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 formati on 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 sub stan ce w hich ioni ses in………………. t o p rodu ce ………….ion s. The hydrogen ion combines with a water molecule, H 2to !orm a ……………………….. ion, H"# . 2 Acid can be clas si!ie d as a $ s%…………………….acid or a $w %………………….ac id bas ed on its basicity. " &as icity is the number o! ionisab le $h %…………………. atoms per molecule o! an a cid. ' ( ) *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 rea cts with an acid to !o rm a $s%…………... and $w%……………. only. &ases include metal hydroides and metal oides. - i/ e the names o! acids , their !ormu lae and its basicity : 0ame o! acid Formula o! acid &asicity $i% Hydrochlo ric acid $ii% H2' $iii% H0" $i/% thanoic acid 3 4o mplete the i oni5ation o ! a cids below : a% b% c% d% HCl$a6%7 . . .…….$a6%# 4l 8 $a6%……… $a6%7 H # $a6%# 0" 8 $a6% H2SO$a6% 7 ……. …… # ……….. CH!COOH$a6% …………. # 4H"48 $a6%
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
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
<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%
". <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%……………
' <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 :
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%…………….
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"