A chemical problem may be presented to you in units of moles, mass, or volume. Which one of these can be directly used in arithmetic no matter what the conditions are?
moles
Why moles?
The equations we write represent mols. For example,
2NaOH + H2SO4 ==> 2H2O + Na2SO4
It reads, "two moles of sodium hydroxyde reacts with one mole of H2SO4 to produce 2 moles of water and one mole of sodium sulfate." If we have grams, we must convert to moles first before calculating problems with stoichiometry (moles = grams/molar mass). It it is volume, we must convert to moles first before proceeding (volume/22.4 L = moles).
What this says is that chemicals react by mole ratios, not by grams or by volumes.
To solve chemical problems, it is important to understand the relationship between moles, mass, and volume. Each of these measurements is associated with a different property of a substance. Let's break it down and determine which one can be directly used in arithmetic, regardless of the conditions.
1. Moles (mol): Moles are a unit of measurement for the amount of a substance. They represent a specific number of particles, typically atoms or molecules, in a given sample. The number of moles can be calculated using the mass of the substance and its molar mass. However, for arithmetic calculations, moles are not directly used since they represent a quantity, not a measurable quantity like mass or volume.
2. Mass (g or kg): Mass represents the amount of matter within a substance. It can be directly used in arithmetic calculations. For example, to find the mass of a substance, you simply need to weigh it using a balance, which provides a direct measurement of mass. Mass can be added, subtracted, multiplied, or divided just like any other numerical quantity.
3. Volume (mL, L, cm³, etc.): Volume is the amount of space occupied by a substance. It can also be directly used in arithmetic calculations. If you know the dimensions of the container or the substance's shape, you can calculate its volume. Volume can also be measured using various techniques, such as graduated cylinders for liquids or calculating the dimensions of solids. Like mass, volume can be added, subtracted, multiplied, or divided.
In summary, both mass and volume can be directly used in arithmetic calculations, regardless of the conditions. Moles, on the other hand, are a quantity and generally require additional calculations to determine mass or volume before they can be used in arithmetic calculations.