THE MOLE (pp.159 -1.64)

Moles to Particles and Particles to Moles

1. Requires a return to dimensional analysis.

2.· Use this as a conversion factor:

***** Determine the number of atoms in 2.50 mol Zn.

~ 1" _ .d.SOIMJI b .• ~~;~3~***** Determine the number of molecules in 11.5 molHit).

1/. S"".; I (,.0 :lY.I 0 d ~,..fuuL. I .. If1'/~.··..

~tf·

/. S; 'X /0 J~

. ***** Zinc is used as a corrosion-resistant coating oniron and steel. It is also an essential trace element inyour diet. Calculate the number of moles that contain 4;50 x 1024 atoms of Zn .

. ~3 -I--.ft,OaXIO .~

s:

***** Determine the number of moles that contain 3.75 x 1024 molecules of CO2.

,;1.'/ J i/3. 75 X 10 /l11~

***** Determine the number of molecules in 3.25 mol of AgN03.- ,

.1. d S "'~ I" .OJ. ~ (0d -:rt.J... I / m.•..f

***** Determine the number of moles that contain 2.50 x 1020 atoms Fe.OIl) -I- I..:? So 'f.. f 0 o.,Al."rrt.a I ~ Fe

1),1t~ Fe z , hi . e~3 .t, oJ. x/a Jcn1-::1 F;

OVER

=~1

I, 96 'I (()<wlV~

Mass and the Mole

1. The mass in grams of one mole of any pure substance is called its Mo LA-!. W14SS

***** Chromium is a transition element used as a coating on metals and in steel alloys to control corrosion;calculate the mass in grams 0[0.0450 mol. Cr.

3 c .***** Determine the mass in grams of each of the following:,

a. 3.57 mol AI .

d&.18 A-/11~'.fA-e

b. 42.6 mol Si

c. 3.45 mol Co'

.1. ({S M'~ ('1) S' il, Cj.3JCoI - Im,.p CD

z

: 1/ 9t. olof .:-

***** Calcium, the fifth most abundant element on earth, is always found combined with other elementsbecause of its high reactivity. Calculate the number of moles ofCa in 525g Ca.

=

a. 25.5g Ag

***** Determine the number of moles in each of the following:. - - --

b. 125g Zn

II. q/ m~ -Zr}

c. l.OOg Fe

1.003 Fe

Mass to Atoms and Atoms to Mass

1. By using molar mass and Avogadro's number one cart convert mass to number of atoms (particles) andnumber of atoms (particles) to mass.

******* Gold is one of a group of metals known as the coinage metals (copper, silver, and gold).Determine, the number of atoms of gold in a pure gold nugget having a mass of25.0g.

~-3tt.Od..Y.fO ~~

.tJd

7,~(I 'X 10 ~t.<>

***** Determine the number of atoms in each of the following samples:

a. 55.2g Li

b. 0.230g Pb,

c. 0.120g Ti .

If~JTt 021: I.SI X/O~,

***** A party balloon contains 5.50 x 1022 atoms of helium gas. Determine the mass of the gas.

***** Determine the mass in grams of each of the following:

a. 1.00 x 1024 atoms Mn~cf +

J Mt) s: /' 00 'f (0 ~I

5 t.f • tj"l.J /111

/InA n,

b. 1.50 X 1015 atoms N

,S J I/!Vtre ,J J'I.o Is IJ -F-1,5·0 y: (0 d-etl11-a z: :3 ,Y q '" I 0 ~jN ~.g~ , 1'V\. •.1. tJ.- /t.OJ. 'l.fO .

c. 1.50 X 1015 atoms U

/' So 1- (O,,s"~ U I",; U ;) 38, o 3J U -7jU :. s.q3 y: 10J= .23 IhL~ UI it . 0 ~ y ro .cd()f114

Molar Volume- .

1. Since the mole is the most convenient unit for counting numbers of atoms or molecules, theM.oL.A~ ","OLV M t ofa gas is defined as the volume that one mole occupies at O.OOoC

and 1.00 atm pressure.

