Chemistry Reviewer 2nd Quarter

Oxidation State/number (Valence) • positive or negative numbers assigned to elements • combining capacity of an atom • it tells the number of elections that an atom can donate or gain to become stable Criss-cross method • the oxidation number/ charge of one substance becomes the subscript of the other Cations – positive oxidation numbers 2 methods to name cations: • Stock system o Common method which uses Roman numerals to indicate the charges of the ions • Classical system o Uses the root word of the metal and the suffix  -ous – for lower oxidation numbers  -ic – for higher oxidation numbers 2 types of cations: • Monoatomic ions – single atoms • Polyatomic ions – more than one atom Names of Metal Ions with Variable Oxidation Numbers Formula Stock Name Classical Name Cr2+ Chromium (II) ion Chromous ion Cr3+ Chromium (III) ion Chromic ion Co2+ Cobalt (II) ion Cobaltous ion Co3+ Cobalt (III) ion Cobaltic ion Cu1+ Copper (I) ion Cuprous ion Pb2+ Lead (II) ion Plumbous ion Pb4+ Lead (IV) ion Plumbic ion Hg22+ Mercury (I) ion Mercurous ion Hg2+ Mercury (II) ion Mercuric ion Sn2+ Tin (II) ion Stannous ion Sn4+ Tin (IV) ion Stannic ion Fe2+ Iron (II) ion Ferrous ion Fe3+ Iron (III) ion Ferric ion Mn2+ Manganese (II) ion Manganous ion Mn3+ Manganese (III) ion Manganic ion Anions – negative oxidation numbers Naming Anions: • monoatomic nonmetallic anions – dropping the ending of the elements and adding the eding –ide • polyatomic anions containing oxygen (oxyanions) o series of oxyanions that extends to 2 ions  –ate – higher oxygen  – ite – lower oxygen o Series of oxyanions that extends to 4 ions  4 oxygen – prefix : per- ; suffix : -ate  3 oxygen – suffix : -ite  2 oxygen – suffix : -ate  1 oxygen – prefix : hypo- ; suffix : -ite o For polyatomic oxyanions that begin with H, prefixes like hydrogen are used for H and dihydrogen for 2H

Formula H2PO4 C2H3O2 HSO4 HSO3

Common Polyatomic Ions and Their Charges 12Name Formula Dihydrogen HPO4 phosphate Acetate S 2O 3 Hydrogen sulfate SO4 Hydrogen sulfite SO3

Name Hydrogen phosphate Thiosulfate Sulfate Sulfite

ClO3 ClO3 ClO2 ClO

Hydrogen carbonate Chlorate Chlorate Chlorite Hypochlorite

NO3 NO2 MnO4 CNO SCN CN

Nitrate Nitrite Permanganate Cyanate Thiocyanide Cyanide

HCO3

4P2O7 As2O7 SiO4

CO3

Carbonate

Cr2O7 CrO4 O 2O 4 C4H4O6

Dichromate Chromate Oxalate Tartrate 3-

PO4 PO3 AsO4 AsO3 BO3 AlO3

Phosphate Phosphite Arsenate Arsenite Borate Aluminate

Pyrophosphate Pyroarsenate Orthosilicate

Binary compounds – composed of two elements Naming Binary Compounds • Metal and a nonmetal – write the name of the metal, followed by the name of the nonmetal, modified to end in –ide • Binary compounds that contain metals with variable oxidations numbers – copy the classical or stock system of the metal, foloowed by the name of the nonmetal, modified to end in –ide • 2 Nonmetals (Molecular Compound) – write the cation first followed by the anion (place prefixes in naming compounds of nonmetals) Prefixes Used in Naming Binary Compounds of Nonmetals Prefix Meaning Mono 1 Di 2 Tri 3 Tetra 4 Penta 5 Hexa 6 Hepta 7 Octa 8 Nona 9 Deca 10 Ternary Compounds – contain atoms of three different elements Naming Ternary Compounds: • same rules as for binary compounds are followed. The only difference is that the name of the polyatomic ion replaces the name of the anion Acids Binary Acids – compounds containing hydrogen and nonmetal atoms 2 Types of Binary Acids • Pure Compound – same as naming binary compounds (hydrogen fluoride) • Aqueous Solution – named by the prefix hydro- followed by the name of the anion in which it –ide is replaced by –ic acids (hydrofluoric acid) Ternary Acids – compounds containing hydrogen and a polyatomic ion Naming Ternary Acids • Pure Compound – same as naming ternary compounds (hydrogen nitrite) • Aqueous Solution (nitric acid) o the name of the poly atomic ion and any negative prefix is used o The –ate and –ite are dropped and –ic and –ous acids are respectively added Bases - Compounds containing a metal ion and a hydroxide polyatomic ion

