Question

Which is a pure substance?
soda
gasoline
salt water
carbon dioxide

Answer 1

Carbon dioxide

Step-by-step explanation:

Answer 2

Answer: Carbon dioxide is a pure substance.

Explanation: A pure substance is defined when a substance has a single type of molecule. If more than 1 type of molecule is present in a substance, then it is considered as a mixture.

• Soda is basically a mixture of water and carbon dioxide. More than 1 type of molecule is present.

• Gasoline is a mixture of may gases. More than 1 type of molecule is present.

• Salt water contains salt and water molecules, hence it is considered as a mixture.

• Carbon dioxide has only 1 type of molecule which is
  `CO_2` molecules. Hence, it is a pure substance.