modul chem faida 2.docx

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CHAPTER 7 – ACIDS AND BASES

A ACIDS AND BASES

Learning Outcomes

You should be able to:

• State the meaning of acid, base and alkali

• State uses of acids, bases and alkalis in daily life

• Explain the role of water of water in the formation of hydrogen ions to show the properties of

acids

• Explain the role of water in the formation of hydroxide ions to show the properties of alkalis

• Describe chemical properties of acids and alkalis

Activity 1 Meaning of acid ,base and alkali

Fill in the blanks with the correct words:

1 An acid is a chemical substance which ionises in………………. to produce ………….ions.

The hydrogen ion combines with a water molecule, H2 to !orm a ……………………….. ion,

H"#.

2 Acid can be classi!ied as a $s%…………………….acid or a $w%………………….acid based on its

basicity." &asicity is the number o! ionisable $h%…………………. atoms per molecule o! an acid.'

(

)

*onoprotic acid : ne acid molecule $i%………………to $o%………..hydrogen ion

+iprotic acid : ne acid molecules $i%………………to $t%…………..hydrogen ion

A base is a substance that reacts with an acid to !orm a $s%…………... and $w%…………….

only. &ases include metal hydroides and metal oides.- i/e the names o! acids, their !ormulae and its basicity:

0ame o! acid Formula o! acid &asicity$i% Hydrochloric acid$ii% H2'

$iii% H0"

$i/% thanoic acid

3 4omplete the ioni5ation o! acids below :

a%

b%

c%

d%

HCl $a6% 7 . . .…….$a6% # 4l8 $a6%

……… $a6% 7 H# $a6% # 0" 8 $a6%

H2SO $a6% 7 ……. …… # ………..

CH!COOH $a6% …………. # 4H"48 $a6%



Activity 2 "

Fill in the blanks with correct words:

1

2

"

A base is a substance that reacts with an acid to !orm $s% ......................and

$w% ............................ only.

amples o! bases are metal oides and metal hydroides that contain oides ion , 28 and

hydroide ion, H8 such as 4opper$99% oide and *agnesium hydroide

An alkali is a water8soluble base which ionises in water to produce………..………..........,H8 .

ome eamples o! bases which dissol/es in water are sodium oide, ammonia and

potassium hydroide' 4omplete the table below

0ame o! alkali Formula o! alkali$i% odium hydroide$ii% H$iii% Ammonia a6ueous

( 4omplete the ioni5ation o! !ollowing alkalis :

0aH $a6% 7 …….$a6% # H8 $a6%

……… $a6% # H2 $l% 0H'# $a6% # …………. $a6%

' ;ses o! acids, bases and alkalis

$a% To use as …………………. … reagent

ample: sodium hydroide solution, sulphuric acid, hydrochloric acid$b% To ..................................................................................................... ……………

ample: thanoic acid $/inegar%, ben5oic acid

$c%To make /arious ………………..

ample: *agnesium oide antacid medicine, Ascorbic acid /itamin 4$d%To produce …………., detergent and ………………

ample: sodium hydroide to make soap and detergent

*agnesium hydroide added to tooth8paste$e%To manu!acture dyes,……………………. and drugs

ample: methylamine$!%;sed in rocket !uel

ample:…………………………………………………………………………………………(Refer to page ! " #$ %hemistry textbook&



Activity !" #ole of $ate% and its &%o&e%ties of acids and alkalis

Fill in the blanks with correct words.

1 An acid only shows its …………..…… properties when dissol/e in ……………………….

2 9n the presence o! water, the acid ionises to !orm ……………………………………..ions ." <ithout water, an acid still eists as…………………and there are no ................ ions present.

' lacial thanoic acid, 4H"4H is an eample o! acidic substance.

4omplete the !ollowing table to show the role o! water in acidic properties.

