Review Problem Set 2. Experiment 2 Tomorrow Read the lab manual before coming. Bring lab manual,...

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 II: different charge

Type I: Same name as the metal

Naming for Ions

Cations


Type II: different charge (mostly transition metals)

Naming for Ions

Cations


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


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.



mass in gramsmolar mass

moles

What is the mass percent of nitrogen in ammonium nitrate?



What is the mass percent of nitrogen in ammonium nitrate?

NH4NO3




Binary Covalent Compounds


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.


nonmetal-nonmetal

Examples: page 101-102, 131

H2O — water

NH3 — ammonia




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


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?


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



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



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



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

Review Problem Set 2. Experiment 2 Tomorrow Read the lab manual before coming. Bring lab manual,...

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