Chapter 03B: Molecules, Compounds, and Chemical Equations

Question 1

Molecular mass

Answer 1

Sum of atomic masses (in amu) in a molecule.

Question 2

Formula mass

Answer 2

Sum of the atomic masses (in amu) in a formula unit of an ionic compound

Remember:
formula unit : molecular formula
as
ionic compound : molecular compound

Question 3

Mass percent composition

Answer 3

Mass percent of each element in a compound

mass % = (__n) (molar mass of element) x 100
(molar mass of compound)

Where n = mol of element in compound

E.g. CO₂, n = 2 when calculating mass % of O

Question 4

Calculating empirical formulas

Answer 4

1) % percent –> g –> mol (for each element)

2) Set up unsimplified ratio (framework of empirical formula)
Simplify: divide by the smallest # of mol

3) Change simplified mole ratios to integer subscripts
*If element(s) in ratio are not close to a whole number, multiply the ratio, then round –> empirical formula

Question 5

Combustion analysis

Answer 5

Technique for analyzing compounds, mostly for organic compounds

Uses product mass, reactant composition to determine empirical formula (and eventually molecular formula)

Question 6

Calculating molecular formula from empirical formula

Answer 6

Molecular formula is a multiple of empirical formula

Molecular formula = (empirical formula)_n

Where n = positive integer

n = molar mass
empirical formula molar mass

Question 7

Chemical reaction

Answer 7

Chemical change; 1+ substances are changed into 1+ new substances

Question 8

Chemical equation

Answer 8

Shorthand notion for chemical reactions

Used for:

• displaying reactants & products
• indicating specific amounts of materials used/produced

Question 9

Organic compounds

Answer 9

Mainly made of C and H
Sometimes with O, N, P, S (+ trace amounts of other elements)

Question 10

C in organic compounds (3 details)

Answer 10

1) C bonds almost always covalently
2) Each [starter] C forms 4 bonds somehow:
*4 single, 2 double, 1 triple + 1 single, etc.
*e.g. C₂H₂ and CH₃COOH
3) C can form limitless changes of C atoms (unique)
*straight, branched, and ring-form

Question 11

Organic compounds –> two subcategories (nomenclature)

Answer 11

Organic compounds

Hydrocarbons Functionalized hydrocarbons

Question 12

Hydrocarbons

Answer 12

Organic compounds with ONLY C and H

E.g. common fuels

Question 13

Alkanes

Answer 13

Hydrocarbons with only single bonds

Question 14

Alkenes

Answer 14

Hydrocarbons with double bonds

Question 15

Alkynes

Answer 15

Hydrocarbons with triple bonds