Transcript Gaining and losing electrons

Understand the difference between molar
mass and formula weight
▪ Formula weight – weight of one molecule in
units of amu,
▪ Molar mass – weight of one mole of molecules
in grams (per mole).
Know how to determine the
▪ Formula weight – in amu and in grams
▪ Molar mass – in grams
o Know that these two are numerically the
same but different in units
Avogadro’s number and Molar Mass
▪ Define Avogadro’s # as the mole (a counting
unit)
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1 amu = 1.66 x 10 grams
1 mole = 6.02214199 x 1023
Like
1 dozen = 12
Glucose, C6H12O6
Formula weight: 180 amu
Molar mass: 180 g/mole
How much does one glucose molecule weigh?
How much does one mole of glucose molecules
weigh?
Urea, (NH2)2CO
Formula weight: 60.0 amu
Molar mass: 60.0 g/mole
How much does one urea molecule weigh?
How much does one mole of urea molecules
weigh?
Chemical Equations
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Know the basic features of a chemical equation
 Left of the arrow are the reactants
 Right of the arrow are the products
To be interpreted as the number of molecules or
moles that react or are produced
Know how to balance a chemical equation
Know how to use the coefficients in a chemical
reaction to predict the moles of reactants needed or
the moles of products produced
reactants
products
C3 H8 (g) + 5O2 ( g)
3CO2 (g) + 4H2 O( g)
Balance…
Ca( OH) 2 ( s) + HCl( g)
Calcium
hydroxide
CO2 ( g) + H2 O(l)
CaCl2 (s) + H2 O( l)
Calcium
chlorid e
photosynthes is
C6 H1 2 O6 (aq) + O2 (g)
Glucose
C4 H1 0 ( g) + O2 (g)
Butane
CO2 (g) + H2 O(g)
How many moles of N2 are required to
react with 6 moles of H2 to produce NH3
N2 (g) + 3H2 (g)
2NH3 ( g)
Know what reduction and oxidation mean
▪ In a chemical equation, know how to identify the
atom that
1. Was reduced (gained electrons)
2. Was oxidized (lost electrons)
▪ In a chemical equation, know how to identify the
molecule that
1. Was reduced (gained H atoms or Lost O
atoms)
2. Was oxidized (gained O atoms or Lost H
atoms)
Electrons flow
from Zn to Cu
Zn( s)
+
Loses electrons;
is oxidized
Gives electrons
to Cu 2+ ; is the
reducing agent
Gaining and losing electrons
2+
Cu 2 + ( a q)
Gains electrons;
is reduced
Takes electrons
from Zn; is the
oxidizing agent
Zn 2 + ( a q) + Cu( s)
Gaining and losing H and O atoms
Is reduced
CH4 ( g ) + 2 O 2 ( g)
Methane
Is oxidized
CO 2 ( g) + 2 H2 O( g )
Thermochemistry – Heat of the
reaction
▪ Know endothermic and exothermic
mean
exothermic reaction: one that gives
off heat.
endothermic reaction: one that
absorbs heat.
Thermochemistry – Heat of the
reaction
▪ Know how to recognize endothermic
and exothermic reactions
C( s) + O2 (g)
CO2 (g) + 94.0 kcal/mole C
exothermic reaction:
one that gives off
heat.
Avogadro’s number and Molar Mass
▪ Use molar mass and Avogadro’s # to convert
between grams and moles and # of particles
• A tablet of aspirin, C9H8O4, contains 0.360 g of aspirin. How
many molecules of aspirin are present?
– first we find how many mol of aspirin are in 0.360 g.
0.360 g aspirin x
1 mol aspirin
180.0 g aspirin
= 0.00200 mol aspirin
– each mole of aspirin contains 6.02 x 1023 molecules.
– the number of molecules of aspirin in the tablet is
0.00200 mole x 6.02 x 1023 molecules = 1.20 x 1021 molecules
mole