Chemistry : Notes Form 4

8/9/2019 Chemistry : Notes Form 4

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Chemistry and Its Importance

Chemistry – earlier study of alchemy (an art

of transforming common metals to precious

metals, usually lead to gold but to no success)

(alchemy has since been proven to be a

wrong and currently dead branch of science)

Chemistry – is the study of

the composition, structure, properties and int

eractions of matter.

Founder of Modern Chemistry (try and

read up on the history of these two great

men)

1. Robert Boyle (1627-1691) –

performed controlled eperiments and

published his !or" !ith elaborate details

such as procedure, apparatus and

obser#ations.

2. Antoine Lavoisier (17$%-179$) –

de#eloped the &a! of 'onser#ation of

ass and thetheory of combustion.

Scientific Method

1. a"ing bser#ation

2. a"ing *nference (smart guess)

%. *dentifying the +roblem

$. a"ing a ypothesis

. *dentifying the ariables

6. 'ontrolling the ariables

7. +lanning an /periment

0. 'ollecting ata9. *nterpreting ata

1. a"ing a 'onclusion

11. 3riting a 4eport

SM Form ! " #erminolo$y and

Concepts% #he Structure of the Atom

Important #erms

Matter – anything that occupies space and

has mass.

Compound – a substance

consists t!o or more elements that

are chemically bonded (molecule or ions).&lement – a substance that cannot be made

into anything simpler by chemical reaction.

Atom – smallest particle of an element.

Molecule – a group of t!o or more atoms.

Ion –

a positi#ely charged 5 negati#ely charged

particle.

Cations – positi#ely-charge ions. /ample

, 8 , $ and g2

Anions – negati#ely-charge ions. /ample

:r-, -, 2- and ;2%2-

'elocity of the particle increases !hen

ing 5 ;olidification – li?uid -@

solid

2. elting – solid -@ li?uid

%. /#aporation – li?uid -@ gas 5 #apour

$. 'ondensation – gas 5 #apour -@ li?uid

. ;ublimation – gas 5 #apour -@ solid

6. ;ublimation – solid -@ gas 5 #apour

( Sublimation – iodine, ammonium chloride

and solid carbon dioxide)

Important Scientist and #heir

Contributions

:erry :erry


2/28

1. Atoms – consists of a positi#ely-

charged nucleus !ith a cloud of electrons

surrounding nucleus.

2. +rotons – positi#ely-charged particles.

0iels Bohr (*.*1)

1. /lectrons – surrounding the nucleus

(orbit).

ames Cad2ic3 (*.14)

1. eutrons – electrically neutral

subatomic particles.

2. eutrons – mass almost the same !ith

a proton.

%. ucleus of an atom – consists of

protons and neutrons.

Concepts of the Atomic Model

Modern Atomic Model

1. ucleus of an atom – consists

of protons and neutrons.

2. /lectrons – mo#ing around

the nucleus (orbits 5 electron shells5

?uantum shells)

roton number 5 Atomic number 5

0umber of protons

1. umber of protons in its atom.

2. umber of electrons (neutral atom).

0ucleon number 5 Mass number 5

0umber of nucleon1. ;um of the number protons and

neutrons.

Isotopes – atoms of the same element

!ith same proton number but different

nucleonnumbers.

SM Form ! " #erminolo$y and

Concepts% Chemical Formulae and

&6uations " art *

1. Relative atomic mass, Ar is the atomic

mass of an atom !hen compared toa standard atom

2. Standard atom

7ydro$en scale hydrogen is the lightest

atom of all and the mass of one hydrogen

atom !as assigned 1 unit.

3ea"ness of ydrogen scale

not too many elements can

react readily !ith hydrogen,

the reacti#e masses of some elements

!ere not accurate,

hydrogen eists as a gas at room

temperature and has a number of isotopes !ith

different masses.

7elium scale the second lightest atom of all

and the mass of one helium atom !as

assigned 1 unit.