2. These conditions are known as standard temperature and pre~sure: SrP3. At STP, ImJ ;;}d.. L{ L

***** Determine the volume that 0.881 mol of gas at STP will occupy:

}Q,7 L

***** Determine the number of moles of carbon monoxide inside a container having a volume of22.8 L.

***** Determine the volume, in liters, occupied by 2.65g of krypton.

L ;:

***** Determine the following:

a. The mass of xenon gas present in a 2.50L balloon "ItSTP.

::

b. The volume, in liters, of H occupied by 0.0459 mol of H,

L =C'J..-,_O_l(_3_q_IVl_.-O~(--_1 --.1 ~ .~ . q L ~r I ~V\-.-t H

:./.03 L

THE MOLE TRAFFIC CIRCLE:

111\0 LAQ. ~3.~-'- rvV-\SS- <t! G--C it .O;;J.'{../O"" I\s,s 1-

. ",oLES ..< ..X /' P.4ena/,;J

~) ~'7 v "",bLAI( i> . 013- - &.OdJ. 'f.. 10 '1'IV'AS-S' .

-:r :::rS . ni'-' ~ '1J\J '\'

IfMOLAR MASS OF A COMPOUND (pp, 165 - 170) \

1. Molar mass: the sum of the molar masses of all the atoms represented by one mole of formula units.

2. To calculate the molar mass of an ionic compound, you must add the individual molar masses of all theatoms in the compound. " .

***** Calculate the molar mass of Kl,

K'" (i) ~ll. (0 z: s«. (():r z: (I) 'L~-1() -;. 12.~_qt)

III It ~00 J/,-rto--e

***** Calculate the molar mass ofFe203.

~.e.. ~ (~) 5$ - fS t: 111·7-0

0-' (~)(~ -00 :- t( F. 00

,511.70 3J~v-f

OVER

***** Calculate the molar mass of Ah(S04)3

Af : (s ) ~~. 9 f s: S 3- 9"

S:: (:~) .3J.. 0" x: C;c . {g()::: (IJ) 1&.00 = Iq~· 00

3 tf d ·(y ~«~

a. CZH50B

***** Calculate the molar mass of the following compounds:

C .: (~)(-l!- ((p)

() = (I)

;2lf-O a.

~. 0 "

I~, 0'0

<I c.os J/~t.J.·

Id·Ol .:

'.0,

~ '" (I) .39. to r:

C::- CJ.) I~·O/':-

1+-- (.3) 1.0/:

0:: CJ.) (ft,of) :.

39. (0

J,l{.O J.

3.03

.J.)..O 0

C .: (L» I d· 0 I:: 7J. .0 b

f.i:: (10) '.01: 10,/0

S:: (!~)-.3;)~ofo;. .J~--Q~~~

If If. a ().!JIM)

MASS RELATIONSHIPS or PERCENT COMPOSITION (pp. 171 - 174)

1. One way to determine the amount of an element in a compound is to calculate its percent composition.

2. To determine the percent composition, remember that the molar mass is 100% of the mass representedby theformula. ~

- --~----- ----- ~ - ---.. -~ -- --- - - ---- -- ,- --- -- ~------ --

3. The percentage of each element in the compound is simply the molar mass of the element divided by themolar mass of the whole compound and multiplied by lOO~

4. The equation looks like this:

TOTALI'Vl0 LNZ M 1.\<;S' 0 F T1-I-G" lEL!:'Jv\ c::tJ T

(100 )

***** Determine the percent composition ofMgCh

nu= (() d-,,~-1.n s: ;;'1.3 Q

'CJ c: ( '))3 S. t( S z 70 • q ()o s. cLO 7v Cl= 10. $'v

--- (10'0) z: 7',1. i{ 7 'Zes. J..() '"

***** Determine the percent composition ofNH4N030)&.0), 3 S:,QOZ,;.j ; (2-)/lj.Ol z .;If·o~ %AJ .r (we>I .:so .».«

H = ell) 1-.vI ' z: l/,OL{

45.0'0 7cJ 1-1 - a.o if {too) s: s. OS 10(~ ) Ilc,O() , - - -~o.o:0 -z:

so .o ~C{P.O{)%0 s: (r OTi ) s9- 96 %;-£1).06

***** Determine the percent composition of each of the following:, Cfs.1f

a. Na2S04 Z Al'l'- J' , (wo)~~ .: (';1) 02~.qq -' l{-S.qP IV'()

