Review of Grades 9 - 11 Science. Significant Digits 1.Begin counting at the first non-zero digit a)if there is a decimal, count to the last digit Ex:

Review of Grades 9 - 11 Science

Significant Digits

1. Begin counting at the first non-zero digita) if there is a decimal, count to the last digit

Ex: 23.50 mol (4 s.d.) 0.068 mL (2 s.d.)

b) if there is no decimal, count to the last non-zero digitEx: 750 g (2 s.d.)

Significant Digits

2. Numbers with an infinite number of significant digits:

a) Counting Numbers (eg 12 eggs [not 11 or 13] - repeating decimal of 0)

b) Numbers as definitions of equalities (eg 1 L = 1000 mL)

c) Coefficients in a chemical equation

Significant Digits

3. Mathematical Operationsa) Multiplication & DivisionRound off the answer to the least number of significant digits.Ex: 12.8 cm x 5.4 cm = 69 cm2 (2 s.d)

Significant Digits

3. Mathematical Operationsb) Addition & SubtractionRound off the answer to the least number of decimal places.

Ex: 355.84 g – 73.1 g= 282.74 g= 282.7 g

Accuracy in Measurement

Use percentage difference:% Difference = experimental value – predicted value| x

100%predicted value

Significant Digits

Rounding OffPerformed ONLY at the end of a solutionIf discarded digit isa) 0 - 4 the last digit retained is left the sameb) 5 - 9 the last digit retained is increased by one

Nomenclature

• Common ions - page 801• Common multivalent metal ions - page 807• Review: (See next slide)

Nomenclature - What System to use?SYSTEM

FIRST IUPAC COMMON EXAMPLEELEMENT STOCK NONE PREFIX "IC/OUS"

metal(1 oxid #)

Xpotassium chloride

K+(KCl)Mg2+

metal(>1 oxid #)

Xcopper(I)

sulfide

Xcuprous sulfide

Cu+(Cu2S), Cu2+

Fe2+, Fe3+

metalloid(1 oxid #)

X Xsilicon

tetrahydride

Si4+

(SiH4)

metalloid(>1 oxid #)

Xarsenic (III)

fluoride

Xarsenic

trifluoride

As3+(AsF3)As5+

nonmetal Xnitrogen (II)

oxide

Xnitrogen

monoxide

N2+(NO)N3+

N4+,N5+

Nomenclature

• Binary Compoundsuse suffix "ide" (two exceptions for polyatomic "ide" - hydroxide, cyanide)

• Ions with more than 1 oxidation number"ic" higher oxidation number "ous" lower oxidation number- Latin names: ferrum, cuprum, plumbum, aurum, stannum

Nomenclature

• Polyatomic Compounds"ate", "ite", look on the table below the periodic table

Nomenclature - Acids

Binary - use prefix "hydro" (only use of "hydro" in chemistry nomenclature)

Polyatomic - "ate" ion forms an "ic acid"Ex: nitrate NO3

1- and nitric acid HNO3(aq)

- "ite" ion forms an "ous acid"Ex: nitrite NO2

1- and nitrous acid HNO2(aq)

Nomenclature - Acids

Oxy-acid prefixes and suffixesHypo ... ite - 2 less "O" than "ate"

... ite - 1 less "O" than "ate" per ... ate - 1 more "O" than 'ate"

Nomenclature

• Hydrates: water after a compoundEx: CuSO4 . 5H2O copper(II) sulfate pentahydrate

• Diatomic Ions:Hg2

2+ O22-

• Diatomic Elements H2 O2 F2 Br2 I2 N2 Cl2

Humour Break!

• Little Willie was a chemist.Little Willie is no more.For what he thought was H2O

Was H2SO4

• Teacher: What is the formula for water?Student: H, I, J, K, L, M, N, OTeacher: That's not what I taught you.Student: But you said the formula for water

was...H to O.

Ionic Equations

• Use Solubility rules on p.487, 801 & 808orSCH4U data sheets provided

Ionic Equations - Example

For the reaction involving lead (II) nitrate solution and potassium iodide solution a precipitate and a salt solution are produced.

a) Write the balanced chemical equation for this chemical reaction.

b) Write the balanced ionic equation for this chemical reaction. (TIE)

c) Write the balanced net ionic equation for this chemical reaction. (NIE)

Ionic Equations - Example

a) Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)

b) (TIE)Pb2+

(aq) +2NO31-

(aq) +2K1+(aq) +2I1-

(aq)PbI2(s)+2K 1+(aq) + 2NO3

1-(aq)

c) (NIE)Pb2+

(aq)) +2I1-(aq)PbI2(s)

Chemical Bonding

• The difference in electronegativity (ΔEN) can be used to describe the chemical bond as

ionic (EN > 1.7)polar covalent (EN 0.5 - 1.7)nonpolar covalent (EN < 0.5)• In a polar molecule the bond dipoles do NOT

cancel.• Ex: compare H2O, CO2

Chemical Quantities

• Recall: n number of molesm mass(g)M molar mass (g/mol)N number of entitiesNA Avogadro’s number

For solutions

C molar concentration (mol/L)

Summary

• Text Reference: pages 778-780, 806 – 812, 814-815

Humour Break!

• Q: Why do chemists like nitrates so much?A: They're cheaper than day rates.

• Q: Why are chemists great for solving problems? A: They have all the solutions.