3ea"ness of elium scale

ass of 1 helium atom B $ times the

mass of a hydrogen atom

;o, mass of 1 helium atom B $ times

1512 mass of a carbon atom helium eists as a gas at room

temperature and

helium is an inert gas.

89y$en scale chose as the standard atom to

compare the masses of atoms

3ea"ness of ygen scale

the eistence of three isotopes of

oygen !ere disco#ered,

natural oygen (containing all thethree isotopes) as the standard ('hemist)

and

used the isotopes oygen-16 as the

standard (+hysicists).

Carbon scale standard atom of

comparison internationally.

a carbon-12 atom is 12 times

hea#ier than an atom of hydrogen,

used as the reference standard in mass

spectrometers,

eists as a solid at room temperature, most abundant carbon isotope,

happening about 90.09C and

carbon-12 is close to the agreement

based on oygen.

%. Relative molecular mass, Mr of a

substances is the a#erage mass of

a molecule (t!o or more atoms) of the


3/28

substances !hen compared 1512 !ith of the

mass of a carbon-12 atom.

$. Relative formula mass: Fr is

for ionic compound !hich is calculated by

adding up therelati#e atomic masses of all the

atoms.

. &9ample

4elati#e atomic mass, Ar of helium B $

4elati#e molecular mass, r of '2 B

12 2(16) B $$

4elati#e formula mass, =r of a'l B

2% %. B 0.

4elati#e formula mass, a2'%D12

B 2(2%) 12 %(16) 1 E2(1) 16F B 206

*talian physicist Amedeo Avogadro (ame

at birth &oren>o 4omano Amedeo 'arlo

A#ogadro) Born% 9 August 1776

Birthplace%


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moles of atoms of each element in a

compound.

2. olecular formula B (empirical formula)nn is a positi#e number

'ompound olecular formula n /mpirical formula

'arbon dioide '2 1 ('/thane '% 2 ('

+ropene '2 % ('

Llucose '2 6 ('

Muinine '112 2 '

%. 'hemical formulae for co#alent compounds.

ame 'hemical

formula

umber of each element

itrogen gas 2 2 nitrogen atoms

ygen gas 2 2 oygen atoms Ammonia % 1 nitrogen atom and %

hydrogen atoms

3ater 2 2 hydrogen atoms and 1

oygen atom

$. 'ations are positi#ely-charged ions.

'harge 'ations =ormula

1 Ammonium ion $

1 N 'opper(*) ion 'u

1 ydrogen ion

1 &ithium ion &i

1 N ic"el(*) ion i

1 +otassium ion 8

1 ;il#er ion Ag

1 ;odium ion a

2 :arium ion :a2

2 'alcium ion 'a2

2 N 'opper(**) ion 'u2

2 N *ron(**) ion =e2

2 N &ead(**) ion +b2

2 agnesium ion g2

2 N anganese(**) ion n2

2 ic"el(**) ion i2

2 N


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ono- 1

i- 2


6/28

eedelee#Hs +eriodic


7/28

+oor conductors of heat

elting point and boiling point

increases (going do!n the group) –

atomic si>e increases and force of

attraction bet!een atoms of each element

become stronger ensity of element increases (going

do!n the group)

'hemical properties

'hemically inert 5 not reacti#e 5 non-

flammable – do not gain, lose or share

electrons !ith other elements

Pses

elium – airships, !eather balloons,

cool do!n metals

eon – ad#ertising light bulb

Argon – !elding, filled light bulbs

8rypton – used in laser, filled

photographic flash lamps

4adon – treat cancer

(#ips Please follow the safety precaution

prescribed by your teacher in handling the

alkali metals "if you were given the chance to

do so#. The reason is simple, as you will only

need to see the volatile nature of alkali metals

here when they are in contact with water,

!rainiacs video on $lkali %etal &view here'.

