Download Honors-Molecular-Formula

1.
The bond in fluorine has a length of 133pm.
a.
b.
c.
d.
Draw the Lewis Structure.
Convert to meters.
Convert to nm.
What is the shape and bond angle?
If you didn’t take the Bonding Test last week…
they are in the testing center.
You have ONE week (1/24)
Or the score becomes a zero!
Get into groups of 3.
Take turns leading the group through the
questions.
Write a list of new vocabulary terms in your CB.
Take 15 minutes to finish the activity.
Find another group that has the same empirical
formula as your Lego molecule. (The match is
worth points!)
When you finish, work on the Formula packet…
you know more than you think you know!
1.
1.
1.
What is the difference between an empirical
formula and a molecular formula?
Do you have questions on the front side of
the activity?
How did you find the total mass of your
compound?
4. How did you calculate the percent
composition of an element in a compound?
Example: What is the percent composition
of each element in sodium sulfate.
4.
Were you able to find the bag containing
empirical and molecular formulas that
match? What can we say about the mass of a
molecular formula compared to that of the
empirical formula?
Example: What is the molecular formula of a
compound with a molar mass of 64.20 g/mol if
the empirical formula is carbon tetrahydride
(methane).
You should be able to do …
Pages 1 and 2- Determine the formula,
calc % comp and answer the questions.
Page 3- If you are having trouble with
these…. Try page 4 (a little easier).
Do the prelab and read the background.
Honestly…. Do we know the formula for zinc
chloride?
So, we really aren’t “determining” the formula
as much as we are “confirming” the formula.
1.
2.
1.
You are going to mass the zinc. When it
undergoes a chemical reaction, will the
mass of Zn change?
What does HCl look like when it is in
aqueous solution?
Discuss the reaction
Zn + HCl

You have about 7 minutes to get into groups
and look at your Mole Review WS to find silly
mistakes.
(Please start looking on the back side!)
The average score on this assignment in
periods 4 and 8 was a “5/10”.
You have a 250.0 g sample of nitrogen
monoxide that undergoes a decomposition
reaction.
a. Determine the percent composition of each
element.
b. What is the mass of nitrogen?
c. What is the mass of oxygen?
Example: A compound has 45.0g of oxygen,
22.6g of sulfur and 32.4g of sodium. What is
the empirical formula.
Remember- the formula compares the number
of MOLES… so we need to look at moles!
Assume 100.g
An oxide of aluminum is formed by the reaction of
4.151g Al with 3.692g of Oxygen. Determine
the empirical formula of the compound.
1
6
I put the balances in the same locations that they
were in on Wed… Why is that important?
Sources of experimental error???
Work on the lab calculations as a group. No lone
rangers… if you are strong, there may be someone
in your group who needs you!
Don’t rely on the smarty party in your group to do
all the calculations… you would be amazed at how
often they get things wrong.
Be sure to read the entire question and
answer all parts of the question!
Look at your zinc chloride lab…
1. Did you do the prelab questions?
2. Do your calculations have the correct
number of significant figures?
3. Did your error analysis answers have
complete sentences?
4. Did you write a conclusion without
personal pronouns?
About 10 minutes
A Hydrate is a compound that contains water.
The chemical state of the water varies…
In ionic compounds
Na2SO4 ·10H2O
Name: Sodium sulfate decahydride
How would we calculate the molar mass!
Is the ionic salt left when all the water has been
driven off a hydrate.
Purpose: To determine the molecular formula
for the sample hydrate.
CuSO4 · __??_ H2O
Equipment available:
Test tubes
Test tube clamp
Bunsen burner
Scale
Hot pad
Scoopula
Hot glove
100 ml beaker.
Matches
Copper (II) Sulfate
hydrate- You can use
0.3g
10 minutes1.
2.
3.
4.
Write a procedure.
Design a data table that
will help you collect all
the data.
Discuss the calculations
you will need to perform
to complete the lab.
What safety concerns do
you have?
Background- Find out more about hydrates and
what is “trapping” or “attracting” the water. (Cite
your resources)
2.
Purpose- If, then, because statement
3.
Procedure- Step by step, clearly written.
4.
Materials List- Complete with correct spelling
5.
Data- Preferably on a table
6.
Analysis- Calculations (can hand write and scan)
7.
Conclusion- What was learned (no personal
pronouns).
8.
Share with each other on Google Docs…
9. Turn it in to me through my website.
1.
Formula/Reaction unit
Let's take a look
Mass of empty test tube
_____g
Mass of test tube and Copper (II) Sulfate
_____g
Mass of Copper (II) Sulfate before heating _____ g
Mass of Copper (II) Sulfate after heating
Mass of water released during heating
_____ g
_____ g
Remember you are finding the ratio of Copper (II) sulfate
molecules to water molecules.
1.
2.
2.
3.
What is the percent composition of water found in sodium sulfide
nonhydride?
Na2S · 9H2O
A 5.0g sample of barium chloride hydrate was heated and only
4.3g of the anhydrous salt remained. What percent water was in
the hydrate?
A 6.7g sample of Na2SO4·H2O is heated. How much anhydrous
salt remains?
A 5.0g sample of Cu(NO3)2 · nH2O is heated and 3.9 g of the
anhydrous salt remains. What is the value for n?
Turn them in!
Combustion reactions usually involve a
hydrocarbon and oxygen as the reactants and
produce carbon dioxide, water and energy.
Write the chemical equation—
If we can measure the amount of
products released in the combustion
reaction… we can figure out the
empirical formula for the hydrocarbon.
What is the empirical formula for the
hydrocarbon that produces:
23.118 g CO2
18.930 g H2O
C? H ?
Consider the formula NaNO3
a. Draw the Lewis structures for Na and
NO3.
b. Label the cation and anion… do you
see why they want to gain and lose
electrons?
c. Name the compound
CH2
2. CH
3. C3H7
4. C2H3
1.
Questions??