$= (I) BJ.Olo= JJ.O~

o ;: (t() 1(P.cJU ;: GV,d ()It{ .J.·O ~

b. H3P04

If .s: (3) /.0 I ': 3.03

P ~ (t) .30,Ql:; JO. Cf7

() :: (4) /&.00:; ~V·o-o9£· OD

7u S 3J.o"((00) .s: d:J· $7%::

IY,) .0((

%0 (. C/.06 ({(Io) .r tjS. ob Z '.: --1<{,j·OL{

3.0370 H :: ~ (100)"::

P ~o,Cj 2 _10 z 9'f. oo (roo)-

, v, 06) VI7'f.dJ (!()~ : ~ S. 3/ t»OVER

7,,-Aio.;I,;).9fj

(too) 37%- ..: OJ 7.: &'l{.O I

c. NaHC03

Nt\ z Ct ).;2:J. qq .;J,). q c; loH z1.0,_

(wo) /, ;2.0%gt(.01s

4 - (( ) It01 :0- I . (7 (-

C '" (I) Ll.Q I z Id.O 1 10 C: IJ"O/ (too ) ::: Ill. ,J () % .IiP.do L/f. O"()

?Ct, 0 I

o :: ( Q) .:

ff'l. o J 700 z:<f rf. 0 {J_

(((J{)) -- .s 7. I Lj ~.gl« 01

WATER IN A HYDRATE

1. Some salts can bind water molecules within their crystal lattice structures.

2. When this happens, these compounds are known as H 'f DRA-IE-S

3. Because they can absorb water, many salts are used as drying agents.

4. Chemical formulas for hydrates look like this:

***** Determine the percent calciuni chloride, CaCh • 6H20, is CaCh

C~:: (I) ~0 . 0 ¥ s: <{ 0 . 0 S- % r1Cia:: 110. 9JCl =- (d.) ~5 . L(S:- 7a Ji 0 c:n 9, (0

/( o. q? z $0. ~.s%H"LO.: (~) (~.o2. = IDf.-I~

CJlq,IO

(IO() )

***** Determine the percent iron (III) chloride, FeCb • 6H20, is Fecb

Fe. .: (I) ss. ~5 s: ss. &> S

(3) J S .l\ S .:: 10 (Po 3 S-!W d. s.o

ho o")

-c)70. dd

DETERMINING FORMULAS FROM PERCENT COMPOSITION DATA(pp. 174 - 185)

EmpiriCal Formula. .

1. When a new chemical substance is discovered, its discoverers often do not know its formula or its .composition.

2. The new compound is put through a series of reactions to determine theelemerits in it and the mass ofeach element present. The chemical formula of the compound can then be calculated.'

3. The key is to convert the percent composition data to' MO L. E..5

.4. Then compare the mole amounts to find the simplest whole number ratio. The ratio tells you how manyatoms of each element are in the chemical formula:

* * * * * Determine the chemical formula of a compound formed by mercury arid chlorine given thefollowing data:' .. .

%Hg=73.90% z: I

%CI = 26.10% '; 01-(, • I 0 --37.3 -1'0.u». ~0

***** Potassium dichlorate, an orange solid, contains the three elements potassium, chromium and oxygen.Analysis of the sample gives the following data: . .

%K=26.60% %0=38.00% %Cr = 35.40%

z: • ,,~,

1< - /-IC

(1, . ~fJ ':-J-k. - . ~ f-o

d~.I.rO

31'./Q

3;,38"00 0 J. = 3.S-d, :3g. ~ . sso0 ,---- .; I~ -

~ IG·oj)

(1< C.- 03" ) )(~ - k'~c. 07-

OVER

***** Determine the empirical formula of a compound containing carbon, hydrogen and nitrogen given thefollowing data:

%C == 38.67%

C ~ .3 ~. ~ 7_~ i:

/2..10

%H == 16.23%

~Z ~ r

%N = 45.10%

u .o 7

qs. to .

