chapter 2 elements,compounds,chem equations and calculations

8/15/2019 CHAPTER 2 Elements,Compounds,Chem Equations and Calculations

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CHAPTER 2Elements, Compounds,Chemical Equations and

Calculation


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1. Elements are composed of extremely small particles

called atoms.

2. All atoms of a given element are identical, having the

same size, mass and chemical properties. The atoms ofone element are different from the atoms of all other

elements.

3. Compounds are composed of atoms of more than one

element. n any compound, the ratio of the num!ers of

atoms of any t"o of the elements present is either an

integer or a simple fraction.

#. A chemical reaction involves only the separation,

com!ination, or rearrangement of atoms$ it does not

result in their creation or destruction.


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1. The basic unit of an element that can enter into chemicalcombination.

2. Made up by three particles-electrons, protons, neutrons.

3. (i Electrons ! the ne"ati#ely char"ed particles.

(ii $rotons ! the positi#ely char"ed particles

(iii %eutron ! electrically neutral particles ha#in" a mass

sli"htly "reater than that of protonsProton + neutron

electron

ATOM


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THE STRUCTURE OF THE ATOM

electron


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&tomic %umber (' - %o. of protons in nucleus

%o. of atomic %o. of proton %o. of electron

Mass %umber (&

Mass number %o. of proton ) %o. of neutron

&tomic number (* ) %o. of neutron

Mass number

Atomic number

Atomic Number, Mass Number, and Isotopes


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6 protons, 8 (14 - 6 neutrons, 6 electrons

6 protons, ! (11 - 6 neutrons, 6 electrons

"o# man$ protons, neutrons, and electrons are in %

14

6 &

"o# man$ protons, neutrons, and electrons are in %11

6 &


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Isotopes ! atom that ha#e the same atomic number butdi+erent mass numbers.

Isotope

'ame i))erent

1* No o) proton

* %emical properties

1* No o) neutron

* P$sical properties


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1

1

"$droen

1

euterium

.

1

Tritium

Example / isotopes o) $droen


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1

1

"$droen

1

euterium

.

1

Tritium

Atom

Molecule

Isotope


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Period

0rou

p

Al1ali

Me

ta l

Noble0as

"alo

-en

Al1ali2art,

Me

tal

Te Modern Periodic Table


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1. Molecules ! is an a""re"ate of at least to atoms in adenite arran"ement held to"ether by chemical bonds.

2. & diatomic molecule contains only to atoms.

3. & polyatomic molecule contains more than to atoms

Molecules

H2 H2O NH3 CH4


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3 An ion is an atom, or group of atoms, that hasa net positive or negative charge.

Ions

Cation – ion with a positive charge

If a neutral atom loses one or more electronsit ecomes a cation.

Na11 protons

11 electrons Na+

11 protons

1 electrons

Anion – ion with a negative charge If a neutral atom gains one or more electrons itecomes an anion.

%l15 protons

15 electrons

%l-15 protons

18 electrons


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%emical ormulas

3 Chemists use chemical formulas toepress the composition of molecules

and ionic compounds in terms ofchemical symbols.

3 2 types of formulas/ 7 Molecular formulas

7 Empirical formulas


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M0EC& 40M&1. Molecular formula ! shos the eact no.

of atoms of each element in the smallestunit of substance.

2. &llotrope is one of to or more distinct forms of

an element.Eamples / allotropes of oy"en

02 is oy"en

03

is o*one

3. 5tructural formula shos ho atoms arebonded to one another in a molecule.


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1. Empirical formulas tell us hich elements arepresent and the simplest hole-number ratio oftheir atoms.

2. Empirical formulas are ritten by reducin" thesubscripts in the molecular formulas to thesmallest possible hole numbers.

H2OH2O

Molecular formula Empirical formula

C6H12O6 CH2O

O3 O

N2H4NH2

EM$66C& 40M&


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4ormula of ionic compounds /

(i usually the same as their empirical formulas

(ii eample/ sodium chloride (%aCl consists ofequal no. of %a) and Cl- ions.

