Counting Atoms

Front

What is an element?

Back

A substance that cannot be broken down into simpler substances by chemical means. Examples include hydrogen (H), oxygen (O), and carbon (C).

Front

How many elements are in the compound O₂?

Back

1 (Oxygen is the only element present in the compound O₂).

Front

How many elements are in the chemical formula HCl?

Back

2 (Hydrogen and Chlorine are the two elements present).

Front

What is a coefficient in a chemical equation?

Back

A number placed in front of a chemical formula to indicate how many molecules or atoms are involved in the reaction.

Front

How many atoms of aluminum are in the equation 4Al + 3O₂ --> 2Al₂O₃?

Back

4 (There are 4 aluminum atoms on the left side of the equation).

Front

What does it mean for a chemical equation to be balanced?

Back

A balanced equation has the same number of each type of atom on both sides of the equation, indicating that mass is conserved.

Front

What coefficient should be used to balance the equation N₂ + O₂ --> _NO?

Back

2 (The balanced equation is N₂ + O₂ --> 2NO).

Front

Is the equation Fe + S --> FeS balanced or unbalanced?

Back

Balanced (There is one iron atom and one sulfur atom on both sides of the equation).

Front

What is the law of conservation of mass?

Back

In a chemical reaction, matter is neither created nor destroyed; the total mass of reactants equals the total mass of products.

Front

What is a chemical formula?

Back

A representation of a substance using symbols for its constituent elements and numbers to indicate the ratio of atoms.