$fter viewing the video, you should have noreasons to not follow the safety precautions#

(Second #ips Do try your best to memorise

the elements down the group. (ead aloud

everyday a few times) &ithium, ;odium,

+otassium, 4ubidium, 'aesium and

=rancium. *f you do so, youll memorise it

without much effort. Thatll be an advantage

in exams.#

SM Chemistry Form ! 0otes "

eriodic #able of &lements (art 1)

Alkali metal atom arrangement

=roup * elements

Lroup 1 elements are "no!n as al"ali

metals

Atomic radius (atomic si>e)

– increases (going do!n the group)


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atomic si>e increases and number of shells

occupied !ith electrons increases 5

metallic bonding bet!een atoms becomes

!ea"er Q less heat energy is re?uired to

o#ercome the !ea"er metallic bonding.

&o! density (&i, a and 8 float on the

surface !ater 5 4b, 's and =r sin" in the

!ater)

ensity of element increases (going

do!n the group)

'hemical properties

'hemically #ery reacti#e and react

rapidly !ith oygen and !ater #apour in

the air (must be "ept in paraffin oil)

4eacti#ity increases (do!n the group)

– ho! easily it can lose one (single)

its #alence electronto achie#e stable (octetor duplet) electron arrangement

4eact #igorously !ith cold !ater –

produce al"aline metal hydroide

solutions and hydrogen gas

4eact !ith oygen – produce !hite

solid metal oides and metal oides can

dissol#e in !ater to form al"aline metal

hydroide solutions

4eact !ith halogens – produce !hite

solid metal halides

;afety precautions 'annot hold !ith bare hands

3ear safety goggles and glo#es

o flammable substance nearby

A#oid the fire

(#ips +ou should draw out the diatomic

molecules and their electron configurations

so that you can better understand why they

typically exist in the form of diatomic

molecules. Try to also memorise the atomic

sie as they go down a group. -ote whether if

it is metallic or nonmetallic. /ow abouttheir oxidising abilities0 *f you can answer

those and beyond, you would have mastered

the basic knowledge on halogens.#


eriodic #able of &lements (art !)

Molecules of Halogen

=roup */ elements

Lroup 17 elements are "no!n

as halogens

/ist as diatomic molecules (=2, 'l2,

:r2, *2 and At2)

on-metals

Atomic radius (atomic si>e)

– increases (going do!n the group)


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elting point and boiling point

increases (going do!n the group) –

molecular si>e increases 5 forces of

attraction bet!een molecules become

stronger Q more heat energy is re?uired to

o#ercome the stronger forces of attraction(an der 3aalsH forces of attraction

bet!een molecules).

'olour =2 (pale yello2 $as),

'l2 ($reenish>yello2 $as),

:r2 (reddish>bro2n li6uid),

*2 (purplish>blac3 solid) and

At2 ( blac3 solid – rarest naturally

occurring element and etremely

radioacti#e)

&o! density

ensity of element increases (goingdo!n the group) – increase in atomic

mass

'hemical properties

'hemically reacti#e

4eacti#ity decreases (do!n the group)

– ho! easily it can gain one (single)

more #alenceelectron to achie#e

stable (octet) electron arrangement

4eact !ith !ater – produce t!o acids

4eact !ith hot iron – produce bro!n

solids iron(***) halides 4eact !ith sodium hydroide a

solution – produce !ater and t!o types of

sodium salts (sodium halide and sodium

halite(*))

;afety precautions

+oisonous gas

3ear safety goggles and glo#es

andle in the fume cupboard


eriodic #able of &lements (art ?)

Elements: Zinc Copper Lead Magnesium

&lements in a period


10/28

a, g, Al (metals) good conductor 5

;i (semi-metal) !ea" conductor of

electricity 5 +, ;, 'l (non-metals) cannot

conduct electricity

a, g (metals) form oides !ith

basic properties Al (metal) form oides !ith both

basic and acidic properties B amphoteric

oides

;i (semi-metal) forms oides !ith

acidic properties

+, ;, 'l (non-metals) forms oides

!ith acidic properties

Pses of semi-metals (metalloids)