4ondition o! ethanoic acid !!ect on the blue litmuspaper

9n!erence

lacial ethanoic acid, +oes not show acidicproperties

thanoic acid in water

thanoic acid in dry propanone$ organic sol/ent %

( An alkali only shows its ……………….. properties when dissol/e in ………………………..) 9n the presence o! water, the base dissociates to produce …………………………... ions that

are responsible !or the ………………… properties- Ammonia,0H" is an eample o! alkali.

4omplete the table below to show the role o! water in alkaline properties.

4ondition o! ammonia !!ect on the red litmus paper 9n!erence+ry

A6ueous $dissol/ed inwater%

how alkalineproperties

+issol/ed in propanone,$organic sol/ent%

Activity " C'e(ical &%o&e%ties of acids

Acids are $s%……….. in taste. Acids solution ha/e pH /alue less than -. Acids change the colour

o! indicators as shown in the table

9ndicator 4olour o! indicator in acid solution&lue litmus paper

;ni/ersal indicator range and red

=henolphthalene 4olourless

*ethyl orange >ed



2 Acids react with bases to !orm salts and water only. &ases are metal oides or metal hydroide.

<rite the chemical e6uation !or the reaction between sulphuric acid and copper$99% oide.

……………………………………………………………………………………………………..." Acids react with reacti/e metals to produce salts and hydrogen gas.

<rite the chemical e6uation !or the reaction between hydrochloric acid and 5inc .

……………………………………………………………………………………………………...' Acids react with metal carbonates to produce salts, water and carbon dioide gas.

<rite the chemical e6uation !or the reaction between nitric acid and calcium carbonate.

……………………………………………………………………………………………………...



Activity ) " C'e(ical &%o&e%ties of alkalis1 Alkalis are $b%……………. in taste and !eel $s%…………… Alkalis solution ha/e =h /alue

more than -. Alkali change the colour o! indicators as shown in the table

Indicato% Colo*% of indicato% in acid sol*tion>ed litmus paper

;ni/ersal indicator &lue and purple=henolphthalene

*ethyl orange yellow

2 Alkalis react with acids to !orm salts and water only

<rite the chemical e6uation !or the reaction between sodium hydroide and ben5oic acid.

……………………………………………………………………………………………………...2 <hen a miture o! an alkali and an ammonium salt is heated, ammonia gas is liberated.

<rite the chemical e6uation !or the reaction between sodium hydroide and ammonium

chloride .

……………………………………………………………………………………………………..." Alkalis react with most metal ion solutions $ cations % to produce the insoluble metal

hydroides or precipitate 8 $precipitation reaction%



<rite the chemical e6uation !or the reaction between sodium hydroide and iron$99% sulphate.

……………………………………………………………………………………………………...B" +'e st%engt' of acids and alkalis

ea%ning O*tco(es" You should be able to:

• State the use of a p' scale• Relate p' alue with acidic or alkaline properties of a substance

• Relate concentration of hydrogen ions with p' alue

• Relate concentration of hydroxide ions with p' alue

• Relate strong or weak acid with degree of dissociation

• %onceptualise )ualitatiely strong and weak acids

• %onceptualise )ualitatiely strong and weak alkalis

Activity -" +'e &H scale

Fill in the blanks with correct words

1 The pH scale $ ? to 1' % , is used to indicate the degree o! $a%……………… or $a%…………….o! a solution.

2 pH /alue less than - , indicates an…………………………solutionpH /alue e6ual to - , indicates a…………………………solutionpH /alue more than - , indicates an…………………………solution

"

Acids 0eutral

Alkalis

? 1 2 " ' ( ) - 3 @ 1? 11 12 1" 1'

Acidity ......................................$increase or decrease %

Alkalinity.........................$increase or decrease %

Activity . " St%ong and $eak acid1. 4omplete the !lowchart below to understand the concept o! strong acid and weak acid2. trong acid is an acid that ioni5es $c%………………….. in water to produce $h%

…………….. concentration o! $h%………………….. ion



". <eak acid is an acid that ioni5es $p%………………… in water to produce $l%……………concentration o! $h%…………………. ion

Strong acid Weak acid

Degree of dissociation

Ionization in water

Concentration of ions

pH value

Examples

Activity /" St%ong and $eak alkali

1. 4omplete the !lowchart below to understand the concept o! strong alkali and weak alkali.2. trong alkali is an alkali that ioni5es $c%…………………… in water to produce $h%……………

concentration o! $h% ………………. ion". <eak alkali is an alkali that ioni5es $c%…………………… in water to produce $l%……………

concentration o! $h% ………………. ion'.

