Skip to main content
Ch.3 - Molecules, Compounds & Chemical Equations
Chapter 3, Problem 79a

Write a ratio showing the relationship between the molar amounts of each element for each compound. (See Appendix IIA for color codes.) (a)
Illustration of molecular structures showing the Law of Definite Proportions in compounds.

Verified step by step guidance
1
Identify the elements present in the molecular structures shown in the image. The blue spheres represent one element, and the red spheres represent another element.
Count the number of blue spheres and red spheres in one molecule to determine the ratio of the elements in a single molecule.
Observe that each molecule consists of one blue sphere and three red spheres.
Write the ratio of the molar amounts of the elements in the compound. Since there is one blue sphere for every three red spheres, the ratio is 1:3.
Express the ratio in terms of the elements, for example, if the blue sphere represents element A and the red sphere represents element B, the ratio of A to B in the compound is 1:3.

Verified Solution

Video duration:
52s
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Ratio

A molar ratio is a relationship between the amounts of different substances in a chemical reaction, expressed in moles. It is derived from the coefficients of a balanced chemical equation and indicates how many moles of one substance react with or produce moles of another. Understanding molar ratios is essential for stoichiometric calculations, allowing chemists to predict the quantities of reactants and products involved in a reaction.
Recommended video:
Guided course
02:14
Neutron-Proton Ratio

Law of Definite Proportions

The Law of Definite Proportions states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the sample size or source. This principle is fundamental in chemistry as it ensures that compounds have consistent compositions, which is crucial for understanding chemical formulas and reactions. For example, water (H2O) always consists of two hydrogen atoms and one oxygen atom.
Recommended video:
Guided course
02:48
Law of Definite Proportions

Chemical Formula

A chemical formula is a symbolic representation of a compound that indicates the types and numbers of atoms present. It provides essential information about the composition of a substance, such as the ratio of elements in a compound. For instance, the formula C6H12O6 for glucose shows that it contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms, reflecting the specific molar ratios of these elements.
Recommended video:
Guided course
02:26
Skeletal Formula