Chaptet
acidicconditions,sodium hvdrogencarbonate
forms rvater and cart;on dioxide,as sho*'n. (lt
acts as a Lewis base.)
N a H C O r , . o ,1 H * i , q ) - + N a t i " q )+ F I , O , n+ C O : i g )
ln basiccontlitions,sodium hydrogen carbonate
a proton, which neutralizesOH-. In
releases
other words, it acts as an acid. (In both of these
cases,sodium is acruallya spectatorion.)
NaHCO,,. , + OI-I-,"0,-+ Na*1,q)+ HrO,, +
COr2-,"o.,"""'
Although it can act as an acid in basic conditions,
baking soda is considered a weak base.A solution of baking soda has a pH higher than 7. For
more information, do an Internet searchusing
the terms "amphiprotic" and "amphoteric."
(m) Water has a higher meldng point, higher boiling
point, higher speciFcheat capaciry and stronger
surfacetension than nrost similar substances.
The solid form of water (ice) is lessdensethrn
the liquid form.
(n) I{ydrogen bonds are interrnolecularattractions
berweenhydrogen atoms and oxvgen or other
atoms on different rnolecules'
electronegirtive
Due to hydrogen bonds, water has a high boiling point, nrelting point, specificheat capaciw,
and surfacetension.
2 Namesr Formulas'
and Prcpetties
loniccompounds
. nameelemenl
e x a m p l eosi
tarlhesl10lhe iefl ot
rules
namrng
a n dl o r m u l a s periodiclable lrrst
. u s e p r e i i x e lso
Indicatn
e u m b e ro l
aloms
. c h a n g ee n d i n go t
secondelemenlto
"-ide"
(e.9 , dinitrogen
dioxide,NzOa)
. omitthe prellx
"mono-"for the first
elemenl
( e . 9 . ,c a r o o n
dioxide,COz)
' MllR
TF 2-€1
compounds
Molecular
. namemetalfirst
r er^lci
endinn"-i.lo"lo
non-metal
o
eln nnl r rqo nrof ivoc
( e 9 . ,c a r c r u m
c h l o r r dC
e ,a C l z )
. il the metalis a
melal,
transition
identifyion using
stocksystem
( e . 9 . ,i r o n ( l l lo) x i d e ,
FezOs)
o identifypolyatomic
i o n sb y n a m e( e 9 . ,
ammoniumnitrate,
NHaNOs)
AcidsandBases
Tasle Electrlcal Beactiorl
with lltnus
conductiYity
pH
lessthan 7 sour conoucl
acidic
solutions
Reaction
withnetals
wrlh
acroslurn
some
orue
IEdLt
l i t m u s r e d metalsto
produce
Hz(sl
baslc
solulons
greater
than 7
brtter conoucl bases
electricily lurn reo
lrtmus
olue
do noi
lend to
reactwith
YourOwnSummarY
Prcpare
. Srudentscould use tables similar to the examplesthat
follow to summarize all of the key points in Prepare
Your Own Summary.
80-81
BookPages
Student
Gompounds
andMolecular
lonicCompounds
lonlccompoonds
appearance
a
ooour
solidsal
crystalline
room temPerature
may be intensely
coloured
no odour
compounds
Molecular
ma\/
h6
nacoq
solids,or liquidsal
roomlemperalure
usuallywhiteor
coloufless.
. may navea slrong
odour
mellingpornt
. high meltingpoints
. relalivelylow melting
point
abilityto
dissolvein
water
o fiidny easily dissolve
in water
. someare solublern
water
electrical
conductivitY
. conduct electncity
as liquidsand when
dissolvedin waler
. non-conductlve
as
liquids
. may conoucl
electricitywhen
dissolvedin water
KeyTerms
Seeglossaryin srudenttextbook.
l(eyConcepts
Understanding
l. The first step in naming a compound is to determine whether the comPound is ionic or molecular'
2. The element that is farthestto the left on the periodic table is written first. For example,carbon is to
the left of oxygen on the periodic table' Therefore,
in a compound with carbon and orygen (e'g', carbon dioxide), carbon is written first.
(a)
ionic (containsa polyatomic anion)
3.
(b) molecular (contains two non-metals)
(c) ionic (contains a metal and a non-metal)
(d) molecular (hasbeen found to behaveas a molecular substance-is a gas at room temperarure)
4. The compound contains both ionic bonds and
covalent bonds, The sodium ions and nitrate ions
are held together by ionic bonds' The atoms in the
nitrate ion, ho*e'ttet, are held together by covalent
bonds.
lR
2-62
tlHB
. Unif
I Energy and llatter
in Chemical
Ghange
5. Polyatomic ions are made up of more than one
atom, held together by covalent bonds. Collectively,
the atoms have an overall charge. Simple ions contain only one electrically charged atom.