14.013. ~.~::

Molecular Formuias

1. Empirical formulas provide information as to what is in the compound by indicating the simplest wholenumber ratio of atoms. '. !

2. But, they do not always tell exactly how many atoms of each element are presentin a molecule of thecompound. For that one needs the MoLEtL!l4t. R.1OOvUC! .'

3. Molecular. formula -aformula that gives the type and actual number of atoms in a chemical compound.. ,

4. The molecular formula can provide' one with a better idea of the molecule's properties based on exactlyhow many of each atom there will be, in a molecule,

. .. . .

5. In some cases the empirical formula is the same as themolecular formula (H20).. . . .

6. In most findings this is not the case:

Empirical Formula Molecular Formula Name

t1-l1-0 cJl2-0 Fof(tI\.\tL\Ll>84'f D(5

en. 0 C~I~'10;J ttct:nC AC;J)

Ct~.J-() C & U,;t Of, C lUClJS13

Ds.te-r-m-in.i.n-g-Mo.!8Gu-la-!!--Fo.r-m ulas-;

1. In the previous example, the molecular formulas were simply a multiple of the empirical formula.

2. A similar relationship exists between the molar masses of the empirical formula and that of thecompound.

***** Determine the molecular formula ofa compound having an empirical formula ofCH and a molarmass of 78.11 glmol. ?!..:J.L

'X ~ I ~ •0 d-- = s. 1q c: (,C~ (I) 1~.QI:

1~:Cdl.~l=

I.:J.O J1.0 I

/3 , OJ.

•

76.54% C . 12.13% H 11.33% 0

r z: (If) 12-. 0 1:- I ~8 . (J t'J

1-+ :- ell) I. rJ \:;- 11. n

o z: cd lit· OQ:- '" < 00.. -

***** A compound has the following composition:

If its molar mass is 282.45 glmol, what is its molecular formula?

7~ s: e. :: ~ =9(1.. o , (., I ~ 7 0 ,70 ~

141. 2(,

t+ .~ I d.,0 0 B .: ~ '::17= z:0 170S'\,.0 1

\ I. 3~ .70f 0 s: /-0 s: - :. 0-111.00

Cctl-f 11 0

STOICmOMETRY

Stoichiometry and Balanced Equations

1. A balanced chemical equation uses chemical formulas to show the identities and relative amounts of thesubstances involved in a chemical reaction.

2. The reaction of powdered iron filings and oxygen is:

One can say four atoms of iron react with three molecules of oxygen to produce two molecules of iron (III)oxide.

One can also say four moles of iron react with three moles of oxygen to produce two moles of iron (III)oxide.

3. But one e.1!l·t-J"-lO" read this reaction in terms of mass amounts.

4. Ifwe convert from moles to mass, we can then obtain information regarding the masses of the reactantsand products involved:

j r-e. _- L/ "",J. F~ J. S:,f5 S I--e.I 1 t Yn-.J. Fe..

~1O~.:- ~""-,J. Oa+ 3:1·00 ,5 () ~

I In,..,.L0 J-.

J •..•..~ f.='e.t- () 3. \ -1~9, 1,J ~'l-(13I I .:» Fel.03

The total mass of the reactants and total mass of the products are equal.

OVER

Mole Ratios

1. The coefficients in chemical equations indicate the relationships among moles of reactants and products.

2. The relationship between these coefficients can be used to write conversion factors calledl'vt.OLEQA-TlO J

3. Arnole ratio is aratio between the number of moles of any two substances in a balanced chemicalequation .

.***** Determine all the mole ratios that can exist in the following chemical equation:

2AI (s)+ 3Br2 (1) -+ 2AlBr3 (s):

J .~ut A ~ .J""'~J4~3h'-~ (Jr-~ :11v\) ,4l.Br-3

3wi.J. 8i{d,.,.~4·Q

3~n~~,Sr'L.;}m~ .4~$fj

~hU!4-e'&-3;l.--u.c.. ,4Q

~.~.M tJrj3•....1 .erb\

4. Mole ratios are the key to calculations based upon a chemical equation.

STOICmOMETRIC CALCULATIONS·

Mole - to - Mole Conversions

I. One can determine the moles of a reactant needed ormoles of a product formed if one knows thebalanced chemical equation and the number of moles of either one reactant or one product.

