Chemical Formulas

Front

What is a chemical formula?

Back

A chemical formula is a way of expressing the composition of a substance using symbols for its constituent elements and numbers to indicate the ratio of atoms.

Front

What does a subscript in a chemical formula indicate?

Back

A subscript indicates the number of atoms of the element in a molecule. For example, in H₂O, the '2' indicates there are two hydrogen atoms.

Front

What does a coefficient in a chemical equation represent?

Back

A coefficient indicates the number of molecules or moles of a substance involved in a reaction. For example, in 2H₂ + O₂ → 2H₂O, the '2' before H₂O means there are two molecules of water produced.

Front

What is the difference between an element and a compound?

Back

An element is a pure substance made of only one type of atom, while a compound is made of two or more different types of atoms chemically bonded together.

Front

What is the chemical formula for sulfuric acid?

Back

H₃SO₄

Front

What are the products of the decomposition of ammonia (NH₃)?

Back

The products are nitrogen gas (N₂) and hydrogen gas (H₂).

Front

Which of the following is a chemical change: iron rusting, water evaporating, wood burning, or food rotting?

Back

Iron rusting, wood burning, and food rotting are chemical changes; water evaporating is a physical change.

Front

What is the chemical formula for carbon dioxide?

Back

CO₂

Front

What does the term 'reactants' refer to in a chemical reaction?

Back

Reactants are the starting substances that undergo a chemical change to form products.

Front

What is the law of conservation of mass?

Back

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.