Upload
sybil-chandler
View
218
Download
1
Embed Size (px)
Citation preview
Review Problem Set 2
Experiment 2 Tomorrow
Read the lab manual before coming.
Bring lab manual, data form, and goggles.
Dress properly according to the syllabus.
Aprons not required for this experiment.
Ch 3. Molecules, Compounds, and Chemical Equations
No change occurs inside a nucleus in chemistry
Atoms can lose or gain electrons
Na − e− → Na+ positive ion = cation
Cl + e− → Cl− negative ion = anion
Mg − 2e− → Mg2+
O + 2e− → O2−
positive ions + negative ions
ionic compound
The attraction between positive ions and negative ionsis called ionic bond.
Green: Cl−, Purple: Na+
Atoms can combine together by sharing electrons
Covalent bond
Different elements combined by covalent bonds
Covalent compound
Molecule is a group of atoms held together bycovalent bonds.
Three kinds of chemical formulae to representa covalent compound
Molecular formula
Structural formula
Empirical formula
metals: tend to lose electrons
nonmetals: tend to gain electrons
metal + nonmetal → ionic compound
nonmetal + nonmetal → covalent compound
Row: period Column: group
Elements in the same group have similar chemicalproperties.
Group 1A (alkali metals) form cations with ONE positivecharge.
Group 2A (alkaline earth metals) form cations with TWO positive charge.
Group 7A (halogens) form anions with ONE negativecharge.
Group 8A (noble gases) usually do not form compounds.
Other common ions to remember: Al3+, Zn2+, Ag+, Cd2+, Sc3+, O2−, S2−, P3−, N3−
Remember these properties
How to write chemical formulae for ionic compounds?
1) Write positive ion first, then negative ion. No “+” or “−” in a formula.
2) Subscripts are determined by balancing the charge.
number of positive charge = number of negative charge
3) When subscript is 1, no need to specify.
Binary Ionic Compounds
NOMENCLATURE
two kinds of elements
Ionic Compounds
Naming for Ions
Cations
Type I: fixed charge (remember them)
Type II: different charge
Naming for Ions
Cations
Type I: fixed charge (remember them)
Type II: different charge
Type I: Same name as the metal
Naming for Ions
Cations
Type I: fixed charge (remember them)
Type II: different charge (mostly transition metals)
Naming for Ions
Cations
Type I: fixed charge (remember them)
Type II: different charge (mostly transition metals)
Type I: Same name as the metal
Type II: Same name as the metal (charge in romannumber)
Naming for Ions
Anions: add –ide to element’s base name
Cations: done
Remember them
Naming for Ionic Compounds
Compound name = Cation name + Anion name
Exercises on Page 131
KF PbI2 Mg3N2 SnO
SrBr2 SnCl4 Names → formulae
Calcium sulfide
Lithium nitride
Mercury (II) oxide
Aluminum chloride
Manganese (IV) oxide
Iron (III) oxide
Binary Ionic Compounds
Ionic Compounds with Polyatomic Ions
NOMENCLATURE
Naming for Ionic Compounds
Compound name = Cation name + Anion name
Exercises on Page 131
Ba(OH)2 CuNO2 Pb(C2H3O2)2
NH4I NaBrO4
Problems Set 3
Naming of ionic compounds
Review Problem Set 3
1 mol = 6.022 x 1023 particles
moles
grams in massmassmolar
Unit: g/mol
molar mass and Avogadro’s number are exact numbers
CaCl2
a) Calculate the molar mass of CaCl2.
A sample of CaCl2 is 2.86 g. b) How many moles of CaCl2 , Ca2+, and Cl− are in this sample? How many Ca2+, and Cl− ions are in this sample?
c) What is the mass of Ca2+ in this sample? What is the mass of Cl− in this sample?
1 mol = 6.022 x 1023 particlesmass in grams
molar massmoles
% 100 sample wholeof mass
component of mass percent mass
Two ways to describe the composition of a compound
Chemical formula Mass percent of each element
CaCl2
Calculate the mass percent of Ca and Cl.
Pick exactly 1 mol of compound to calculate mass percent.
% 100 sample wholeof mass
component of mass percent mass
mass in gramsmolar mass
moles
What is the mass percent of nitrogen in ammonium nitrate?
% 100 sample wholeof mass
component of mass percent mass
What is the mass percent of nitrogen in ammonium nitrate?