***** Determine the number of moles of hydrogen gas produced when 0.0400 moles of potassium are usedin the following reaction:

2K (s) + 2H20 (1) -+ 2KOH (aq) + H2 (g)

o ,0 {/()0 h1J. /( \ 1.V\..e [~d...--- .- --, ....- -r .;r~~;(-Ic.

***** Sulfuric acid can be produced as follows:

2S02 (g) + 2H20 (1) + O2 (g) -+ 2H2S04 (aq)

If 12.5 moles of S02 are used, determine the moles of H2S04 produced.

I:). S .;» SO'J... n-jl SOh1.,.{' '1; 1../

-_ ..- --- ._------ -.- - ---. ----_._--_ .._- .._---_._-----_ ...._---------------_._-_. --_.- ------.- ..---- -- ._--

If 12.5 moles of S02 are used, determine the moles of O2 needed.

***** Methane and sulfur react to produce carbon disulfide and hydrogen sulfide:

2C~ (g) + S8 (s) -> 2CS2 (I) + 4H2S (g)

Determine the moles of CS2 produced when 1.50 moles of S8 are used.

I.ro J:vlS; all~JCSa.1 IWtJ S~

Determine the moles of HiS produced when] .50 moles of Sg'are used.

/. SO ,.~ Sg 'I. 4.~J~-4SI J'ld! S~"

Mole - to- Mass Conversion

1. Add one step to the railroadtracks to convert moles of desired material to mass .

. * * * * * Determine the mass (g) of sodium chloride produced when 1.25 moles of Cls reacts with N a: metal.

2Na (s) + Ch (g) -> 2NaCI (s)

1,;5 fin) tfJ

***** Determine the mass (g) of chlorine gas needed to react 1.25 moles of titanium (IV) oxide in thefollowing reaction:

TiOi (s) + C (s) + 2Ch (g) -> TiCl4 (s) + CO2 (g)

/77. J5

OVER

* * * * * Calcium hydride reacts with water according to the following reaction:

CaH2 (s) + 2H20 (1) --+ Ca(OHh (aq) + 2H2 (g)

Determine the mass (g) of Ca(OH)2produced when 2.50 moles of CaH2 react.

;: I 8S t 01 'S -Determine the mass (g) of H20 required to react with 2.50 moles of CaH2..

;90, /8-

Mass - to - Mass Conversions

1. This is more typical of what a chemistneeds to know.

2. These require conversions of mass to moles, then the use of the mole ratio and then ~conversion ofmoles to mass;

***** Ammonium nitrate decomposes when heated:

NH4NOJ (s) --+ N20 (g)+ 2H20 (g)

Determine the mass (g) of H20 produced when 25.0g ofNfuNOJ decomposes .

.,1S'.c, D ~I"uO 3J' .

s: \ \ ,d.-S

***** Methyl salicylate, CsHsOJ, also known as oil of wintergreen, is most often made in it synthesis-reaction between methaaol.and.salicylic. acid,-G'lH&Q.g .-Detem1i..t:],e-the-mass--~g~-of-sa!icyEc-acid.required.to.produce 325g of methyl salicylate.

,; J. I tcj C~14~03

o 2_ OlCfS- d I. ~. 0;.,)-- g-.

LIMITING REACTANTS

Why Do Reactions Stop?

1. Reactions stop when one of the reactants is used up. The reactant that is used up first is called thel\ M \T1.J6 . t<.rnCIAAJ T . It limits the extent of the reaction and, thereby, determines the amount of~~ .

2. A portion of all of the either reactants remains after the reaction stops. These leftover reactants arecalled FX tcS oS . R.J?A-cn:\,JTJ .'

3. Previous calculations were based on having the reactants present in the amounts needed.

4. To determine the amount of product formed when one reactant is limiting, one must first determinewhich reactant is the limiting reactant. .

Calculating the Product Wbena Reactant is Limited

***** Disulfur dichloride is used to vulcanize rubber, a process that makes rubber harder, stronger, andless likely to become soft when hot or brittle when cold. It is produced by reacting sulfur and chlorine asfollows:· . ..

