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 − → Mg 2+ O + 2e − → O 2−

positive ions + negative ions ionic compound The attraction between positive ions and negative ions is 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 by covalent bonds.

Three kinds of chemical formulae to represent a 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 chemical properties.

Group 1A (alkali metals) form cations with ONE positive charge. Group 2A (alkaline earth metals) form cations with TWO positive charge. Group 7A (halogens) form anions with ONE negative charge. Group 8A (noble gases) usually do not form compounds. Other common ions to remember: Al 3+, Zn 2+, Ag +, Cd 2+, Sc 3+, O 2−, S 2−, P 3−, N 3− 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 roman number)

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 KFPbI 2 Mg 3 N 2 SnO SrBr 2 SnCl 4 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 CuNO 2 Pb(C 2 H 3 O 2 ) 2 NH 4 INaBrO 4

Problems Set 3 Naming of ionic compounds

Review Problem Set 3

1 mol = x particles Unit: g/mol molar mass and Avogadro’s number are exact numbers

CaCl 2 a) Calculate the molar mass of CaCl 2. A sample of CaCl 2 is 2.86 g. b) How many moles of CaCl 2, Ca 2+, and Cl − are in this sample? How many Ca 2+, and Cl − ions are in this sample? c) What is the mass of Ca 2+ in this sample? What is the mass of Cl − in this sample? 1 mol = x particles

Two ways to describe the composition of a compound Chemical formula Mass percent of each element

CaCl 2 Calculate the mass percent of Ca and Cl. Pick exactly 1 mol of compound to calculate mass percent.

What is the mass percent of nitrogen in ammonium nitrate?

NH 4 NO 3

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 begins with a vowel. Binary Covalent Compounds nonmetal-nonmetal Examples: page , 131

H 2 O — water NH 3 — 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 − HClO 3 → H + + ClO 3 − HCl(aq), HClO 3 (aq) dissolved in water = aqueous = aq

Acids Binary acids: H and another element Oxyacids: Anions (oxyanion) contain an element and oxygen HCl → H + + Cl − HClO 3 → H + + ClO 3 −

Binary Acids General formula: H n X m 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), H 2 S(aq)

General formula: H n X m O p Use base name of oxyanion, change ending as follows: change –ate to –ic; change –ite to –ous. Add the word acid Rules: Oxyacids

Use base name of oxyanionchange –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 = x particles Unit: g/mol molar mass and Avogadro’s number are exact numbers

N 2 O 3 sample: 8.56 g a)Calculate the molar mass of N 2 O 3. b)How many moles of N 2 O 3 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 N 2 O 3 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 N 2 O 3 ? 1 mol = x particles

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 following mass percent: % N and % O. What is its chemical formula? Pick exactly 100 g of compound to calculate.

A laboratory analysis of a compound determined the following mass percent: % N and % O. What is its chemical formula? Pick exactly 100 g of compound to calculate. If the molar mass of this compound is g/mol, what is its molecular formula?

A laboratory analysis of aspirin determined the following mass Percent: % C, 4.48 % H and % O. What is its empirical formula? Example 3.18 on page 115 Pick exactly 100 g of compound to calculate. If the molar mass of this compound is g/mol, what is its molecular formula?

1.000 : : = 1: 2.5 : 3 = 10 : 25 : 30 = 2 : 5 : : : = 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 bonds are formed. Atoms are neither created nor destroyed. Mass is conserved. A−B + C−D → A−C + B−D Example: Chemical Equation: Reactants → Products

Each chemical has a certain composition (formula). We must balance each chemical equation. CH 4 + O 2 → CO 2 + H 2 O22

CH 4 + 2O 2 → CO 2 + 2H 2 O

Specify the physical states of the reactants and products s — solid, l — liquid, g — gas, aq — in aqueous solution CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (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

C 2 H 5 OH (l) + O 2 (g) → CO 2 (g) + H 2 O (g) C 6 H 12 O 6 (s) + O 2 (g) → CO 2 (g) + H 2 O (g) Fe 2 S 3 (s) + HCl (aq) → FeCl 3 (aq) + H 2 S (g) NH 3 (g) + O 2 (g) → NO (g) + H 2 O (g)

Problem Set 6