Gen Chem 3-4 Flashcards
3.1. Atomic Mass
Definited as mass of atom in amu?
Atomic Mass Unit
Atomic Mass
or Atomic Weight
3.1. Atomic Mass
Mass equal to 1/12 mass of carbon-12 atom?
1 a.m.u.
3.1. Atomic Mass
When we measure atomic mass of element, we settle for average mass of mixture of what kind of isotopes?
occurence
naturally-occuring
3.1. Atomic Mass
What is the average atomic mass of natural carbon?
Given:
ABUNDANCES
C-12 : 98.90 %
C-13: 1.10 %
ATOMIC MASSES
C-12: 12.00000 amu
C-13: 13.00335 amu
Average Atomic Mass Natural Carbon = (0.9890)(12.0000 amu) + (0.0110)(13.00335 amu) = 12.01 amu
Sum of Products of Abundance and Atomic Mass
3.1. Atomic Mass
Explain why the atomic mass of Fluorine is not an average value like that of carbon?
The amu of an element is based on the average mass of its STABLE, NON-RADIOACTIVE ISOTOPES
3.2. Avogadro’s #; Molar Mass of Elements
The amount of a substance containing as many elementary entities as there are atoms in exactly 12 g of carbon-12 isotope.
Mole
3.2. Avogadro’s #; Molar Mass of Elements
what is NA = 6.022x10^23 atoms?
Avogadro’s number
Actual number of atoms in 12g of C-12
3.2. Avogadro’s #; Molar Mass of Elements
The mass of 1 mole of units of a substance
molar mass
g/mol, kg/mol
3.2. Avogadro’s #; Molar Mass of Elements
How to know mass of single atom in grams?
Formula?
M Single = MM/Avogadro
Mnemonics: Single Marksman (MM) si Avogadro
3.2. Avogadro’s #; Molar Mass of Elements
For Carbon-12
1 g = 6.022x10^23 amu
1 amu = ???
For Carbon-12
1 g = 6.022x10^23 amu
1 amu = 1.661x10^-24 g
Just divide 1 amu by Avogadro’s # to get mass of atom
3.3. Molecular Mass
Sum of atomic mass (a.m.u) in a molecule?
Molecular Mass
3.3. Molecular Mass
What is the chemical name of CAFFEINE?
1, 3, 7 - trimethylxanthine
3.3. Molecular Mass
Since inonic compounds do not contain discrete molecular units (like NaCl), what should be used instead?
Formula mass (FM) in unit amu
3.3. Molecular Mass
3.4. Mass Spectrometer
In mass spectrometry, a ?????? sample is bombarded by stream of ????-?????? ????????
state of matter, energy of subatomic
determine the relative abundance of isotopes
In mass spectrometry, a gaseous sample is bombarded by stream of high-energy electrons
Amount of current generate DIRECTLY PROPORTIONAL to Number of Ions
3.4. Mass Spectrometer
1922 Nobel Prize Physics - developed 1st mass spectrometer
English P.
Francis William Aston
Mnemonics: F.W.A Mass
3.4. Mass Spectrometer
ISO - AM - AB
Neon-20 : 19.99 amu : ? %
Neon-22: 21.99 amu : ? %
Neon-21: 20.99 amu : ? %
AM - Atomic mass, AB - Abundance
ISO - AM - AB
Neon-20 : 19.99 amu : 90.92 %
Neon-22: 21.99 amu : 8.82 %
Neon-21: 20.99 amu : 0.257 %
3.5. Percent Composition of Compounds
Chemical Formula of Ascorbic Acid?
C3H4O3
3.5. Percent Composition of Compounds
Chemical Formula of Chalcopyrite
CuFeS2
3.6. Experimental Determination of Empirical Formulas
In an apparatus used to determine the empirical formula of ethanol under combustion, an absober is used. What is its function?
Absorbers are substances that **retain water and carbon dioxide. **
Ethanol (C2H6O) -> H20 + CO2 (via combustion)
3.7. Chem Rxns & Chem Eqns.
Process in which substance is changed into new substance/s?
Chemical reaction
3.7. Chem Rxns & Chem Eqns.
Chemical symbols to show what happens during a chemical reaction?
3.8. Amount of Reactants and Products
The quantitative study of reactants and products in a chemical reaction?
Stoichiometry
3.8. Amount of Reactants and Products
“The ** stoichiometric coefficients** in a chemical equation can be interpreted as number of moles of each substance…”
What do you call this method?
Mole method
