CHEM 6A Lecture Notes - Lecture 5: Cathode Ray Tube, Atomic Orbital, Ernest Rutherford
3 Jun 2018
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Quiz 10/18 next Wed
â—Ź 30 pts total, 25 mins
â—Ź Naming - symbols and names of elements, formulas and names of polyatomic
ions/molecular compounds 18 pts
â—‹ Nitrite vs nitrate, etc
â—Ź Intensive vs extensive properties, classification of matter, physical vs chemical
properties/changes 4 pts
â—Ź Dimensional analysis 4pts
â—Ź Concept of mass %, law of multiple proportions 4 pts
Atomic Mass Unit
â—Ź To define a relative scale
E.g. A compound contains by mass 5.038% H and 94.96% F. Assuming the chemical formula is
HF, find the mass of F relative to H.
â—Ź Assume a 100.00g sample
â—Ź We have 5.038 H and 94.96g F
â—Ź (n atoms of F) * (mass of a F atom) = 94.96g = 18.85
(n atoms of H) * (mass of a H atom) 5.038g
â—Ź Mass of a F atom = 18.85 * (mass of a H atom)
â—‹ As a relative mass
â—Ź We can have a scale for masses (at atomic scale) if we set the mass of a H atom = 1
“unit”
What are the mass percentages of C and O in CO2?
â—Ź Formula mass of CO2 = atomic mass of C + 2 * (atomic mass of O)
â—‹ Formula mass - sum of atomic masses of all atoms in a chemical formula
â—‹ = 12.010 amu + 2 * (15.999 amu)
â—‹ = 44.008 amu
â—Ź Mass % of C = atomic mass of C * 100%
Formula mass
= 12.010 amu * 100% = 27.290%
44.008 amu
â—Ź Mass % O = 2 * 15.999 amu * 100% = 72.710%
44.008 amu
Discharge tube
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CHEM 6A Full Course Notes
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Document Summary
Naming - symbols and names of elements, formulas and names of polyatomic ions/molecular compounds 18 pts. Intensive vs extensive properties, classification of matter, physical vs chemical properties/changes 4 pts. Concept of mass %, law of multiple proportions 4 pts. A compound contains by mass 5. 038% h and 94. 96% f. assuming the chemical formula is. Hf, find the mass of f relative to h. We have 5. 038 h and 94. 96g f (n atoms of f) * (mass of a f atom) = 94. 96g = 18. 85 (n atoms of h) * (mass of a h atom) 5. 038g. Mass of a f atom = 18. 85 * (mass of a h atom) We can have a scale for masses (at atomic scale) if we set the mass of a h atom = 1. Formula mass of co2 = atomic mass of c + 2 * (atomic mass of o) Formula mass - sum of atomic masses of all atoms in a chemical formula.