60%6C C0M$0%75


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Method of Writing Chemical Formula for Ionic

Compound

!luminium o"ide #containing !l3$ and O2%&

!l3$ O2%

Charge 3$ 2%

'implet ration

of ion com(ined 2 3

'um of charge i 2#$3& $ 3#%2& ) *

'o+ 2 cation !l3$

com(ined ,ith 3 anion O2%

to formaluminium o"ide

Formula- !l2O3


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rite te )ormula o) manesium nitride, containin te M + and N.- ions

Charge 2$ 3%

'implet ration

of ion com(ined 3 2

'um of charge i 3#$2& $ 2#%3& ) *

'o+ 3 cation Mg 2$ com(ined ,ith 2 anion N 3% to

form magneium nitride

Formula- Mg3N2

M + N .-


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Namin %ompounds

1. Elements%

9e)er to te periodic table

2:amples/

i Na ; sodium ii 'i ; silicon


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:. Transition metals can form more than one type of cation.

3 Endin" 8-ous9 to the cation ith feer )#e char"es3 Endin" 8-ic9 to the cation ith more )#e char"es

Eample/ 4e2) ferrous ion 4e3) ferric ion

5o the names of the compounds that these iron ions form ithchlorine ould thus be4eCl2 4errous chloride

4eCl3 4erric chloride

3 5ome metallic elements can assume three or more di+erent )#echar"es in compounds. 5o the char"e on metal is indicate char"eby oman numerals.

Eample/ Man"anese (Mn atoms


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3. Molecular compound

- place the name of the first element in theformula first and second element is named by

adding “-ide” to the root of element name

- Nonmetals or nonmetals + metalloids

- Common names: H2O, NH, CH!

- "lement furthest to the left in a period and

closest to the bottom of a group on periodic

table is placed first in formula

- #f more than one compound can be formed

from the same elements, use prefi$es to

indicate number of each %ind of atom

- &ast element name ends in “-ide”


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/uideline in naming compound

,ith prefi"e

3 0he prefi" mono% ma(e omitted for the firt

element.

3 For o"ide+ the ending a in the prefi" i

ometime omitted.

% for e"ample- N2O4 ma(e called dinitrogen

tetro"ide rather than dinitrogen tetrao"ide.


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"I $droen iodide

N. nitroen tri)luoride

'O sul)ur dio:ide

N%l4 dinitroen tetracloride

NO nitroen dio:ide

NO dinitroen mono:ide

Molecular %ompounds


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3 Eceptions to the use of ;ree<prees are molecular compoundscontainin" hydro"en.

7 Eample / =2>? diborane

C>: methane

5i>: silane %>3 ammonia


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An acid can be de)ined as a su!stance that yields

hydrogen ions &'() "hen dissolved in "ater.

or e:ample/ "%l as and "%l in #ater

3Pure substance (aseous or pure

li>uid state, hydrogen chloride

3issol?ed in #ater (".O+

and %l*

,hydrochloric acid


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' !n oxoacid are acid that contain hdrogen+ o"gen+ and

another element the central element.

i& HNO3 nitric acid

ii& H2CO3 car(onic acid

iii& H3O4 phophoric acid

i5& HCIO3 chloric acid

5& H2'O4 ulfuric acid

5i& HIO3 iodic acid

5ii&HrO3 (romic acid

' E"ample-


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Rules to name the compoun! starting with the o"oaci!s whose names an!with #$ic%,

&. A!!ition of one ' atom/ The acid is called #per..$ic% acid.

;uidline in namin" ooacids

compounds

"%lO4 (percloric acid"%lO. (cloric acid

2. Removal of one ' atom/ The acid is called #$ous% acid.

"NO (nitrous acid"NO. (nitric acid

(. Removal of two ' atoms/ The acid is called #h)po$ous% acid.

"


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The rules for namin" ooanions (anions of

ooacids compounds1* en all te " ions are remo?ed )rom te @-ic acid, te anionBs name ends

#it @-ate

anion %O. (carbonate"%O.-

* en all te " ions are remo?ed )rom te @-ous acid, te anionBs nameends #it @-ite

anion %lO (clorite"%lO.

