Avagadro & Mass
How many moles are there in 1.3x1020 molecules of NaCl?
0.0022 moles
1.1 mol
What does % composition mean?
% composition is the relative mass of each element in a compound
What differentiates an empirical formula from a molecular one for a particular compound?
(Excluding "boths" such as water)
An empirical formula is the simplest possible version of a chemical formula (fully reduced form)
Is the pressure higher on Mount Everest, or 50km under the ocean?
50km under the ocean
What is the molar mass of CH3COOH? (Acetic acid)
60.0g/mol
What volume does 5.43 mol of CO2 gas take up at 17° C and 100.0kPa? (R = 8.314LkPa/Kmol)
130L (that's almost 33 milk jugs!)
Which element has the highest percent composition in this compound?
FeCl3
Chlorine
Why do we need to find the empirical formula before we find the molecular formula?
We need the empirical formula "skeleton" to know a baseline ratio of each element
(i.e CH2O, we need to know 1C:2H:1O to scale up properly)
Which chemical analysis technique blasts apart a chemical sample with an electron beam creating smaller ion fragments?
Hint: It helps us determine the molar mass of an unknown compound
Mass Spectrometry
138g
Daily Double!
If I have 3.20 mol of a gas in a container with a volume of 30.00L and a pressure of 101.2kPa, what temperature must the gas be in Celsius?
(R = 8.314LkPa/Kmol)
-143° C
What is the percent composition of CO2?
C = 27.3%
O = 72.7%A compound was found to be 53% Al and 47% O. Find it's empirical formula.
Al2O3
Which chemical that is highly reactive in water is also found in many batteries?
Lithium
How many molecules are there in 2.00 mol of calcium hydroxide?
1.20x1024 molecules
What pressure (in kPa) is 2.00mol of argon gas at 35°C in a container with a volume of 55.0L?
(R = 8.314LkPa/Kmol)
p = 93kPa
What is the percent composition of NH4Cl?
N = 26.2%
H = 7.48%
Cl = 66.4%
Daily Double!!
Find the empirical formula for a compound with 1.90% H, 67.6% Cl, and 30.5% O
HClO
The second woman to win a Nobel prize in chemistry played a big part in the early research in radioactivity. Unfortunately, she also died because of radiation poisoning. What was her name?
Marie Curie
How many molecules are there in 56.7g of KClO4 ?
2.46x1023 molecules
How many molecules are there in 40L of a gas at STP conditions?
1 x 1024 molecules
What is the % composition of the bolded species?
Cu(SO4)2 * 5H2O
% H2O = 7.21%
(Answers may vary slightly, I used a compound molar mass of 249.685g/mol)
Find the molecular formula from the given data:
Percent Composition: 65.45% C, 5.45% H, 29.10% O
molar mass of molecular compound = 110g/mol
C6H6O2
On the periodic table, Francium is named for the country of France. Less obviously, what metallic element gets its name from the old Latin name for what is now France?
Gallium
(What is France now used to be called Gaul)