A chemical equation helps in a variety of ways like: (1) letting us know which is the reactant and which is the product in a chemical reaction. (2) it also helps us to know the ratio at which the reactants combine together to form the products.

In Fe + S = FeS, we know that some atom of iron is reacting with one or more atom of Sulphur to produce Iron Sulfide, but what we don't know is the quantities of each substance involved in this chemical reaction.

For all we know, we may have been given a small sample of iron to use, but if we don't know the number of atoms in this "small iron sample", how do we know the amount of Sulphur that will be enough for the iron.

It's important to have answers to all these questions in an industrial reaction, because one has to know the quantity of reactants needed and the quantity of products to be formed.

<h2 class="title">Quantitative aspects of chemical change: Atomic mass and the mole</h2>
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<p>An equation for a chemical <a data-lesson="what-is-a-reaction-rate" data-subject="chemistry" data-tutorial="energy-and-chemical-reactions" href="https://app.ulearngo.com/chemistry/energy-and-chemical-reactions/what-is-a-reaction-rate">reaction</a> can provide us with a lot of useful information. It tells us what the reactants and the products are in the reaction, and it also tells us the ratio in which the reactants combine to form products. Look at the equation below:</p>

\[\text{Fe} + \text{S} \rightarrow \text{FeS}\]

<p>In this reaction, every atom of iron (\(\text{Fe}\)) will react with a single atom of sulphur (\(\text{S}\)) to form iron sulphide (\(\text{FeS}\)). However, what the equation does not tell us, is the <strong>quantities</strong> or the <strong>amount</strong> of each substance that is involved. You may for example be given a small sample of iron for the reaction. How will you know how many <a data-lesson="chemical-formulas" data-subject="chemistry" data-tutorial="atoms-molecules-ions" href="https://app.ulearngo.com/chemistry/atoms-molecules-ions/chemical-formulas">atoms</a> of iron are in this sample? And how many atoms of sulphur will you need for the reaction to use up all the iron you have? Is there a way of knowing what mass of iron sulphide will be produced at the end of the reaction?</p>
<p>These are all very important questions, especially when the reaction is an industrial one, where it is important to know the quantities of reactants that are needed, and the quantity of product that will be formed. This tutorial will look at how to quantify the changes that take place in chemical reactions.</p>
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Atomic Mass and the Mole

Chemistry generally explores the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances. 

Chemistry

Explore various topics related to the quantitative aspects of chemical change, such as stoichiometry, theoretical yield and percent purity, and learn how to calculate molar mass and concentrations of liquids and gases.


Atomic Mass and the Mole

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