;emiconductor (flo! in one direction)

icrochip

inc !ith dilute sulphuric acid to liberatehydrogen gas, man$anese(I') o9ide –

decomposition of hydrogen peroide to

liberate oygen gas, iron – aber

process, vanadium(') o9ide – 'ontact

process, platinum – st!ald process)


11/28

=orm comple ions (bigger-si>ed

polyatomic ion) (eacyanoferrate(***)

ion 5 E=e(')6F%- )

Pses

*ron – used as steel

'hromium – coating corroded metals,heat-resisting alloys and ma"e stainless

steel

'opper – ma"ing cables, pipes and

electrical !ires


12/28

Metal 0on>metal –@ Ionic compound

;odium bromine –@ ;odium bromide

'alcium chlorine –@ 'alcium chloride

&ithium oygen –@ &ithium oide

Aluminium nitrogen –@ Aluminium nitride

MetalsLroup 1

A lithium atom !ith an electron

arrangement of 2.1 achie#es stability after

it donates one #alence electron to form a

lithium ion, &i.


13/28

of the fluoride ion, = -, is 2.0 !ith stable

octet electron arrangement.

A chlorine atom !ith an electron

arrangement of 2.0.7 achie#es stability

after it accepts one #alence electron to

form a chloride ion, 'l

-

.


14/28

Covalent Bonds

*t is a chemical bond formed from

the sharing of #alence electrons bet!een

non-metal atoms to achie#e the stable

duplet of octet electron arrangement.

/ach shared pair of electrons isas one co#alent bond.

*t produces molecules.

Psually the co#alent bonds form

bet!een non-metal atoms from Lroup 1,

16 and 17 and sometimes can be formed

from Lroup 1$ (carbon and silicon) and

hydrogen.

'o#alent bond can be formed from

atoms of the same element and atoms of

different elements.

/ample

0on>metal 0on>metal –@ Covalent compound

:romine bromine –@ :romine (:r2)

itrogen nitrogen –@ itrogen (2)

'arbon chlorine –@


15/28

of the follo!ing is the formula of the

compound formed bet!een O and RK

(A) R $O

(B) R 2O

(C) RO() RO2;olution

O has 6 #alence electrons, it needs to

share 2 electrons to achie#e the stable


R has $ #alence electrons, it needs to

share $ electrons to achie#e the stable



16/28

1ovalent 1ompound

'o#alent 'ompound – co#alent bonding is

strong bonding bet!een the atoms in the

molecule

Ionic Compound ifferences Covalent Compound

*ons articles olecules

&ost or gained &lectron ;hared

;trong electrostatics

forces (*onic bond)

bet!een theoppositely-charged

ions arranged in a

%- giant crystal

lattice

Forces ;trong ('o#alent bond)

bet!een the atoms in the

molecule. 3ea" forces ofattraction bet!een the

molecules (#an der 3aalsH

forces)

;olid State Lases or #olatile li?uids

igh Meltin$ point &o! (;imple molecules)igh

(Liant molecules)

igh Meltin$ point &o! (;imple molecules)igh

(Liant molecules)

on-#olatile 'olatility ery #olatile (;imple

molecules)on-#olatile (Liant

molecules)

issol#e in !ater

and polar sol#ents

Solubility in

2ater

o not dissol#e in !ater

o not dissol#e in

organic sol#ent

Solubility in

or$anic solvent

issol#e in organic sol#ent

(ether, alcohol, ben>ene,

tetrachloromethane and

propanone)

'onduct electricity

in li?uid and

a?ueous solution

(positi#e and

negati#e ions canmo#e freely).

'annot conduct

electricity in solid

state (fied position

and cannot mo#e

freely).

&lectricity

conductor

'annot cond

any state (no

ses of covalent compounds as solvent

/ther – sol#ents in the etraction of

chemicals from a?ueous solution

Alcohol – sol#ents used to ma"e in"

and dye because these sol#ent are #olatile


17/28

/ample for electrolytes (al"alis, acids, salt

solution or molten salt)

molten lead(**) chloride

copper(**) sulphate solution

solution containing ions such ashydrochloride acid

0on>electrolyte

on-electrolytes are molecules

that cannot conduct electricity and !ill

not undergo any chemical changes.

