Conversions & Balancing Equations
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Transcript Conversions & Balancing Equations
Mr. Ramos
Conversion means to change something “appearance.”
1ft = 12in is known as a conversion factor
𝐺𝑖𝑣𝑒𝑛 (𝑤𝑖𝑡ℎ 𝑈𝑛𝑖𝑡𝑠) 𝑥
◦ Example: 1 foot = 12 inches
◦ Example: 1 meter = 100 centimeters
𝐶𝑜𝑛𝑣𝑒𝑟𝑠𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 (𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑡 𝑈𝑛𝑖𝑡𝑠 𝑓𝑟𝑜𝑚 𝐺𝑖𝑣𝑒𝑛)
𝐶𝑜𝑛𝑣𝑒𝑟𝑠𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 (𝑆𝑎𝑚𝑒 𝑈𝑛𝑖𝑡𝑠 𝑎𝑠 𝐺𝑖𝑣𝑒𝑛)
Cancel the units of the “Given” with the units of the
conversion factor’s denominator.
The gasoline in an automobile gas tank has a
mass of 60.0 kg and a density of 0.752
g/cm3. What is its volume in cm3?
What is the mass of Hydrogen, Carbon, or
Oxygen?
◦ Go to the periodic table and try to find the
corresponding unit associated with the mass of
these elements.
Hydrogen’s mass is 1.01 what?
Carbon’s mass is 12.01 what?
Oxygen’s mass is 16.00 what?
Where are the UNITS?
The atomic mass unit (amu), or Dalton, is
used to indicate the mass of atoms and
molecules.
◦ Hydrogen has a mass of 1.01 amu
◦ Carbon has a mass of 12.01 amu
◦ Oxygen has a mass of 16.00 amu
If, however, we have a fixed amount of any element that
equals 6.022 x 1023, then the mass of that element is
changed from amu to grams.
1 mole = 6.022 x 1023 (Avogadro’s Number)
The element hydrogen has a mass of 1.01 amu.
The element carbon has a mass of 12.01 amu.
The element oxygen has a mass of 16.00 amu.
Do you notice the pattern?
1 mole of anything contains
6.022 x 1023 particles
◦ However, 1 mole of hydrogen has a mass of 1.01 grams.
◦ However, 1 mole of carbon has a mass of 12.01 grams.
◦ However, 1 mole of oxygen has a mass of 16.00 grams.
1 mole of M&M’s = 6.022 x 1023 M&M’s
◦ That’s a lot of M&M’s (Yummy)
1 mole of U.S. dollars = 6.022 x 1023 U.S. dollars
◦ I would be rich! YES!
1 mole of carbon = 6.022 x 1023 carbon atoms = 12.01
grams of carbon
6CO2 + 6H2O + Sunlight C6H12O6 + 6O2
The formula above represents the photosynthesis
equation.
How many grams of glucose are produced when 12
moles of carbon dioxide are consumed?
Sodium chloride, NaCl, forms by the following
reaction between sodium and chlorine.
◦ 2Na (s) + Cl2 (g) 2NaCl (s)
How many moles of NaCl result from the complete
reaction of 3.4 mol of Cl2? Assume that there is
more than enough Na.
Water is formed when hydrogen gas reacts
explosively with oxygen as according to the
following balanced equation.
◦ O2 (g) + 2H2 (g) 2H2O (g)
How many moles of H2O result from the complete
reaction of 24.6 mol of O2? Assume that there is
more than enough H2.
How many moles of ammonia (NH3) are
produced when 0.60 mol of nitrogen (N2)
reacts with Hydrogen (H2)?
◦ N2 (g) + 3H2 (g) 2NH3 (g)
For any closed system, mass cannot be
created or destroyed.
◦ Mass can only be transferred.
Reactants
Products
Chemical equations must always be balanced.
6CO2 + 6H2O C6H12O6 + 6O2
Carbon = 6
Carbon = 6
Oxygen = 18
Oxygen = 18
Hydrogen = 12
Hydrogen = 12
Reactants
Products
1. Write a skeletal equation by writing
chemical formulas for each of the reactants
and products.
SiO2 (s) + C (s) SiC (s) + CO (g)
SiO2 (s) + C (s) SiC (s) + CO (g)
2. If an element occurs in only one compound on
both sides of the equation, balance it first. If
there is more than one such element, balance
metals before nonmetals.
Begin with Si: 1 Si atom 1 Si atom
Balance O next: 2 O atoms 1 O atom
◦ Si is already balanced
◦ To balance O, put a 2 before CO (g)
◦ SiO2 (s) + C (s) SiC (s) + 2CO (g)
SiO2 (s) + C (s) SiC (s) + 2CO (g)
3. If an element occurs as a free element on
either side of the chemical equation, balance
it last. Always balance free elements by
adjusting the coefficient on the free element.
Balance C: 1 C 3 C
◦ To balance C, put a 3 before C (s)
◦ SiO2 (s) + 3C (s) SiC (s) + 2CO (g)
SiO2 (s) + 3C (s) SiC (s) + 2CO (g)
4. If the balanced equation contains
coefficient fractions, clear these by
multiplying the entire equation by the
appropriate factor.
This step is not necessary in this example.
5. Check to make certain the equation is
balanced by summing the total number of
each type of atom on both sides of the
equation.
SiO2 (s) + 3C (s) SiC (s) + 2CO (g)
Silicon = 1
Silicon = 1
Oxygen = 2
Oxygen = 2
Carbon = 3
Carbon = 3
C8H18 (l) + O2 (g) CO2 (g) + H2O (g)
Fe (s) + 3HCl (aq) FeCl3 (aq) + H2 (g)