Strong alkali Weak alkali

Degree of dissociation

Ionization in water

Concentration of ions



pH value

Examples

C" CONCEN+#A+IONS O0 ACIDS AND AAIS

ea%ning O*tco(es You should be able to:

• State the meaning of concentration

• State the meaning of molarity

• State the relationship between the number of moles with molarity and olume of a solution

• Describe the methods for preparing standard solutions

• Describe the preparation of a solution with a specified concentration using dilution method

• Relate p' alues with the molarity of acids and alkalis

• Sole numerical inoling molarity of acids and alkalis

Activity 1 " Concent%ation of acids and alkalis

Fill in the blanks with the correct answers.

1

2

The concentration o! a solution re!ers to the 6uantity o! solute in 1dm" o! solution

4oncentration can be de!ined in two ways :8

$a% 4oncentration in g d(3!

$b% 4oncentration in (ol d(3!

$4oncentration in (ol d(3! is also known as (ola%ity or molar concentration $* % %

2 The two units o! concentration can be inter8con/erted:

Work tis out *

" (.? g o! copper$99% sulphate is dissol/ed in water to !orm (?? cm" solution. 4alculate theconcentration o! copper$99% sulphate solution in g dm8" B

C *olar mass

4oncentration in............................4oncentration in ...................

D *olar mass



E +nswer: * g dm"-

' <hat is the mass o! sodium carbonate re6uired to dissol/e in water to prepare 2?? cm"

solution that contains (? g dm8" B

E +nswer: g

( '.? g o! sodium carbonate powder, 0a24" , is dissol/ed in water and made up to 2(? cm".<hat is the molarity o! the sodium carbonate solutionBE>elati/e atomic mass: 4, 12G , 1)G 0a, 2"

. +nswer: */ mol dm"- 0

Activity 11The number o! moles o! solute, n in a gi/en /olume o! solution and the molarity o! * can becalculated by using the !ormula :

n 0umber o! moles o! solute* *olarity o! solution $mol dm8"% olume o! solution $dm"%

9! the /olume is in cm" I con/ert the /olume o! solution !rom cm" to dm"

( 4alculate the number o! moles o! ammonia in 1(? cm" o! 2 mol dm8" a6ueous ammonia.

E +nswer: *- mol ) A student pipetted 2?.? cm" o! potassium hydroide , H solution into a conical !lask. The

concentration o! the alkali was 1.( mol dm 8" . 4alculate the number o! moles o! potassium ,H in the !lask.

n ! "#

n = MV

1000

n = M x V

1000o%



E +nswer: *- mol dm"-

- 4alculate the number o! moles o! hydrogen ions present in 2?? cm" o! ?.( mol dm8" sulphuricacid, H2'.

E +nswer: *1 mol of ' 2 ions

Activity 12 " 4%e&a%ation of Standa%d sol*tions

1 <hat is a standard solutionB

……………………………………………………………………………………………………

2 =reparation o! standard solutions by 5eig'ing (et'od $mass o! solute% :8

Ste& 1 : 4alculate the mass o! solute needed .

mass n C molar mass

* C molar mass 1???

ample: To prepare 1?? cm" o! 2.? mol dm8" sodium hydroide solution. 4alculate the mass o! 0aH needed. E>elati/e atomic mass: 0a, 2" G , 1) G H, 1

mass n C molar mass

* C molar mass 1???

2.? C 1?? C '? 3 g1???