.* Te names o) anions in #ic one or more but not all te $droen ions

a?e been remo?ed must indicate te number o) " ions present*

or e:ample/

"PO4 di$droen pospate

"PO4 $droen pospate

PO os ate

-

-

.-


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' ! base can (e defined a a u(tance that ield

hdro"ide ion #OH%& ,hen diol5ed in ,ater.

' E"ample-

NaOH odium hdro"ide

7OH potaium hdro"ide

a#OH&2 (arium hdro"ide


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*) !e+nition & atom &2C #weighs% &2 amu

On thi cale-

1H ) 1.**< amu

16O ) 16.** amu

' Atomic mass i the ma of an atom in atomic ma unit #amu&

' One atomic ma unit = a ma e"actl e>ual to one%t,elfth the

ma of one car(on%12 atom.

ATOMIC MASS


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3 0he average atomic mass i the ,eighted a5erage of

all of the naturall occurring iotope of theelement.

!5erage atomic ma of natural car(on

) #*.?


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' 0he mole (mol) i the amount of a u(tance that contain

a man elementar entitie a there are atom in e"actl

12.** gram of 12C

1 mol ) N A ) 6.*22136: " 1*23

!5ogadro num(er # N A )

@oAen ) 12

air ) 2

' 0he Mole #mol&- ! unit to count num(er of particle

AVOGADRO’S NUMBER AND THE

MOLAR MASS


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Molar mass i the ma of 1 mole of in gramatom

1 mole 12C atom ) 6.*22 " 1*23 atom ) 12.** g

1 12C atom ) 12.** amu

1 mole 12C atom ) 12.** g 12C

1 mole lithium atom ) 6.?41 g of 9i

For an element

atomic ma #amu& ) molar ma #gram&


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Ho, man atom are in *.;;1 g of potaium #7& B

1 mol 7 ) 3?.1* g 7

1 mol 7 ) 6.*22 " 1*23 atom 7

E"ample-

No. of mole ) *.;;1 g

3?.1* gmol

) *.*14 mol

No. of atom ) *.*14 mol " 6.*22 " 1*23 atommol

)


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What i the formula ma of Ca3#O4&2 B

1 formula unit of Ca3#O4&2

3 Ca 3 " 4*.*<

2 2 " 3*.?:

< O $ < " 16.**

31*.1< amu

E"ample-


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Percent composition of an element in a compound )

n " molar ma of element

molar ma of compound" 1**D

n i the num(er of mole of the element in 1 mole of

the compound

C2H6O

DC )2 " #12.*1 g&

46.*: g" 1**D ) ;2.14D

DH ) 6 " #1.**< g&46.*: g

" 1**D ) 13.13D

DO )1 " #16.** g&

46.*: g" 1**D ) 34.:3D

;2.14D $ 13.13D $ 34.:3D ) 1**.*D


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9etermination of empirical

formulaElements C H 'Mass (" :B.2 :.AF A:.AB

mol :B.2 "

12.B1"Dmol

3.:B@

:.AF "

1.BBF"Dmol

:.A:

A:.AB "

1?.BB"Dmol

3.:B?

5implest

ratio

3.:B@

3.:B?

1 3

3

:.A:

3.:B?

1.33 3

:

3.:B?

3.:B?

>1 3

3Empirical formula C

3'

#

3


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3 ,a of repreenting the reaction of H2 ,ith O2 to form H2O

' ! proce in ,hich one or more u(tance i changed into oneor more ne, u(tance i a chemical reaction

' ! chemical equation ue chemical m(ol to ho, ,hat happen

during a chemical reaction

reactant product

CHEMICAL REACTIONS AND

CHEMICAL EQUATIONS


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alancing Chemical E>uation


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1. Write the correct formula#& for the reactant on the left

ide and the correct formula#& for the product#& on theright ide of the e>uation.

Ethane react ,ith o"gen to form car(on dio"ide and ,ater

C2H6 $ O2 CO2 $ H2O

2. Change the num(er in front of the formula #coefficients&

to mae the num(er of atom of each element the ame on

(oth ide of the e>uation. @o not change the u(cript.

2C2H6 NO0 C4H12



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3. 'tart ( (alancing thoe element that appear in onl

one reactant and one product.

