# Stoichiometry How -To

## What is Stoich?

To make things simple, stoichiometry is the science behind recipes. It's how we find out how much of one thing you need to make another. For our example, we have Aluminum and Silver Sulfate coming together to make Aluminum Sulfate.

2Al + Ag2 SO4 = 2Ag + Al2 (SO4) 3

Aluminum(s) + Silver Sulfate(s) = Silver(s) + Aluminum Sulfate(s)

26.982 g/mol + 311.836 g/mol = 107.87 g/mol + 150.02 g/mol

## What is Aluminum Sulfate, and Why is it important?

Aluminum Sulfate is a compound derived through single replacement with Silver Sulfate. (Single replacement is when one element replaces another in a reaction.) It has a real world, practical, use in purifying drinking water.

## Mole to Mole Conversions

How many moles of Aluminum Sulfate are present when 8.2 moles of aluminum is reacted with Silver Sulfate?

To figure out this problem, you have to know how to do a Mole to Mole conversion. First start with your givens, which is 8.2 Moles, and put in in the train track format. You put 8.2 as your given at the start, then on the next spot over, put the amount of moles you need to make one mole of your want. In this case, it takes 2 moles of aluminum to male 1 mole of Aluminum Sulfate. Then you multiply or divide to get your final answer, so 8.2 * 1 /2 = 4.1 moles of Aluminum Sulfate. That's your final answer.

8.2 Mol Al |1 Mol Al2 SO4 3

---------------|-----------------------------

---------------|2 Mol Al

## Theroretical vs. Percent Yields

A theoretical yield is when you calculate how much you can make according to the calculations, while percent yield is how much you actually end up making. Typically due to human error, these numbers can be different. Like in the problem above, if there is a mis-reaction, wrong measurement, or other such flaw, the yields could be different.