6. (a) one
(b) one
(c) three
7. When an ionic compound is writte4 or named, the
cation ion is placed before the anion.
8. Ionic compounds tend to have most or all of the
following physical properties: high melting point,
soluble in wateq hard, brittle, insulating as solids
and conducting as liquids or in solution. Molecular
compounds tend to have some or all of the following physical properties: low melting point, nonconducting as a solid or liquid, and varying solubility in water but often completely insoluble.
9. Molecular substancesare composed of neutral particles called molecules.Atoms in molecules are held
together by covalent bonds in which atoms share
electrons.As a solid or liquid, molecular substances
have no way to carry charge, and thus do not conduct electricity. In aqueoussolutions, some soluble
molecular substancesbreak apart to some extent
into ions. These substancesmay conduct electricity
to varying degrees.Ionic compounds are composed
of ions held together by ionic bonds. fu a solid, the
ions are tighdy held in a crystal lattice and thus
cannot conduct electricity. As a liquid or in aqueous
solution, however, the ions are free to move and can
conduct electricity.
10. In solid ionic compounds, the ions are tighdy held
in a crystal lattice and cannot move to conduct electricity. In solid molecular compounds, the
molecules are electrically neutral, and do not conduct electricity.
I l. When a molecular substance melts, the covalent
bonds do not break, Instead, the relatively weak
forces that hold one molecule to another break.
12. Wear safety equipment including safety glassesand
gloves.Ifan acid or base is accidentally spilled on
skin, wash with plenty of water. Have sodium
hydrogencarbonate handy for cleaning up spills.
Wash hands thoroughly after working with acids
and bases.
13. The pH of an acidic solution is lower than the pH
of a neutral solution. Acids have a pH lower than 7.
Baseshave a pH greater than 7. The quantity of
hydrogen ions in a litre of an acid is higher than the
quantity of hydrogen ions in a litre of a base.
14. According to Arrhenius, acids ionize to form hydrogen ions, while basesionize to form hydroxide ions.
15. Ice is less dense than liquid water. When a lake
freezes,ice forms at the top, providing insulation
for the water below and ensuring that the lake does
not freeze. This allows fresh-water organisms to
suryive at the bottom ofthe lake.
16. Oxygen atoms have a much stronger attraction for
electrons in a covalent bond than hydrogen atoms
do. Therefore, the elecrons in the bond between
oxygen and hydrogen will spend more time near the
oxygen atom. fu a result, the oxygen atom has a
slight negative charge and the hydrogen has a slight
positive charge.
Skills
Ileueloping
17. (a) magnesiumiodide
(b) aluminium carbonate
(c) calcium oxide
(d) ammonium sulfide
(e) hydrochloric acid
(f) sulfur dibromide
(a)
AlrO,
18.
(b) Ba(oH),
(c) NarP
(d) Na,POo
(e) NH,
(0 si2F4
19. (a) HI1"oy
.o) Hclo(-q)
(c) HNOr,"o,
(d) H3PO4("q)
ProblemSolving/Applying
20. (a) BaF,
O) KBr
(c) NarN
(d) Mg,P,
(e) CaS
21. (a) one
O) rto
(c) four
22. (a) ionic; coloured,crystalline,no odour,high melting point
(b) molecularlgas,odour, non-conductiveas liquid
(c) acid; reactswith magnesium,turns blue litmus
red
(d) molecular;liquid, odour,low boiling point
(e) base;reactswith acid to form a salt and watet
(fl molecular;doesnot conductasa liquid
23. (a) solution A, base;solution B, base;solution C,
acid; solution D, neutral; solution E, acid; solution F. base.
(b) solution F is most basic;solution E is most acidic
ThinkingGritically
24. Sugar(sucrose)and pineapplejuice (fructose)make
the saucesweet,while the acid in vinegar(acetic
acid)and pineapplejuice makethe saucesour.
Chaptcr 2 Nanes,
neutral;the formula
25,(a) LiCt is not electrically
a^
'
-
shouldbe LiCl.
O) KS is not electricallyneutral;the formula should
be K2S.
(c) The formula is correct.
(d) (NHJjSO* is not electricallyneutral; the formula should be (|.{H)rSOo.
Fause&
ffimg*Eg!. Give students an opportunity to return to their original answers to the Focussing questions. Ffave them
modify, amplift, or replace their original answers
based on what they now know.
. Acids corrode (react with) metals. Therefore,
although they would clean up grime and grease,they
might also damage the interior of the oven
l
r
Forrnulae, and Propcr$c3
' tlllt
TB &63