Naming Bases • Writing the name of the metal or cation followed by hydroxide Salt – formed when one or more hydrogen ions of an acid react with one or more hydroxide ions of a base 3 Types of Salt • binary compounds of metal cations with nonmetal anions (NaCl – sodium chloride) • Ternary compounds of metal cations or ammonium ions with negative polyatomic ions ((NH4)SO4 – ammonium sulfate , Al3PO4 – Aluminum phosphate) Hydrates – compounds whose formulas contain water molecules (CuSO4 x 5H2O – copper (II) sulfate pentahydrate) Chemical reactions – involve change in one or more substances into new substances with different physical and chemical properties Reactant – a substance that undergoes a chemical reaction Product – the substance that is produced Reactants --> Products Chemical equation – a short way of describing a chemical reaction in which symbols of the elements and the formulas of compounds represent the change Some Symbols Used in Writing Equations cat

Sample Equation : 2H2O2(aq)  O2 + 2H2O(l) Symbol Meaning + Separate two or more formulas Yield(s) or produce(s)  Solid or formation of precipitate (s) or ↓ (l) Liquid Gas or evolution of gas (g) or ↑ (aq) Aqueous

∆

heat

 or  MnO2

Heat is supplied

cat

Catalyst is used as in the sample  or  equation, MnO2 Catalyst – a substance that hastens a reaction without being used up Balancing Chemical Equation Coefficient – a number before the symbol or formula of the substance • by inspection o Write the equation using the correct symbols and formulas o Check that the number of each kind of atom on both sides of the equation is the same. Consider a polyatomic ion as a group of unchanged unit o Balance the equation one element at a time by writing the proper coefficient until the equation is balanced o Check all the coefficients to see that they are all whole numbers and in the lowest ratio. If the coefficients are fractions, multiply all coefficients by the same number to make all the fractions whole number. If the coefficients are divisible by a common factor, divide to obtain the lowest possible ratio • By Redox (Reduction-oxidation) Reaction o Terms  Redox reaction – is a reaction in which election of an atom in a substance are transferred to an atom of another substance. It is composed of two half reactions, namely, oxidation and reduction reactions  Oxidizing Agent – the substance that contains the atom that has gained electrons  Oxidation – is a half- reaction that involves loss of electrons resulting to an increase in the oxidation number  Oxidized – the atom that has lost electrons

 

o

o

Reducing Agent – the substance that carries the atom that has lost electrons Reduction – is a half-reaction that involves gain of electrons resulting to a decrease of oxidation number Reduced – the atom that has gained electrons

 Rules  The oxidation number of a free element (uncombined state) is 0  In a compound, the less electron negative element is given positive oxidation number while the more electron negative element is given negative oxidation number  In the formula of a compound, the sum of the positive and negative oxidation number should be equal to 0  In polyatomic ions, the sum of the oxidation numbers of the atoms present is equal to the charge of the ion  In all oxygen compounds, the oxidation number of oxygen per atom is -2. Exceptions are the peroxides where the oxidation number is -1 and in OF2 where the oxidation number of oxygen is +2  The oxidation number of hydrogen in most of its compounds is +1. when hydrogen combines with metals, its oxidation number is -1  Elements of groups 1A, 2A, and 3A have positive oxidation number equal to their group numbers. The maximum positive oxidation number that can be assigned to an elements is equal to its group number while the maximum negative number assigned to an element is equal to its group number. Some elements have variable oxidation numbers and these are mostly the transition elements Example

Oxidized – Al Reduced – Mn

Oxidizing agent – MnO2 Reducing agent – Al

Types of Chemical Reactions • Combination or synthesis reactions – two or more elements or compounds combine to produce a single product A + B  AB Kinds o metal + oxygen  metallic oxide o nonmetal + oxygen  acidic oxide o metal + nonmetal  salts o metal oxides or basic oxides + water  bases (metallic hydroxides) o nonmetal oxides or acidic oxides + water  acids

