Solving Stoichiometry Problem STEP-BY-STEP MASS TO MOLE
Slide 2
What is Stoichiometry Stoichiometry is the study of the
relationships or ratios between two or more substances undergoing a
physical or chemical change
Slide 3
We will be taking steps to solve the different equations The
type of problem we will look at is solving for a Gram to Moles,
Stoichiometry problem. Lets start with the problem. KBr+ Cl 2 KCl +
Br 2 Potassium bromide reacts with chlorine gas to produce
potassium chloride and iodine gas. How many moles of bromine gas
can be produced from 100g of potassium bromide
Slide 4
Solving Stoichiometry Problems Step 1. Balancing the Equation A
balanced equation has equal numbers of each type of atom on each
side of the equation. Chemical equations usually do not come
already balanced. Making sure they are balanced must be done before
the equation can be used in any chemically meaningful way. So we
need to look at our problem and make sure that our equation is
balanced KBr+ Cl 2 KCl + Br 2 This equation is not balanced, so we
need to balance it. 2KBr+ Cl 2 2KCl + Br 2
Slide 5
Step 2: Find the Given Potassium bromide reacts with chlorine
gas to produce potassium chloride and iodine gas. How many moles of
bromine gas can be produced from 100g of potassium bromide After
reading the equation again, find what is Given We are given 100 g
of Potassium bromide We need Moles of bromine gas
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Step 3: Look for the ratio of moles Look for the Ratio of moles
in the equation After the equation is balanced, the coefficient
basically is saying that that is how many moles of that substance
is needed to make the reaction If we have: 2KBr+ Cl 2 2KCl + Br 2
Basically what is being said is that you need: 2KBr + 1 Cl 2 to
make 2KCl + 1Br 2 These coefficients make up the mole ratio 2:1:2:1
So it takes 2 mole of KBr and 1 moles of Cl 2 to make 2 moles of
KCl and 1 mole of Br 2
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Step 4: Lets Set up the Equation The problem states If you
start with 100g of Potassium Bromide, how many moles of bromine gas
will be produced? So lets set up the problem : We are given 100g
KBr we are looking for moles of Br 2. In order to solve this we
need to find the Molar Mass of KBr to get rid of grams of KBr (I
will round to the nearest whole number) K-39 Br-80 Add them up you
get 119g of KBr Set up the T-Chart 100 gm KBr 119g KBr
Slide 8
Step 4: Lets Set up the Equation The problem states If you
start with 100g of Potassium Bromide, how many moles of bromine
will be produced? We know that 1mole of any molecule is equal to
the molar mass of that molecule: So on top of the 119gm of KBr, I
will have 1mole of KBr But I need to solve for Br 2, so I need to
cancel my mole of KBr Set up the T-Chart 100 g KBr 119g KBr 1 mol
KBr
Slide 9
Step 5: Look at my Mole Ratio The problem states If you start
with 100g of Potassium Bromide, how many moles of Bromine gas will
be produced? As stated I need to solve for Br 2, so I need to
cancel my mole of KBr So now I will look at my mole ratio 2KBr+ Cl
2 2KCl + Br 2 2: 1: 2: 1 I have 2 mole of KBr based off my ratio I
place that on the bottom so that I can cancel mol of KBr Then I
look at what I need, I need moles of Br 2 So I put the mole ratio
for B 2 on top Set up the T-Chart 100 g KBr 119g KBr 1 mol KBr 1
mol of Br 2 2mol KBr
Slide 10
Step 6: Cancel Units and Do the Math Set up the T-Chart 100 g
KBr 119g KBr 1 mol KBr 1 mol of Br 2 2mol KBr 0.42 mol Br 2