C2H6 $ O2 CO2 $ H2O tart ,ith C or H (ut not O

2 car(on

on left

1 car(on

on rightmultipl CO2 ( 2

C2H6 $ O2 2CO2 $ H2O

6 hdrogen

on left

2 hdrogen

on rightmultipl H2O ( 3

C2

H6

$ O2

2CO2

$ 3H2

O


l i Ch i l E ti


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4. alance thoe element that appear in t,o or more reactant

or product.

2 o"gen

on left

4 o"gen

#2"2&

C2H6 $ O2 2CO2 $ 3H2O

$ 3 o"gen

#3"1&

multipl O2 (:2

) : o"gen

on right

C2H6 $ O2 2CO2 $ 3H2O:

2

remo5e fraction

multipl (oth ide

( 22C2H6 $ :O2 4CO2 $ 6H2O


l i Ch i l E ti


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;. Chec to mae ure that ou ha5e the ame num(er of

each tpe of atom on (oth ide of the e>uation.

2C2H6 $ :O2 4CO2 $ 6H2O

Geactant roduct

4 C

12 H

14 O

4 C

12 H

14 O

4 C #2 " 2& 4 C12 H #2 " 6& 12 H #6 " 2&

14 O #: " 2& 14 O #4 " 2 $ 6&



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AMOUNTS OF REACTANTS ANDPRODUCTS

' 'toichiometr-

% comparion of coefficient in a (alanced e>uation

% 0he >uantitati5e tud of reactant and product

in a chemical reaction


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1. Write (alanced chemical e>uation

2. Con5ert >uantitie of no,n u(tance into mole

3. Je coefficient in (alanced e>uation to calculate the num(er

of mole of the ought >uantit

4. Con5ert mole of ought >uantit into deired unit

E"ample-


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Methanol (urn in air according to the e>uation

2CH3OH $ 3O2 2CO2 $ 4H2OIf 2*? g of methanol are ued up in the com(ution+ ,hat ma of

,ater i producedB

gram CH3OH mole CH3OH mole H2O gram H2O

molar ma

CH3OH

coefficient

chemical e>uation

molar ma

H2O

p

1& Mole of CH3OH ) 2*? g

32 gmol

) 6.;3 mol


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2& From the e>uation+ 2 mol CH3OH i ued to gi5e 4 mol H2O+ if

,e ha5e 6.;3 mol CH3OH+ ho, man mole that H2O ,illproduceB

2 mol CH3OH ) 4 mol H2O

6.;3 mol CH3OH ) B mol H2O

) 4 mol H2O " 6.;3 mol CH3OH

2 mol CH3OH

) 13.*6 mol H2O

3& Ma of H2O

) mol " molar ma H2O

) 13.*6 mol " 1< gmol

2CH3OH $ 3O2 2CO2 $ 4H2O

I;ITI-?


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2NO $ O2 2NO2

NO i the limiting reagent

O2 i the e"ce reagent

' Geactant ued up firt in the reaction.

' xcess reagents- the reactant

preent in >uantitie greater than

necear to react ,ith the >uantit

of the limiting reagent

I;ITI-?REA?E-T

I;ITI-?


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REA?E-T

In one proce+ 124 g of !l are reacted ,ith 6*1 g of Fe2O3

2!l $ Fe2O3 !l2O3 $ 2Fe

Calculate the ma of !l2O3 formed.

1& Mole of !l

) 124 g

2:.* gmol

) 4.;? mol

2& Mole of Fe2O3

) 6*1 g

16* gmol

) 3.:6 mol

@etermination of limiting reagent and e"ce reagent


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3& @i5ide mole of !l and Fe2O3 ,ith their toichiometric

coefficient

i& !l ii& Fe2O3

) 4.;? mol ) 2.2?; mol ) 3.:6 mol ) 3.:6 mol

2 1

' 0he reagent that ho, the mallet no. of mole i a limiting

reagent+ ,hile another reagent i a e"ce reagent.

' 'o+ !l i a limiting reagent+ ,hile Fe2O3 i a e"ce reagent.


