CHM 121 Chapter Notes - Chapter 3: Empirical Formula, Unified Atomic Mass Unit, Chloroethane
7 Jun 2018
School
Department
Course
Professor
3.1 Representing Chemistry on Different Levels
● 22 02 220
● Microscopic: 2 molecules of hydrogen gas react with 1 molecule of oxygen gas to yield
2 molecules of liquid water
● Macroscopic: 2 moles of hydrogen gas react with 1 mole of oxygen gas to yield 2 moles
of liquid water
3.2 Balancing Chemical Equations
● Balanced: the numbers and kinds of atoms on both sides of the reaction arrow are the
same
● Formula unit: one unit- whether atom, ion, or molecule- corresponding to a given
formula
● 22 222
○ 2 H and 2 O atoms on this side 4 H and 2 O atoms on this side
● 2 22
○ 2 Na and 2 Cl atoms on this side 2 Na and 2 Cl atoms on this side
● 322 223
○ 1 Hg, 2 N, 6 O, 2 K, and 2 I atoms on this side 1 Hg, 2 N, 6 O, 2 K, and 2 I
atoms on this side
3.3 Chemical Arithmetic: Stoichiometry
● Unified atomic mass unit (u): average mass of the element’s atoms
● Molecular weight: average mass of the substance’s molecules
● Formula weight: equals the sum of the atomic weights of all atoms in the molecule
● For ethylene, 24:
○ Atomic weight of 2C= (2)(12.0)= 24.0
○ Atomic weight of 4H= (4)(1.0)= 4.0
○ Molecular weight of 26= 28.0
● For hydrogen chloride, :
○ Atomic weight of H= 1.0
○ Atomic weight of Cl= 35.5
○ Molecular weight of HCl= 36.5
● For ethyl chloride, 25 :
○ Atomic weight of 2C= (2)(12.0)= 24.0
○ Atomic weight of 5H= (5)(1.0)= 5.0
○ Molecular weight of 25= 64.5
● Mole: numerically equal to the element’s atomic weight
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Microscopic: 2 molecules of hydrogen gas react with 1 molecule of oxygen gas to yield. Macroscopic: 2 moles of hydrogen gas react with 1 mole of oxygen gas to yield 2 moles of liquid water. Balanced: the numbers and kinds of atoms on both sides of the reaction arrow are the same formula. Formula unit: one unit- whether atom, ion, or molecule- corresponding to a given. 2 h and 2 o atoms on this side 4 h and 2 o atoms on this side. 2 na and 2 cl atoms on this side 2 na and 2 cl atoms on this side. 1 hg, 2 n, 6 o, 2 k, and 2 i atoms on this side 1 hg, 2 n, 6 o, 2 k, and 2 i atoms on this side. Unified atomic mass unit (u): average mass of the element"s atoms. Molecular weight: average mass of the substance"s molecules.