*t cannot conduct electricity due to

the absent of free mo#ing ions.

/ample of non-electrolytes (co#alent

substances)

molten acetone

molten naphthalene

glucose solution

Conductor

'onductors are substances that can

conduct electricity in solid or molten state

but do not undergo any chemical changes.

*t can conduct electricity due to

the flo! of electrons.

/ample of conductor

iron

graphite

mercury

Ionic Compounds

Solid state Molten state or a6ueous

state (dissolved in 2ater)

o not conduct electricity 'an conduct electricity

*ons are held in a lattice -

*ons do not mo#e freely *ons are free to mo#e

Covalent CompoundsSolid state Molten state or a6ueous

state (dissolved in 2ater)

o not conduct electricity o not conduct electricity

/ist in molecules /ist in molecules

olecules do not ha#e free

mo#ing ions

/ception 'l and

as free mo#ing ions in !ater


18/28

Inert

electrodes

/lectrodes that do not ta"e

part in chemical reactions

during electrolysis

'arbon or

platinum

Active

electrodes

/lectrodes that ta"e part in

chemical reactions during

electrolysis

'opper or >inc

/ample 1

olten magnesium oide, g

*ons agnesium ions (g2) Q oide

ions (2-)

'athode (egati#e electrode)

g2 mo#e to the cathode

Anode (+ositi#e electrode) 2- mo#e

to the anode

/lectrons flo! from anode to the

cathode through the !ire

'an conduct electricity

/ample 2

olten lead(**) bromide, +b:r2

*ons &ead(**) ions (+b2) Q bromide

ions (:r - )

'athode (egati#e electrode)

+b2 mo#e to the cathode

Anode (+ositi#e electrode) :r - mo#e

to the anode

/lectrons flo! from anode to thecathode through the !ire

'an conduct electricity

/ample %

olten naphthalene

*ons o ions present (naphthalene is

co#alent compound !hich consists of

molecules B uncharged particles)

o electrons flo!s

'annot conduct electricity


19/28

Anode (positi#e electrode) - mo#e

to the anode (ions are selecti#ely

discharge)

/ample 2

.1 mol dm% of copper(**) sulphate,

'u;$ solution +ositi#e ions (cations) copper ions

('u2) and hydrogen ions (),

egati#e ions (anions) sulphate ions

(;$2-) and hydroide ions (-)

'athode (negati#e electrode)

'u2 mo#e to the cathode (ions are

selecti#ely discharge)



discharge)


20/28

+ositi#e ions (cations) copper ions

('u2) and hydrogen ions (),

egati#e ions (anions) sulphate ions

(;$2-) and hydroide ions (-)

'athode (negati#e electrode)

'u2

mo#e to the cathode (ions areselecti#ely discharge). A bro!n deposited

on the cathode.



discharge). Las bubbles are produced. A

colourless gas liberates and it ignites the

glo!ing !ooden splinter.


21/28

*mportance of electroplating is to

pre#ent corrosion and impro#e the

appearance.

'athode obTect to be electroplated

Anode pure plating metal

/lectrolyte a?ueous solution containsplating metal ions

'oltaic Cell 5 =alvanic cell

*t is an electrochemical cell !hich con#erts

chemical energy –@ electrical energy

egati#e terminal more

electropositi#e (higher position in the

electrochemical series)

+ositi#e terminal less electropositi#e

(lo!er position in the electrochemical

series) /lectrons released (more

electropositi#e metal) through the !ire to

a less electropositi#e metal.