$r% tis:$a% To prepare 2(? cm" o! 1.? mol dm8" sodium carbonate solution. 4alculate the mass o! 0a24" needed. E>elati/e atomic mass: 0a, 2" G , 1) G 4, 12

.+nswer : 13*/g0

$b% ?.2( mol dm8" solution o! sodium hydroide was prepared by dissol/ing x g o! sodiumhydroide in -(? cm" o! water. <hat is the /alue o! x B

E>elati/e atomic mass: 0a, 2" G , 1) G H, 1

n = mass

molar mass

n = MV

1000



.+nswer : 4*/ g0

Ste& 2 "*atch the descriptions J procedures with the correct diagram below.

• <ash and rinse the weighing bottleor small beaker and !ilter !unnel toensure no solute remains in anyo! the apparatus used.

• Trans!er the dissol/ed solute into a

suitable /olumetric !lask.

$a%

• Add water slowly by using a

dropper to bring the le/el o! thesolution to the calibration mark.

• The /olumetric !lask is closed

tightly and in/erted se/eral times toget a uni!orm or homogenoussolution.

$b%

• 4alculate the mass o! solute

needed.

• <eigh out the eact mass o! solute

needed in a weighing bottle.

• +issol/ed the solute in a small

amount o! distilled water.

$c%

• Add more water care!ully to the

/olumetric !lask and swirl gently.• hake well to ensure thorough

miing.

$d%

Activity 1! " 4%e&a%ation of Standa%d sol*tions by Dil*tion (et'od

1 +ilution method

Ste& 1 : 4alculate the /olume o! stock solution re6uired by using the e6uation:8

*1 molarity o! solution be!ore dilution 1 /olume o! solution be!ore dilution *2 molarity o! solution a!ter dilution 2 /olume o! solution a!ter dilution

ample: (? cm" o! ?.1 mol dm8" sodium hydroide, 0aH solution !rom 2.? mol dm8"

M161 7 M262

<hen using the e6uation M161 7 M262 ,

make sure that both 1 and 2 are o!the same unit.



sodium hydroide,0aH solution

&e!ore dilution A!ter dilution

*1 1 *2 2

2.? mol dm8" B ?.1 mol dm8" (? cm"

2.? 1 ?.1 (? 1 ?.1 (? 2.( cm"

2.?

$r% tis: 1?? cm" o! ?.( mol dm8" potassium manganate$99% ,*n' solution is prepared!rom 1.? mol dm8" potassium manganate$99% ,*n' solution. 4alculate the /olume o! thesolution

E +nswer : / cm-

Ste& 2*atch the diagram with the correct descriptions below.

$a%

$b%

$c%

$d%

• Add water slowly by using a dropper to

bring the le/el o! the solution to thecalibration mark.

• The /olumetric !lask is closed tightly and

in/erted se/eral times to get a uni!orm or homogenous solution.

• Trans!er the stock solution to a suitable

/olumetric !lask.

• 4alculate the /olume o! stock solution

re6uired.

• ;se a pipette to draw up the re6uired

/olume o! stock solution.

Activity 1 " +'e &H val*es and (ola%ity of acids and alkalisFill in the blanks with correct words . ;se words gi/en in the bo.



5ncreases decreases concentration hydrogendissociation higher hydroxide alkali

1 The pH /alue o! an acid or an alkali depends on three !actors :

$a% degree o!…………………………………………………………………………………….

$b% molarity or ………………………………………………………………………………..

$c% ………………….. o! the acid or …………………………………………………………..2 The lower the pH /alue, the ……………….. the concentration o! ……………………ions.

" The higher the pH /alue, the …………….. the concentration o! …………………... ions.

' As the molarity o! an acid increases , the pH /alue o! the acid ………………………….

The pH /alue o! an alkali increases when the molarity o! the alkali ………………..…….

D " NE8+#AISA+ION

ea%ning O*tco(es

You should be able:"

• Explain the meaning of neutralisation*

• 6rite e)uations for neutralisation

• Explain the applications of neutrali7ation in daily life

• Describe the titration process of acid"base

• Determine the end"point of titration during neutrali7ation

• Sole numerical problems inoling neutralisation

Activity 1) " Ne*t%alisation

1 <hat is the meaning o! neutralisationB

………………………………………………………………………………………………..

