Transcript Conversions & Balancing Equations

Mr. Ramos
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Conversion means to change something “appearance.”
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1ft = 12in is known as a conversion factor
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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.
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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?
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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.
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Hydrogen’s mass is 1.01 what?
Carbon’s mass is 12.01 what?
Oxygen’s mass is 16.00 what?
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Where are the UNITS?
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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
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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)
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The element hydrogen has a mass of 1.01 amu.
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The element carbon has a mass of 12.01 amu.
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The element oxygen has a mass of 16.00 amu.
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Do you notice the pattern?
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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.
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1 mole of M&M’s = 6.022 x 1023 M&M’s
◦ That’s a lot of M&M’s (Yummy)
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1 mole of U.S. dollars = 6.022 x 1023 U.S. dollars
◦ I would be rich! YES!
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1 mole of carbon = 6.022 x 1023 carbon atoms = 12.01
grams of carbon
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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?
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Sodium chloride, NaCl, forms by the following
reaction between sodium and chlorine.
◦ 2Na (s) + Cl2 (g)  2NaCl (s)
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How many moles of NaCl result from the complete
reaction of 3.4 mol of Cl2? Assume that there is
more than enough Na.
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Water is formed when hydrogen gas reacts
explosively with oxygen as according to the
following balanced equation.
◦ O2 (g) + 2H2 (g)  2H2O (g)
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How many moles of H2O result from the complete
reaction of 24.6 mol of O2? Assume that there is
more than enough H2.
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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)
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For any closed system, mass cannot be
created or destroyed.
◦ Mass can only be transferred.
Reactants
Products
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Chemical equations must always be balanced.
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6CO2 + 6H2O  C6H12O6 + 6O2
Carbon = 6
Carbon = 6
Oxygen = 18
Oxygen = 18
Hydrogen = 12
Hydrogen = 12
Reactants
Products
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1. Write a skeletal equation by writing
chemical formulas for each of the reactants
and products.
SiO2 (s) + C (s)  SiC (s) + CO (g)
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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.
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Begin with Si: 1 Si atom  1 Si atom
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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)
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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)
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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.
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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
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C8H18 (l) + O2 (g)  CO2 (g) + H2O (g)
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Fe (s) + 3HCl (aq)  FeCl3 (aq) + H2 (g)