What's in the pill?
Empirical and Molecular Formulas
Presentation
Every Compound has 2 formulas
Empirical is:
Molecular Is:
Smallest ratio of atoms in a substance
Actual atoms present in the substance
Example: Formaldehyde
Always able to be reduced!
Example:
Glucose
Acetic Acid Molecular:
Finding Empirical Formula of an unknown chemical
Example: What it the empirical formula for a compound that has 50.5% S and 49.95% O?
1. Change the % to grams
2. Convert grams to moles
3. Divide by the smallest number
4. (If needed) Multiply until you get whole numbers
Author's Name
5. Apply those numbers as subscripts to the elements.
PoeM: An ode to learning how to write empirical formulas
Percent to MassMass to Mole Divide by Small Multiply 'til whole
If you don't end up with a whole number:
Starting with the #2, work your way through the subscripts (multiplying) until you can get all whole numbers.
What is the empirical formula for a compound that is 25.9 % Nitrogen and 74.1 % Oxygen?
A unknown compound containing only phosphorus and oxygen is 56.3% Phosphorous. What is the empirical formula?
Day 2 review problem
Empirical Formula for 15.85 % C and 84.2% S
CS2
Finding the Molecular Formula
1. You need the Emp. Formula
2. You need the molar mass of Mol. Formula
3. Find the molar mass of Emp. Formula
4. Divide Mol. formula mass by Emp. formula mass
5. Multiply # from step 4 by the Emp. Formula subscripts
What is the molecular formula (MF) for a compound that has and empirical formula of NO2 and a molar mass of 138 g.
HO
FInd the molecular formula of a compound using % composition. The molar mass of MF is 147.0 g.
Answer
Emp:C4H5ON2
Mol: C8H10O2N4
Emp: F5S Mol: F10S2
Converting Molecules to Density
The process of converting is: Particles to moles to grams to mL
Will it fit in a pill with a volume of 0.5 mL?
Example: If the density of CO is 0.301 g/mL and the fatal dose of CO is 4.22 x 1020 molecules, (Molar Mass of CO is 27.955 g/mol), will the fatal dose fit into a pill with a volume of 0.9 mL?
Answer: 0.065mL Yes it will fit.
E and M formulas Notes
Ashley Hinton
Created on September 27, 2024
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Transcript
What's in the pill?
Empirical and Molecular Formulas
Presentation
Every Compound has 2 formulas
Empirical is:
Molecular Is:
Smallest ratio of atoms in a substance
Actual atoms present in the substance
Example: Formaldehyde
Always able to be reduced!
Example:
Glucose
Acetic Acid Molecular:
Finding Empirical Formula of an unknown chemical
Example: What it the empirical formula for a compound that has 50.5% S and 49.95% O?
1. Change the % to grams
2. Convert grams to moles
3. Divide by the smallest number
4. (If needed) Multiply until you get whole numbers
Author's Name
5. Apply those numbers as subscripts to the elements.
PoeM: An ode to learning how to write empirical formulas
Percent to MassMass to Mole Divide by Small Multiply 'til whole
If you don't end up with a whole number:
Starting with the #2, work your way through the subscripts (multiplying) until you can get all whole numbers.
What is the empirical formula for a compound that is 25.9 % Nitrogen and 74.1 % Oxygen?
A unknown compound containing only phosphorus and oxygen is 56.3% Phosphorous. What is the empirical formula?
Day 2 review problem
Empirical Formula for 15.85 % C and 84.2% S
CS2
Finding the Molecular Formula
1. You need the Emp. Formula
2. You need the molar mass of Mol. Formula
3. Find the molar mass of Emp. Formula
4. Divide Mol. formula mass by Emp. formula mass
5. Multiply # from step 4 by the Emp. Formula subscripts
What is the molecular formula (MF) for a compound that has and empirical formula of NO2 and a molar mass of 138 g.
HO
FInd the molecular formula of a compound using % composition. The molar mass of MF is 147.0 g.
Answer
Emp:C4H5ON2
Mol: C8H10O2N4
Emp: F5S Mol: F10S2
Converting Molecules to Density
The process of converting is: Particles to moles to grams to mL
Will it fit in a pill with a volume of 0.5 mL?
Example: If the density of CO is 0.301 g/mL and the fatal dose of CO is 4.22 x 1020 molecules, (Molar Mass of CO is 27.955 g/mol), will the fatal dose fit into a pill with a volume of 0.9 mL?
Answer: 0.065mL Yes it will fit.