2 <hat are the only products o! neutralisationB

………………………………………………………………………………………………….

3 <rite a balanced chemical e6uation !or the neutralisation o! the !ollowing reactions:8

$a% nitric acid and barium hydroide

……………………………………………………………………………………………

$b% sulphuric acid and sodium hydroide

……………………………………………………………………………………………

$c% ethanoic acid and potassium hydroide



……………………………………………………………………………………………

44omplete the !low chart below:8



Activity 19 " Acid : base +it%ation

1 <hat is a titrationB

9s a method used to determine the $/%…………… o! acid needed to neutrali5e completely o! aknown /olume and concentration o! alkali with the help o! indicator

2 <hat is the !unction o! an indicatorB

To show $e%……………. point o! titration" 4omplete the table below.

9ndicator 4olour in solution

Acid 0eutral Alkali

Red litmus paper 8lue litmus paper

9henolphthalein

ethyl orange

4 <rite out the procedure !or carrying out an acid8base titration to determine the vol*(e o!nitric acid ?.( mol dm8"

needed to neutralise 2( cm" potassium hydroide ?.( mol dm8" .Kabel the diagram.

olume o! alkali is measured accurately using $p%…………….

Transfer the alkali into (c)……………… (f)………………. Add

2 to 3 drops of indicator

Fill burette with acid. Record initial readin



Acid solution fro! (b)…………..is added slowl" into the conical

flask. #wirl the contents of the flask

$ontinue addin acid until the indicator chanes colour. Record

final burette readin

Activity 1- " N*(e%ical &%oble(s involving ne*t%alisation

;se!ul e6uations in sol/ing numerical problems in/ol/ing neutralisation.:

n no o! moles* *olarity o! solution olume o! solution in dm"

*a molarity o! acid

*b molarity o! alkalia /olume o! acidb /olume o! alkali

a and b mole ratio o! acid to alkali in a balanced chemical e6uation

ample:9n an eperiment, 2( cm" o! sodium hydroide solution, 0aH o! unknown concentrationre6uired 2).(? cm" o! 1.? mol dm8" sulphuric acid, H2' !or complete reaction in titration.4alculate the molarity o! sodium hydroide.

6rite out a balanced chemical e)uation:

H2SO ; 2NaOH Na2SO ; 2H2O a 7 1 (ol b 7 2 (ol

*aa 1*bb 2

,1.? C 2).(? 1*b C 2(.?? 2

*b 2 C 1.? C 2).(? 2.12 mol dm8"(olarity of sodium hydroxide&

n = mass

molar mass

n = MVMaVa = a

MbVb



2(.??

1 <hat is the /olume o! 1.( mol dm8" a6ueous ammmonia re6uired to completely neutralise"?.?? cm" o! ?.( mol dm8" sulphuric acid B

2NH! ; H2SO <NH = 2SO

E +nswer: 1 cm-

2 4alculate the /olume in cm" 2.? mol dm8" hydrochloric acid that is re6uired to reactcompletely with 2.)( g o! sodium carbonate.E>elati/e atomic mass: 0a, 2" G , 1) G 4, 12

E +nswer: 1/ cm-

" 2( cm" o! sulphuric acid was neutralised with 13.? cm" o! sodium hydroide 1.? moldm8". 4alculate

$a% the number o! moles o! sulphuric acid that is used in this reaction.$b% the molarity o! sulphuric acid

.+nswer (a& *; mol (b& *-3 mol dm"- 0

' 2' cm" o! ?.1 mol dm8" 0aH is re6uired to completely neutralise 2?.? cm " o! sulphuric acid.4alculate the concentration o! sulphuric acid in$a% mol dm8"

$b% g dm8"



.+nswer (a& *3 mol dm"- (b& /*!! g dm"- 0

( <hat is the molarity o! phosphoric acid i! 1( cm" o! the acid is neutrali5ed by "3.( cm" o! ?.1(mol dm8" 0aH B

.+nswer (a& *1! mol dm"- 0

modul chem faida 2.docx

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