/ample 1 Iinc plate and iron plate are

placed in 1. mol dm% of lead(**) nitrate,

+b(%)2solution

egati#e terminal (Anode) Iinc metal

(Iinc plate dissol#es to form In2)

+ositi#e terminal ('athode) *ron

metal (hydrogen ions !ill be selecti#ely

discharge to form hydrogen gas. *t is

because is lo!er position than +b2 and

In2 in the electrochemical series)

/ample 2 agnesium plate and copper plate

are placed in 1. mol dm% of sodium chloride,

a'l solution

egati#e terminal (Anode)

agnesium metal (agnesium plate

dissol#es to form g2)

+ositi#e terminal ('athode) 'opper

metal (hydrogen ions !ill be selecti#ely

discharge to form hydrogen gas. *t is

because is lo!er position than

g2 and a in the electrochemical

series)

aniell Cell

*t is another eample of a #oltaic cell.

;olutions are connected by a salt

bridge (inert electrolyte) or a porous pot.


22/28

'athode 'u2 2e –@ 'u (2)

#erall 2'u2 $- –@ 2'u 22

2.

Comparison of &lectrolytic Cells and 'oltaic Cells

;imilarities

/lectrons flo! through the eternal

circuit (connecting !ires)

Anode (oidation) loss of electrons

'athode (reduction) gain of electrons

ifferences

&lectrolytic Cell

Main basic

structures

A battery is needed to

supply electrical energy

&ner$y conversion /lectrical energy –@

chemical energy

#ransfer of electrons

at the positive

terminal

Anode (positi#e

terminal) idation –

anions lose electrons at

the anode

#ransfer of electrons

at the ne$ative

terminal

'athode (negati#e

terminal) 4eduction –

cations accept electrons

from the cathode

&lectrochemistry

*t is an arrangement of elements

according to their tendencies to donate

electrons to form cations.

igher position in the series B a metal

that has a higher tendencies to ionise and

form positi#e ions.

/lectrochemistry is constructed by

the potential difference (#oltage

difference) bet!een pairs of metals and

the ability of a metal to displace another

metal from its o!n salt solution.

A) &lectrochemical Series based on the

otential ifference ('olta$e

ifference)


23/28

/tract useful metals (aluminium,

sodium and magnesium) from its ore

using electrolysis.

anufacture of useful chemical

substances (chlorine and sodium

hydroide) using electrolysis. /lectroplating of iron !ith chromium

to protect the iron layer.

;il#er-plating to ma"e fine cutleries.

oltaic cell (batteries)

/ffect of /lectrochemical *ndustries to!ards

the /n#ironment

ea#y metals (chromium and

mercury) – cause !ater pollution.

'hlorine gas is a toic gas – cause

problem (irritates) to human respiratory

system.

ercury cell (batteries) is highly toic.

*mproper disposal of industrial !aste

– cause !ater pollution.

'hapter 7 acid n basses Acids

An acid is a chemical substance

!hich ionises in !ater to

produce hydrogen ions, 5hydroonium

ions, %

. (a?) 2(l) –@ %

(a?)

/ample 'l(g) 2(l) –@ %

(a?) 'l -(a?)

Acid Acid name Ions

'l ydrochloric acid , 'l -

% itric acid , %-

2;$ ;ulphuric acid , ;$

2-

'%' /thanoic acid , '%'

-

Monoprotic acid B acid can produce

only one hydrogen ion per molecule in !ater. (/ample 'l)

iprotic acid B acid can produce t!o

hydrogen ions per molecule in !ater.

(/ample 2;$)

#riprotic acid B acid can

produce three hydrogen ions per molecule

in !ater. (/ample %+$)

Sodium hydroxide

Bases 5 Al3alis

A base is a chemical substance

!hich reacts !ith an acid to produce

a salt and !ater only.

:ase(s) acid(a?) –@ salt !ater (l).

/ample a(s) 'l(a?) –@

a'l(a?) 2(l)

:ase =ormula ;olubility in !

'opper(**) oide 'u *nsoluble bas

&ead(**) oide +b *nsoluble bas

agnesium oide g *nsoluble bas

Iinc hydroide In()2 *nsoluble bas

Aluminium hydroide Al()% *nsoluble bas

;odium oide a2 ;oluble base

'alcium oide 'a ;oluble base

;odium hydroide a ;oluble base +otassium hydroide 8 ;oluble base

:arium hydroide :a()2 ;oluble base


24/28

etching and dissolution of metals

(purification and etraction of gold)

Sulphuric acid ardous al"ali to neutralise

acidic !aste!ater.