•

Decomposition or analysis reactions – a single compound is broken into two or more simple substances AB  A + B Kinds o Oxides  metallic/ acidic oxide + oxygen gas o Carbonates  Carbon oxide + carbon dioxide o Substances decomposed by electricity o Metallic hydroxides  metallic oxides + water o Acids  nonmetallic oxides + water o Metallic chlorates  metallic chlorides + oxygen

•

Single replacement reactions – more chemically active element displaces a substance below it in the activity series A + BC  AC + B Kinds o Replacement of a metal by a more active metal (Zn + CuSO4  Zn SO4 + Cu)

o Replacement of hydrogen in water by metals (Ca + 2H2O  Ca(OH)2 + H2)

o Replacement of hydrogen in acids by metals (Zn + H2SO4  ZnSO4 •

•

+H2) Double replacement or metabolic reactions – involves the exchange of cations and anions between two compounds. Replacement reactions can be written as net ionic equations AB + CD  AD + CB o Terms  Spectator ions – the ions that are not directly involved in the reaction  Net ionic equation – an equation that shows only the particles that actually take part in the reaction Combustion reactions – oxygen is always one of the reactants

Scientific Notation • A way of expressing very large or very small numbers in exponential form using the powers of 10 General formula : N x 10e • Where N is equal or more than 1 but not greater than 10 • Where E is any positive or negative integer Steps • Determine N by moving the decimal point so that I will be placed after the first nonzero digit • Multiply N by 10 raised to exponent “e” where “e” is equal to the number of places the decimal point was moved o “e” is positive if the decimal point was moved to the left o “e” is negative if the decimal point was moved to the right Precision – It tells how close several measurements are to the same value. When this happens, the measurement is said to be precise, but not necessarily accurate Accuracy – it tells how close a measurement is to the true or accepted value. A measurement that is accurate or has a high accuracy is one that is close to the true value Significant Figures • these are digits that show accuracy and uncertaintly in measurements 14 . 6 Accuracy Uncertain Rules • All non zero digits are significant • Zeros in between nonzero digits are significant • Zeros to the right of a decimal point and to the right also of a nonzero digit are significant • Zeros to the right of a decimal point but to the left of a nonzero digit are not significant • When a number ends in zeros, the zeros are not significant unless specifically indicated by a bar line placed above the rightmost, such zeros are significant • Powers of 10 in scientific notation have no effect in the number of significant values Rules in Determining the Sum and Difference • The sum and difference should have the same place value with the least accurate place value o 20.25 + 426.002 – 355 = 91.252 = 91 Multiplication and Division • The product or the quotient should have the same number of significant figure with the factor that has the least number of significant figures (25.0)(0.800)(9.20 x 103)

(200)(0.0050) = 18400 = 20000 Measurement – also a way of comparing two things Standard measurement – measuring device that you use Systems • English/ British – from England, inches, foot, pint, ounce, yard • Metric system – from France, from the unit meter, based other units from unit meter, meter, km, cm, dm, mm, g, kg, mg • International System (SI) – used to express physical quantities in al sciences Quantity Length Mass Time Electrical current Temperature Amount of substance Luminous intensity

SI Base Units Name of Unit Meter Kilogram Second Ampere Kelvin Mole Candela

Symbol M Kg S A K Mol cd

Common Prefixes Used with SI Units Prefi Symb Meaning x ol Tera T 1012 Giga G 109 Meg M 106 a Kilo K 103 Hect H 102 o Deca Da 101 Deci d 10-1 Cent c 10-2 i Milli m 10-3 Micr 10-6 μ o Nan 10-9 n o Pico 10-12 p Conversion Factor – a fraction that is equal to one and is used to convert one unit to another Derived Quantities – quantities whose definitions and unites are taken from the fundamental quantities Equipments used in measuring • Spring balance – an instrument used to measure force • Hygrometer – a device for measuring the relative humidity of air • Vernier caliper – can be used to measure the outer and inner diameter • Aneroid barometer – an instrument for measuring atmospheric pressure • Speedometer – shows the speed of a vehicle