1. Stoichiometry

2. To start the equation must be balanced.
Balanced means the same number of each type of atom before and after the arrow.
Zn + HCl  ZnCl2 + H2
2 x 1 Zn H Cl 1 2
Multiply to even the sides. The number used to multiply the number of atoms becomes the coeffiecent.
Zn HCl  ZnCl2 + H2

3. You will start with one of these
The road map is to help you navigate through stoichiometry
How many moles of HCl is needed to react with
6 mol of Zn?
The number, measurement unit and substance in the question statement determine what to use to start.
You will start with one of these
Zn is now substance A.
Because the unit is mol the 6 goes in the second circle.
1 mol A 6
____ g A
= ___ mol A
Molar g A
mass
Find the molar mass from the periodic table

4. The road map is to help you navigate through stoichiometry
This ratio comes from the balanced equation
How many moles of HCl is needed to react with 6 mol of Zn A
Zn HCl  ZnCl2 + H2 1 2 2
ratio is 1 Zn to 2 HCl 12
____ g A
1 mol A 6
___ mol B
= ____ mol B
= ___ mol A
Molar g A
mass
____ mol A
Zn is substace A
The queston is about HCl so HCl is substance B
There is no number in front of Zn so it gets a 1

5. You will start with one of these
The road map is to help you navigate through stoichiometry
How many moles of HCl is needed to react with
100 grams of Zn?
The number, measurement unit and substance in the question statement determine what to use to start.
You will start with one of these
Zn is now substance A.
Because the unit is grams the 100 goes in the first circle.
100
1 mol A
____ g A
= ___ mol A
Molar g A
mass
Find the molar mass from the periodic table

6. Molar Mass only needs calculated if using grams.
Zn HCl  ZnCl2 + H2
If you need the molar mass (gram formula mass).
Look up the mass of each element on the periodic table.
H = g
Cl = g
Zn = g
Calculate the molar mass of substance in the equation.
Zn = g
H2 = x 2 = 2.016
HCl = =
ZnCl2 = (35.45) =
Molar Mass only needs calculated if using grams.

7. How many moles of HCl is needed to react with 100 grams of Zn?
HCl is substance B
How many moles of HCl is needed to react with
100 grams of Zn?
This ratio comes from the balanced equation
Zn is substance A
Zn HCl  ZnCl2 + H2 1 2 2
ratio is 1 Zn to 2 HCl
1 mol A
100
1.53
___ mol B
3.06
____ g A
= ____ mol A
= _____ mol B
___ mol A
g A
Find the molar mass from the periodic table
65.37g Zn = 1 mol Zn
65.37

8. The road map is to help you navigate through stoichiometry
HCl is substance B in grams
How many grams of HCl is needed to react with
6 mol of Zn?
Find the molar mass from the periodic table
Zn is substance A in mol
Zn HCl  ZnCl2 + H2 1 2 2
1 Mol HCl = g HCl
36.458g
This ratio comes from the balanced equation
ratio is 1 Zn to 2 HCl
Molar g B
mass
1 mol A 6
___ mol B 12
= _____ g B
____ g A
= ____ mol A
= ___ mol B
Molar A
mass
___ mol A
1 mol B
Find the molar mass from the periodic table
65.37g Zn = 1 mol Zn
Not needed substance A is mol

9. The road map is to help you navigate through stoichiometry
HCl is substance B in grams
How many grams of HCl is needed to react with
100 g of Zn?
Find the molar mass from the periodic table
Zn is substance A in grams
Zn HCl  ZnCl2 + H2 1 2 2
1 Mol HCl = g HCl
36.458g
This ratio comes from the balanced equation
ratio is 1 Zn to 2 HCl
Molar g B
mass
1 mol A
100
1.53
___ mol B
= ____ g B
111.56
____ g A
= ____ mol A
= ____ mol B
3.06
Molar A
mass
___ mol A
1 mol B
Find the molar mass from the periodic table
65.37g Zn = 1 mol Zn
65.37g A