Question

State the law of multiple proportions, and give an example of two compounds that illustrate the law.

Short answer

The law states simple whole-number mass ratios of elements in multiple compounds. CO and CO₂ illustrate it with a ratio of 2.

Step-by-step solution

Understand the Law of Multiple Proportions

The law of multiple proportions states that when two elements combine to form more than one compound, the mass ratios of the second element that combine with a fixed mass of the first element are simple whole numbers.

Identify an Example

Identify two compounds made of the same elements that illustrate the law. For this example, use carbon and oxygen, which form carbon monoxide (CO) and carbon dioxide (CO₂).

Determine Mass Ratios

Calculate the mass ratio of oxygen to carbon in each compound. In CO, the ratio is 16:12 (or 4:3) because the molar mass of oxygen is 16 g/mol and that of carbon is 12 g/mol. In CO₂, the ratio is 32:12 (or 8:3) because two oxygen atoms each contribute 16 g/mol.

Compare the Ratios

Compare the mass ratios: the ratio of oxygen in CO₂ to that in CO is \(\frac{32}{12} \bigg/ \frac{16}{12} = 2\). This ratio is a simple whole number (2), perfectly illustrating the law.

Key concepts

mass ratios

The Law of Multiple Proportions focuses on the mass ratios of elements in different compounds. When elements combine to form various compounds, the mass of one element that reacts with a fixed mass of another follows simple whole number ratios.

Consider carbon and oxygen forming two different compounds: carbon monoxide (CO) and carbon dioxide (CO₂).

In CO, the mass ratio of oxygen to carbon is 16:12, or 4:3:

• Oxygen's molar mass = 16 g/mol
• Carbon's molar mass = 12 g/mol

In CO₂, the mass ratio is 32:12, or 8:3:

• Oxygen's molar mass = 16 g/mol (with 2 oxygen atoms)

Comparing these ratios:
\(\frac{32}{12} \bigg/ \frac{16}{12} = 2\)
This shows a simple whole number ratio, illustrating the law. Such ratios make understanding chemical formulas easier and ensure compounds are predictable and systematic.

chemical compounds

A chemical compound consists of two or more elements that are chemically bonded together. The properties of a compound differ from its constituent elements.

For instance, carbon monoxide (CO) and carbon dioxide (CO₂) contain carbon and oxygen, yet have distinct properties:

• CO: Used in fuel production and can be toxic.
• CO₂: Common in respiration and photosynthesis.

Compounds form by specific mass ratios, as explained by the Law of Multiple Proportions. Knowing these ratios helps us understand how elements interact and combine in fixed, predictable ways.

carbon and oxygen

Carbon and oxygen are two essential elements that form numerous compounds. Understanding how these elements combine is crucial in chemistry.

In carbon compounds with oxygen, CO and CO₂ are common:

• Carbon Monoxide (CO): Formed with a 1:1 ratio of carbon to oxygen.
• Carbon Dioxide (CO₂): Formed with a 1:2 ratio of carbon to oxygen.

These combinations highlight how different ratios result in different properties and uses:

• CO is used in industrial processes but is hazardous when inhaled.
• CO₂ is vital for plant life and is a significant greenhouse gas.

Studying the mass ratios in which carbon and oxygen combine enriches our understanding of chemical reactions and compounds.