S8(1) + 4Ch (g) -+ 4S2Ci2 (1)

Determine the mass (g) ofS2Ch produced when 200.0g of S8 and IOO.OgofCh react.

S·C)" <2()O·O ·S~ Irn~SG. tf~l~.5&.C-P~J. J ~~=dS~. q ~ S8' I f>tvf .s;

j/h(c-f Ci~70~7oJC1J

YtwJ ~ Cia111-/ d--P CJ~

13$.0')5 S';}'Cf;)i:» s, C}:L

OVER

***** Determine the mass (g) oftetraphosphorus decoxide, P401O,produced when 25.0g of phosphorus, P4,reacts with 50.0g of oxygen, O2•

P4(S) + 502 (g) -> P40JO (s)

j Plj 0,0 :: ~S '05 P'f I~J! Plf

I I~ s. "s ~LI_

IWtJ ~ OroIY"tv-f Pct

c1 ~3L B-fJ Pet ato

/ I'VL~~ ~ DIu - S7,3 ..~'j

J~O,O :- So. 0 O~ 'Wt~Oa ,~~ (0,0 .{,1.tS'3, te PoC{ 10 ST, 7,·'],1.,09.; 0 if p<{ Otd

:

SWI J.(j s, I .:»

. .

*****Silver nitrate and sodium phosphate react to produce silver phosphate and sodium nitrate:

3AgN03 (aq) + Na3P04 (aq)-> Ag3P04 (s) + 3NaN03 (aq) •If200.0g Na3P04 and 200.0g AgN03 are used in this reaction, determine:

a. the mass of solid silver phosphate produced

·A PC} 0200,0 /\ Al03 / I>t~ 4J tJO-3J 'j31. « z .. ... /(09. JWJ 1!"vOJ

IW1J Ay 3 fa"3~~ lyll.i03

4/ G-,st..J A 31()'1

11>1 vi) ';~J Po q

e f~I.«3j

0200.0 A1({J /rJ'1I

s: SIO, {;, f- ~"O-

b. the limiting reactant

L)j;JO 3

c. the reactant in excess

tJa.3 PO ((

h, .3, 9Y.t Ak J ltJy/;1'/~' AiQ3 A '1

PERCENT YIELD

1. Most chemical reactions do not succeed in producing the predicted amount of product.

2. The TH8J~IlCA L ,( I~ is the maximum amount of product that can be produced from agiven amount of reactant.

3. TheAC:r\)A L'II \'::L:b . is the amount of product actually produced when the chemicalreaction is carried out in an experiment

4. The ratio of the actual yield to the theoretical yield expressed as a percent is thePazCCU"T' 'f \El.J) . ofa product. It is a measure of the r~action' s efficiency.

GJ ACTUAL Yt i::-"l...U "\

/o'l18i) ;::'T}J~O~-nCAt'ft aD (100') .. , '. -. 5. The actual yield comes from actual experimentation while the theoretical yield comes from

stoichiometric calculations:

***** When potassium chromate, K2Cr04, is added to a solution containing O.500g silver nitrate, AgN03,solid silver chromate, Ag2Cr04, is formed ..

Determine the theoretical yield of silver chromate.

1m,) 4 iJ03• :soD

If 0.455g of silver chromate is actually produced, calculate the percent yield.

***** Zinc reacts with iodine in a synthesis reaction. Determine the theoretical yield ofzinc iodide if125.0g ofzinc are used. Determine the percent yield if 515.6g ofzinc iodide are actually produced.

Zn (s) + h (s) -> Znh (s)

j 7" T., __ _IO!_S~P~'Q_l:~r\/,1W\-;J~7 A~I~IM=~~l,~....-=' T~",-~-=-7~{/~ac.:.72c., .J.. 0. ..J - I • I • , 'T' ~ ( L, ( ''J C1\ IJ,

I CoS& j ~ ~f) IM~ :tv) ) ~~ th -L~ / fO 1---(0 r cxJ

515, (,

{PIO, d.

OVER

---- ------ -------- -- ----- -- ---- --------------------- ----- - - ----- ----