iiiiiiivv if the 4 young ladies in the front row have a combined weight of 2.15x10 11 micrograms....
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A.Signs of a Chemical Reaction n Evolution of heat and light n Formation of a gas n Formation of a precipitate n Color changeTRANSCRIPT
I II III IV V
If the 4 young ladies in the front row have a combined
weight of 2.15x1011micrograms. What is the average
weight of each? Convert their weight to Pounds!
World’s Most Dangerous Bellringer
I II III IV V
I. Intro to Reactions
Ch. 9 – Chemical Reactions
A.Signs of a Chemical Reaction Evolution of heat and light Formation of a gas Formation of a precipitate Color change
A. Chemical Equations
A+B C+DREACTANTS PRODUCTS
A. Chemical Equations
B. Writing Equations
Identify the substances involved. Use symbols to show:
2H2(g) + O2(g) 2H2O(g)
How many? - coefficient Of what? - chemical formula
Remember the diatomic elements.
In what state? - physical state
B. Writing Equations
Two atoms of aluminum react with three units of aqueous copper(II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride.
• How many?• Of what?• In what state?
Al 2 (s) + 3CuCl2(aq) 3 Cu(s) + 2AlCl3(aq)
C. Describing Equations Describing Coefficients:
individual atom = “atom” covalent substance = “molecule” ionic substance = “unit”
3 molecules of carbon dioxide
2 atoms of magnesium
4 units of magnesium oxide
3CO2
2Mg
4MgO
D. Balancing Equations
An equation is balanced when it has the same # and kind of atoms.
D. Balancing Equations Law of Conservation of Mass: mass is
neither created nor destroyed in a chemical reaction (Lavoisier)
4 H
2 O
4 H
2 O4 g 32 g
36 g
total mass stays the same; atoms can only rearrange.
D. Balancing Steps1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make #s equal.
Coefficient subscript = # atoms
3MgCl2 4Ca(OH)2
4. Reduce coefficients to lowest possible ratio, if necessary.
5. Double check atom balance!!!
D. Helpful Tips
Balance one element at a time. Update ALL atom counts after adding
a coefficient. If elements appear more than once
per side, balance them last. Balance polyatomic ions as single
units. “1 SO4” instead of “1 S” and “4 O”