AI Tutor
Most industrial chemicals, from life-saving pharmaceuticals to commercial fertilizers, cannot be manufactured in a single chemical reaction.
Instead, chemical plants link multiple reactions in a sequence where the output of one vessel becomes the starting feed for the next. A chemical species formed in an early stage and consumed in a later stage is called an intermediate.
How do we track mass through these chemical chains when the intermediate species keep changing?

The Mole Bridge

Mass cannot be transferred directly between different substances because different molecules have different masses. We must convert mass into moles, which measure the exact count of chemical particles.
To find moles (nn), we divide mass in grams (mm) by the substance's molar mass (MM, in g/mol\text{g/mol}): n=mMn = \frac{m}{M}
Let's put this pathway into action with a real manufacturing sequence.

Worked Example: The Contact Process

In 1831, British vinegar maker Peregrine Phillips patented the Contact Process to produce sulfuric acid (extH2extSO4 ext{H}_2 ext{SO}_4) on an industrial scale.
Suppose an industrial plant roasts 480.0extg480.0 ext{ g} of iron pyrite (extFeS2 ext{FeS}_2, M=120.0extg/molM = 120.0 ext{ g/mol}) through this sequential two-step process:
Step 1: 4extFeS2(s)+11extO2(g)→2extFe2extO3(s)+8extSO2(g)\text{Step 1: } 4 ext{FeS}_2(s) + 11 ext{O}_2(g) \rightarrow 2 ext{Fe}_2 ext{O}_3(s) + 8 ext{SO}_2(g)