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

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 molecules. Hence, it is a pure substance.

The answer to this problem is. 67

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