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4& From the e>uation+ 2 mol !l i ued to gi5e 1 mol !l2O3 + if ,e

ha5e 4.;? mol !l+ ho, man mole that !l2O3 ,ill produceB

2 mol !l produce 1 mol !l2O3

4.;? mol !l ) 1mol !l2O3 " 4.;? mol !l

2 mol !l

) 2.2?; mol !l2O3

;& Ma of !l2O3

) mol " molar ma !l2O3 ) 2.2?; mol " 1*2.* gmol

) 234 g


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' !heoretical "ield i the amount of product that ,ouldreult if all the limiting reagent reacted.

' Actual "ield i the amount of product actuall o(tained

from a reaction.

D Kield )

!ctual Kield

0heoretical Kield " 1**D

REACTION YIELD

CONCENTRATION OF SOLUTION


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' 0he concentration of a olution i the amount of olute

preent in a gi5en >uantit of ol5ent or olution.

M ) molarity )mole of olute

liter of olution

1& What ma of 7I i re>uired to mae ;**. m9 of a 2.


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9I@TI'- '9I@TI'- '


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#ilution i the procedure for preparing a le concentrated olution

from a more concentrated olution.

@ilution!dd 'ol5ent

Mole of olute

(efore dilution #i&

Mole of olute

after dilution #f&)

M iLi M f Lf )

9I@TI'- '9I@TI'- '

B'@TI'-BB'@TI'-B

E!M9E-


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E!M9E-

1& Ho, ,ould ou prepare 6*.* m9 of *.2** M HNO3

from a toc olution of 4.** M HNO3B

M 1L1 ) M 2L2

M 1 ) 4.** M M 2 ) *.2** M L2 ) *.*6** 9 L1 ) B 9

L1 ) M 2L2

M 2

)*.2** M " *.*6** 9

4.** M ) *.**3** 9 ) 3.** m9

@ilute 3.** m9 of acid ,ith ,ater to a total 5olume of 6*.* m9.

Concentration @nitsConcentration @nits


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Concentration @nitsConcentration @nits

0he concentration of a olution i the amount of olute preent

in a gi5en >uantit of ol5ent or olution.

ercent ( Ma

D ( ma ) " 1**Dma of olute

ma of olute $ ma of ol5ent

) " 1**Dma of olute

ma of olution

ercent ( Lolume #D55&

D ( 5olume ) " 1**DLolume of olute

Lolume of olution


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M )mole of olute

liter of olution

Molarit (M)

Molalit (m)

m ) mole of olutema of ol5ent #g&

VOLUMETRIC ANALYSIS (VA)


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3 uantitati5e analtical proce (aed on meauring5olume.

3 0he mot common form of L! i the titration+ a proce

,here( a tandard olution of no,n concentration ichemicall reacted ,ith a olution of unno,nconcentration in order to determine the concentrationof the unno,n.

VOLUMETRIC ANALYSIS (VA)

TITRATIONS


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' In a titration a olution of accuratel no,n concentration#tandard olution& i added graduall added to another olution

of unno,n concentration until the chemical reaction (et,een

the t,o olution i complete.

3 quivalence point = the point at ,hich the reaction i complete

' $ndicator = u(tance that change color at #or near& the

e>ui5alence point

TITRATIONS

' 0itration can (e ued in the anali of acid%(ae reaction

H2'O4 $ 2NaOH 2H2O $ Na2'O4


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'lo,l add (ae

to unno,n acid

JN0I9

the indicator

change color

PR'CE9@RE 'R THE TITRATI'-PR'CE9@RE 'R THE TITRATI'-

E!M9E-


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1& What 5olume of a 1.42* M NaOH olution i re>uired to titrate

2;.** m9 of a 4.;* M H2'O4 olutionB

WGI0E 0HE CHEMIC!9 EJ!0ION

H2'O4 $ 2NaOH 2H2O $ Na2'O4

MaLa

M(L(

)a

(

/a concentration of acid/! concentration of !ase

5a volume of acid

5! volume of !ase

a coefficient of acid

! coefficient of !ase

.6 /) &2 m7)

&1.#26 /) &5!)

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chapter 2 elements,compounds,chem equations and calculations

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