaCl

In the reaction of silver sulfide producing silver and sulfur, what is the correct coefficient for silver (Ag) to balance the equation?

• 16

• 8

• 32

• 1

When balancing the combustion of a hydrocarbon (C7H8), what is the correct coefficient for oxygen (O2)?

• 18

• 14

• 9

• 7