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Transcript
Empirical Formula Lab
Empirical: based on evidence
Empirical Formula: simplest whole-number combination of elements in that
compound
Molecular Formula: actual whole-number ratio between the elements in that
compound (real thing)
Both represent the same compound
C6H12O6
CH2O
Molecular formula
Empirical formula
So what are we trying to do?
By figuring out how much zinc and chlorine are in our product (zinc chloride), we
hope to determine the molar ratio between the two elements
Things we need…..
• Mass of Zn in product
-we will assume ALL of the zinc we had at the
beginning successfully reacted so the amount of
zinc in our product should be the same as the
amount of zinc we started with
• Mass of product
-we don’t want to scrape out the product
Because the amount of
because we don’t want to leave any product
particles in a mole is the same behind. Because of this, we will need the mass
of the beaker alone and subtract is from the
for Cl and Zn, we should be
beaker + product mass
able to use this ratio to
• Mass of chlorine in product
determine the simplest ratio
-if we know the mass of the product & the mass
of Cl to Zn in our compound of of zinc in product, then we should be able to
subtract the mass of zinc from the mass of
zinc chloride
product to get the mass of chlorine
𝑚𝑜𝑙 𝐶𝑙
𝑚𝑜𝑙 𝑍𝑛
Zinc begins to react with hydrochloric acid
(HCl)
• Inside the bubbles is hydrogen gas (H2)
Zn and HCl are placed on a hot
plate to speed up the reaction
When the reaction is
complete and there is
no more HCl left
• What remains is your
zinc chloride product
• Zinc chloride has a
special property that
allows it to “take in”
water from the air so
it’s constantly
“soupy”
• We don’t want this
water involved in our
product…
In order to remove
excess water, we boil it
off
• Being very careful
not to burn our
product!!!
Determine the molecular formula
The empirical formula of a compound is NO2. Its molecular
weight is 92 g/mol. What is its molecular formula?
The empirical formula of a compound is CH2. Its molecular
weight is 70 g/mol. What is its molecular formula?
Using % composition to determine
empirical formula
Find the empirical formula for a compound consisting of 63%
Mn and 37% O
Determining the molecular formula
Determine the molecular formula of a compound that contains
40% C, 6.72% H, and 53.29% O
• Molecular weight of this compound is 180 g/mol
A compound is found to contain 40% carbon, 6.7% hydrogen, and
53.5% oxygen. Its molecular weight is 60 g/mol. What is its
molecular formula?
NutraSweet has the following chemical
composition Carbon: 57.14%
Calculate the empirical formula of NutraSweet and find
the molecular formula
• The molecular weight of NutraSweet is 294.3 g/mol
Hydrogen: 6.16%
Nitrogen: 9.52%
Oxygen: 27.18%
Complete the following problem
After performing an experiment involving the reaction between calcium and bromine,
a lab group recorded the following data.
Mass of calcium (g)
Mass of product CaxBry
1.6
8
Using this data, determine the empirical formula of the compound between calcium and
bromine