# Formula Mass or Molecular Mass by yurtgc548

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```									Objective:Convert between the moles and grams of a substance.
Catalyst 11/3/10        Please have out homework to check.
Four students conducted an experiment to test how sunlight affects plant growth. They
planted 3 trays of tomatoes and measured the height of plants over a period of 25 days.
Tray 1 was kept in full sunlight for the duration of each day, Tray 2 was kept in sunlight
only half of the day and Tray 3 was kept in sunlight for only 3 hours each day.

1. Which of the following statements is most accurate based on the data in this chart?
A. Sunlight does not affect the growth of tomato plants.
B. Tomato plants will grow more slowly with decreasing amounts of sunlight.
C. Tomato plants grow most rapidly when exposed to less sunlight.
D. There is no correlation between growth rate and amount of sunlight.
2. Assume that one of the factors below had been used in this experiment. Which one
would not have altered the outcome of the experiment?
A. Fertilizer was used on Tray 3.
B. Tray 1 was watered every day, while Trays 2&3 were watered every other day.
C. Each Tray was given different soil.
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D. Each student took turns tending the plants.
Agenda
   Isotopes & atomic mass (10)
   Molar mass (20)
   Mole to mole conversions (15)

Homework: Molar mass and mole to mole
conversion problems

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ISOTOPE
Atoms of the same element
that differ in mass.
(They have the same # of
p+, but different # of N°)
The periodic table has masses with
decimals because it gives the average
atomic mass of all of the isotopes
AVERAGE                              11B

ATOMIC MASS
10B

 Because of isotopes, the mass of a collection of
atoms has an average value.
 Boron is 20%
10B and 80% 11B. That is, 11B is

80 percent of Boron on earth.
 For boron atomic weight

= 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu
Collection Terms
1 trio               =   3 singers

1 six-pack Cola      =   6 cans Cola drink

1 dozen donuts       =   12 donuts

1 gross of pencils   =   144 pencils

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A Moles of Particles

Contains 6.02 x 1023 particles

1 mole C = 6.02 x 1023 C atoms
1 mole H2O= 6.02 x 1023 H2O molecules
1 mole NaCl= 6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions

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Molar Mass
   Number of grams in 1 mole
   Equal to the numerical value of the atomic
mass
1 mole of C atoms         =    12.0 g
1 mole of Mg atoms        =    24.3 g
1 mole of Cu atoms        =    63.5 g
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Learning Check
Give the molar mass to 0.1 g
A. 1 mole of Br atoms          =   ________

B. 1 mole of Sn atoms          =   ________

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Solution
Give the molar mass to 0.1 g
A. 1 mole of Br atoms    =     79.9 g/mole
B. 1 mole of Sn atoms    =     118.7 g/mole

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Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the
sum of the atomic masses
1 mole Ca x 40.1 g/mole + 2 moles Cl x 35.5 g/mole

1 mole of CaCl2       = 111.1 g/mole

2 moles N x 14.0 g/mole + 4 moles O x 16.0 g/mole
1 mole of N2O4 = 74.0 g/mole

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Learning Check

A. 1 mole of K2O               = ______g

B. 1 mole of antacid Al(OH)3   = ______g

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Solution

A. 1 mole of K2O                       = 94.2 g
2 K x 39.1 g/mole + 1 O x 16.0 g/mole

B. 1 mole of antacid Al(OH)3           = 78.0 g
1 Al x 27.0 g/mole + 3 O x 16.0 g/mole
+ 3 x 1.0
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   Just like cookies have
recipes, chemicals have
recipes as well-we call them
chemical equations
   Instead of using cups, we
use moles
   Instead of eggs, butter,
sugar, etc. we use chemical
compounds as ingredients
Chemistry Recipes
   A reaction tells us how much of something you
need to react with something
   Example: 2 Na + Cl2  2 NaCl
   This reaction tells us that by mixing 2 moles of
sodium with 1 mole of chlorine we will get 2
moles of sodium chloride.
   What if we wanted 4 moles of NaCl? 10 moles?
50 moles?
Mole Ratios
   Mole ratios can be used to calculate the moles of one
chemical from the given amount of a different
chemical
   Example: How many moles of chlorine are needed to
react with 5 moles of sodium (without any sodium
left over)?
2 Na + Cl2  2 NaCl

5 mol Na    1 mol Cl2
= 2.5 moles Cl2
2 mol Na
Mole-Mole Conversions
2 Na + Cl2  2 NaCl

   How many moles of sodium chloride will
be produced if you react 2.6 moles of
chlorine gas with an excess (more than
you need) of sodium metal?
Practice
2 H2 + O2  2 H2O
   How many moles of O2 would we need if we
wanted 4 moles of water?
   If we had 3 moles of oxygen, how much
hydrogen would we need to react, and how much
water would we get?
   What if we had 50 moles of hydrogen, how much
oxygen would we need, and how much water
would be produced?

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