NH4NO3
% 100 sample wholeof mass
component of mass percent mass
Binary Ionic Compounds
Binary Covalent Compounds
Ionic Compounds with Polyatomic Ions
NOMENCLATURE
Remember these Prefixes
• 1 = mono-
• 2 = di-
• 3 = tri-
• 4 = tetra-
• 5 = penta-
• 6 = hexa-
• 7 = hepta-
• 8 = octa-
• 9 = nona-
• 10 = deca-
1. The first element in the formula is named first, using the element name.
2. The second element is named as if it were an anion.
3. Prefixes are used to denote the number of atoms present.
4. The prefix mono- is never used for naming the first element.
5. Drop the final o or a of the prefix when the element beginswith a vowel.
Binary Covalent Compounds
nonmetal-nonmetal
Examples: page 101-102, 131
H2O — water
NH3 — ammonia
Binary Ionic Compounds
Binary Covalent Compounds
Ionic Compounds with Polyatomic Ions
Acids
NOMENCLATURE
An acid is a compound that releases hydrogen
ions (H+) when dissolved in water.
What is an acid?
HCl → H+ + Cl−
HClO3 → H+ + ClO3−
HCl(aq), HClO3(aq)
dissolved in water = aqueous = aq
Acids
Binary acids: H and another element
Oxyacids: Anions (oxyanion) contain an element and oxygen
HCl → H+ + Cl−
HClO3 → H+ + ClO3−
Binary Acids
General formula: HnXm
Start with prefix: hydro
Use element root name of anion
Add -ic at the end
Add the word acid
Rules:
Example: HF(aq), HCl(aq), HBr(aq), HI(aq), H2S(aq)
General formula: HnXmOp
Use base name of oxyanion, changeending as follows:
change –ate to –ic;change –ite to –ous.
Add the word acid
Rules:
Oxyacids
Use base name of oxyanion change –ate to –ic;change –ite to –ous.
Problems Set 4
Naming of compounds
Matter
Elements
Compounds
Mixtures(multiple components)
Pure Substances(one component)
Homogeneous(visibly indistinguishable)
Heterogeneous (visibly distinguishable)
(Solutions)
Ionic
Covalent
Classification of Matter
1 mol = 6.022 x 1023 particles
moles
grams in massmassmolar
Unit: g/mol
molar mass and Avogadro’s number are exact numbers
N2O3 sample: 8.56 g
a)Calculate the molar mass of N2O3. b)How many moles of N2O3 are in this sample?
c)How many moles of N are in this sample?
d)How many moles of O are in this sample?
e)How many N2O3 molecules are in this sample?
f)How many N atoms are in this sample?
g)How many O atoms are in this sample?
h)What is the mass percent of N in N2O3?
1 mol = 6.022 x 1023 particles
mass in gramsmolar mass
moles
Problem Set 5
Review Problem Sets 4 and 5
Wash and dry your lab apron
Chemical formula Mass percent of each element
Two ways to describe the composition of a compound
% 100 sample wholeof mass
component of mass percent mass
A laboratory analysis of a compound determined the followingmass percent: 30.45 % N and 69.55 % O.
What is its chemical formula?
element of moles
element of grams in masselement of massmolar
Pick exactly 100 g of compound to calculate.
A laboratory analysis of a compound determined the followingmass percent: 30.45 % N and 69.55 % O.
What is its chemical formula?
element of moles
element of grams in masselement of massmolar
Pick exactly 100 g of compound to calculate.
If the molar mass of this compound is 92.02 g/mol, what isits molecular formula?
A laboratory analysis of aspirin determined the following massPercent: 60.00 % C, 4.48 % H and 35.52 % O.
What is its empirical formula?
Example 3.18 on page 115
element of moles
element of grams in masselement of massmolar
Pick exactly 100 g of compound to calculate.
If the molar mass of this compound is 180.154 g/mol, what isits molecular formula?
1.000 : 2.499 : 3.001 = 1: 2.5 : 3 = 10 : 25 : 30 = 2 : 5 : 6
1.000 : 2.002 : 2.998 = 1: 2 : 3
Conversion to simplest integer ratio
1.0 : 2.4 : 3.0 = 10 : 24 : 30 = 5 : 12 : 15
In a chemical reaction,
Old chemical bonds are broken and new chemical bondsare formed.
Atoms are neither created nor destroyed. Mass is conserved.
A−B + C−D → A−C + B−DExample:
Chemical Equation:
Reactants → Products
Each chemical has a certain composition (formula).
We must balance each chemical equation.
CH4 + O2 → CO2 + H2O22
CH4 + 2O2 → CO2 + 2H2O
CH4 + 2O2 → CO2 + 2H2O
Specify the physical states of the reactants and products
s — solid, l — liquid, g — gas, aq — in aqueous solution
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)
How to balance a chemical equation?
1) Start from the most complicated chemical, adjust the coefficients of others.
2) Make all coefficients to simplest integers.Examples
C2H5OH (l) + O2 (g) → CO2 (g) + H2O (g)
C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
Fe2S3 (s) + HCl (aq) → FeCl3 (aq) + H2S (g)
NH3 (g) + O2 (g) → NO (g) + H2O (g)
Problem Set 6