How are the codes (chemical formulas) for pure substances different from those for mixtures?

Answer : The chemical formula of pure substances are different from those of mixtures because all the matter that exists on earth can be classified into two categories namely; pure substances and mixtures.

A pure substance always consists of a single element or compound. Example Oxygen is formed only of oxygen (O) atoms; whereas the table salt which is formed only by sodium chloride (NaCl) molecules is a compound which is made up of pure elements. A pure substance cannot be further divided into its components.

A mixture is made up of different compounds and/or elements. It can be easily separated using any physical method. Example, sand, salt and saw dust mixed together as a mixture. Also, it will not have a definite chemical formula.

Please refer the attachment for better understanding.

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