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# Stoichiometry

These are the instructions for your Solar System Prezitation. Follow this Prezitation carefully to see what needs to be included.
by

## Emma Walsh

on 27 February 2011

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#### Transcript of Stoichiometry

Double click anywhere & add an idea Stoichiometry Must use a balanced reaction...why?

Matter can neither be created nor destroyed (Law of Conservation of Mass) MOLE to MOLE Stoichiometry To find the limiting reagent: 1. Figure out the number of moles of each reactant using the mole map
2. Divide the number of moles of each reactant by the coefficients
3. The reactant whose moles (coefficient) is lower is the limiting reagent If you try to use a reaction like H + O H O: ***You will have one oxygen atom
that does not get used If yo Mole to Particles MASS to MASS Stoichiometry Solving Stoichiometry Problems:

Step 1: Write the balanced equation

Step 2: What do you know? What are you looking for? SET UP YOUR PROBLEM!!!

Step 3: Make a chart being sure that your units cancel out. Always start your chart with the given information Mole to Mass Definition: The portion of chemistry
dealing with numerical relationships
in chemical reactions; the calculation
of quantities of substances involved
in chemical equations.! The Link is here: 2 2 2 Coefficients tell you the relative
amounts of products and reactants
Coefficients are in units of moles Example: N + 3H 2NH 2 2 3
Coefficients
N
H
NH 2 2 3 Using the coefficients we can write mole ratios Definition: The whole-number ratios between components of a balanced chemical reaction For each 1 mole of N , 3 moles of H are required
For each 1 mole of N , 2 moles of NH will be produced
For 3 moles of H , 2 moles of NH will be produced 2 2 2 3 2 3 Interpret the following BALANCED equation: 2Al O (l) 4Al (s) + 3O (g)

2 3 2 2 moles of Al O decompose to produce 4 moles of Al and 3 moles of O

What is the mole ratio between aluminum oxide and aluminum? 1:2

What is the mole ratio between aluminum and oxygen? 4:3

What is the mole ratio between aluminum oxide and oxygen? 2:3 2 3 2 ***Conversion factor to remember***

1 mole of a substance = molar mass of that substance (grams)
If you are given 6 moles of H , how many moles of N do you need?

If you are given 0.5 moles of H , how many moles of N do you need?

You can flip the mole ratios around if you are asked the following:
- If you are given 4 moles of N , how many moles of H do you need?

Use the same method for finding the amount of product that will be produced.
- Given 6 moles of H , how much NH will be made? 2 2 2 2 2 2 2 3 If I have 4.04 grams of H , how much NH can I make?

1. Use the "mole map" to go from grams of H to moles of H
2. Use mole ratios from our balanced equation to find moles of NH
3. Use the "mole map"to go from moles NH to grams NH 2 3 2 2 3 3 3 How many grams
of iron will be needed
to produce 4 moles of
Fe O ? 3 4 3Fe + 2O Fe O 2 3 4 How many molecules of H are produced by the reaction of tin with 20.0 L HF at STP? Sn (s) + 2HF (g) SnF (s) + H (g) 2 2 2 Mole to Volume How many liters of HF are needed
to produce 9.40 L of H at STP? Sn (s) + 2HF (g) SnF (s) + H (g) 2 2 2 Limiting Reagent Problems limiting reagent - any reactant that is used up first in a chemical reaction; it determines the amount of product that can be formed in the reaction excess reagent - a reagent present in a quantity that is more than sufficient to react with a limiting reagant; any reactant that remains after the limiting reagent is used up in a chemical reaction To figure out how many of each product is produced: 1. Use the moles of the limiting reagent only
2. Use the mole ratio to figure out the moles of each product To figure out how much excess reagent is left: 1. Start with the
moles of the limiting
reagent 2. Use the mole ratio
to figure out the moles
of excess reagent needed 3. Use the mole map
to convert back to grams 4. Subtract this number
from the amount of excess
reagent you started with.
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