SM Chemistry Form ! 0otes " Acids

and Bases (art 1)

Chemical roperties

important efinition for Acids

onoprotic acid (monobasic acid) is an acid

!hich produce one mole of ion !hen one

mole of the acid ionise in !ater.

Monoprotic

acid

Monoprotic acid

name

'l ydrochloric acid

% itric acid

'%' /thanoic acid

.

olyprotic acids

iprotic acid (dibasic acid) is an acid !hich

produce t!o moles of ios from one mole of

the acid in !ater.

iprotic acid iprotic acid name

2;$ ;ulphuric acid

2'% 'arbonic acid

2'r$ 'hromic acid

2'2$ /thanedioic acid 5

alate acid


25/28

SM Chemistry Form ! 0otes " Acids

and Bases (art ?)

(The above image is 4ust a representation,

colours may vary, so please follow the

colours described in the table below)

#he p7 scale and the Measurement of

p7 'alue of a Solution

p scale is a set of numbers used torepresent the degree of acidity or

al"alinity of a solution.

p is a measurement of the

concentration of hydrogen ions () in the

solution.

p #alue greater than 7 al"aline

solution

p #alue of eactly 7 neutral solution

p #alue less than 7 acidic solution

*n an acidic solution B higher in the

concentration of the ions, the lo!er thep #alue.

*n an al"aline solution B lo!er in the

concentration of the ions, the higher

the p #alue.

p solution can be measured by using

uni#ersal indicator, p paper and p

meter.

p7 value Colour of niversal

Indicator, 1, 2 4ed

% range red

$ range

range yello!

6 Rello!

7 Lreen

0 Lreenish-blue

9 :lue

1 :lue

11 :luish-purple

12, 1%, 1$ +urple

Stron$ Acids

;trength of an acid –

the degree of ionisation or dissociation of

the acid in !ater.

;trong acid – an acid !hich ionises 5

dissociates completely in !ater to

form high concentration of hydrogen

ions ().

/ample of strong acid ineral acid –

hydrochloric acid ('l), nitric acid(%) and sulphuric acid (2;$).

/ample of the strong acid reaction in

!ater 'l(a?) –@ (a?) 'l-(a?) (


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Stron$ Al3alis

;trength of an al"ali –

the degree of ionisation or dissociation of

the al"ali in !ater.

;trong al"ali – an al"ali

!hich ionises 5 dissociatescompletely in !ater to form high

concentration of hydroide ions ( – ).

/ample of strong al"ali ;odium

hydroide (a) solution, potassium

hydroide (8) solution and barium

hydroide (:a()2) solution.

/ample of the strong al"ali reaction

in !ater a(a?) –@ a(a?) -(a?)

Eea3 Al3alis

3ea" al"ali – an al"ali !hich ionises 5

dissociates partially in !ater to form lo!concentrationof hydroide ions ( – ).

/ample of !ea" al"ali ammonia

(%) solution.

/ample of the !ea" al"ali reaction in

!ater %(g) 2(l) VW-@ $(a?)

- (a?)


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acid of different concentration is added

and (iii) an al"ali is added.

0eutralisation

eutralisation B a reaction bet!een

an acid and a base5al"ali to

produce salt and !ater only. Acid al"ali –@ salt !ater

*onic e?uation of neutralisation

(a?) -(a?) –@ 2(l)

Application of 0eutralisation Reactions

in aily Life

igesti#e Tuices in

stomach

:rea" up food (only in acidic condition) and

maintained at p of bet!een

*nsect stings :ees and ants inTect an acidic li?uid into the

s"in but !asps inTect an al"aline li?uid.

base #itration


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Chemistry : Notes Form 4

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Transcript of Chemistry : Notes Form 4