MRC - Mass Relationships in Compounds (Module Overview)
Mass Relationships in Compounds
Introduction
In this module, you will be introduced to the concept of the mole. No, not the dermatological condition or the burrowing rodent, but a term coined by chemists and adopted by the International System of Units as the base unit for measuring the amount of a substance. Calculating moles involves using the molar mass. From that simple calculation, you will build many more conversions that will enable you to solve much more complicated chemical problems in this module and in the next one as well.
Having a periodic table handy is always helpful in chemistry. You may always use a periodic table on assignments, quizzes, and tests in this course.
Download the periodic table. Links to an external site.
As you move through this module, you will realize that knowledge of ions, their charges, how to write formulas, and how to balance equations are all very important skills from previous modules that carry into this module. If you find that you need a review, please revisit the past modules.
A printable copy of an ionic charges chart first presented earlier in this course is found below. You may use this chart on all assignments, quizzes, and tests.
Download the Ionic Charges Chart. Links to an external site.
Module Lessons Preview
In this module, we will study the following topics:
Dimensional Analysis: In this lesson we will revisit the concept of Dimensional Analysis where a conversion factor is used to cancel one unit and introduce another. We used this same process for completing metric conversions in previous modules.
The Mole: In this lesson we will begin very important foundational concepts that will follow you throughout the remainder of the course. We will learn about the mole and Avogadro’s Number, which are often used in conversion factors in chemistry.
Percent Composition & Empirical Formulas: In this lesson we will discuss the relative ratios of elements in chemical compounds. We will learn how to calculate percent composition and empirical formulas. To do this, you will utilize the knowledge of dimensional analysis, molar mass and the unit conversions from the previous lesson to better understand the makeup of various compounds.
Hydrates & Molecular Formulas: In this lesson, we will take percent composition and empirical formulas a step further by completing calculations involving hydrates and molecular formulas.
Key Terms
Equivalence Statement – A statement that shows the quantities and units that are equal to each other
Dimensional Analysis – The sequential application of conversion factors expressed as fractions and arranged so that any dimensional unit can be cancelled out until the desired set of dimensional units is obtained.
Conversion Factor – A ratio expressed as a fraction that equals 1
Avogadro's number - The number of molecules in a mole of a substance, approximately 6.0225 x 1023.
Mole - The amount of a substance that contains as many atoms, molecules, ions, or other elementary units as the number of atoms in 0.012 kilograms of carbon 12. The number is 6.0225 × 1023, or Avogadro's number.
Molar mass - Symbol M, is a physical property characteristic of a given substance, namely its mass per amount of substance. The base SI unit for mass is the kilogram and that for the amount of substance is the mole, thus the derived unit for molar mass is kg/mol. However, for both practical and historical reasons, molar masses are almost always quoted in grams per mole (g/mol).
Molar Volume – The volume of one mole of any gas at standard temperature and pressure
Empirical formula – A chemical formula that represents the lowest whole number ratio of atoms in a molecule
Molecular formula - A chemical formula that shows the exact number and kinds of atoms in a molecule.
Hydrate - A solid compound containing water molecules combined in a definite ratio as an integral part of the crystal.
Percentage composition - The mass percent of each element in a compound.
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