EXAMINATION QUESTIONS FOR AMOUNT OF SUBSTANCE
1.
Nitroglycerine, C3H5 N3O9, is an explosive which, on detonation, decomposes rapidly to form a large number of gaseous molecules !he e"uation for this decomposition is given below #C3H5 N3O9$l% & '(CO($g% ) '*H(O$g% ) +N ($g% ) O($g% $a%
samp sample le of nitro nitrogly glycer cerine ine was was detona detonated ted and and produ produced ced *35 *35* * g of oxygen oxygen gas gas $i% $i%
-tat -tatee wha whatt is is mea meant nt by the the ter term m one mole of molecules
$ii%
Calculate Calculate the numbe numberr of moles of oxyge oxygen n gas produced produced in this this reaction reaction,, and hence hence deduce the total number of moles of gas formed Moles of oxygen gas Total moles of gas
$iii%
Calculate Calculate the the number number of of moles, moles, and and the mass, of nitrogly nitroglycerine cerine detonated detonated Moles of nitroglycerine Mass of nitroglycerine (7)
(b) (b) A seco second nd samp sample le of nitr nitrog ogly lyce ceri rine ne was was plac placed ed in a str stron ong g seal sealed ed cont contai aine nerr and and – detonated. The volume of this container was 1.00 × 10 m . The resulting decomposition produced a total of 0.!" mol of gaseous products at a temperature of 1100 1100 #. -tate the ideal gas e"uation and use it to calculate the pressure in the container after detonation 2'
2'
$!he gas constant R constant R . /3' 0 1 mol % Ideal gas equation Pressure (4) (Total 11 marks)
2.
-odium chlorate$%, NaClO3, contains ('+4 by mass of sodium, 3334 by mass of chlorine and #5'4 by mass of oxygen $a%
se the the above above data data to show that that the the empirical empirical formula formula of sodium chlorate$% chlorate$% is NaClO3
$b%
-odium -odium chlo chlorat rate$ e$%% may be prep prepare ared d by passin passing g chlori chlorine ne into into hot hot a"ueou a"ueouss sodium hydroxide 6alance the e"uation for this reaction below 77 Cl( ) 77 NaOH & 77 NaCl ) NaClO3 ) 3H(O () (Total marks)
$otassium nitrate% #&' % decomposes on strong heating% forming oygen and solid Y as the only products. 3.
$a %
'** g samp ample of of 1NO 3 $ M M r . '*''% was heated strongly until fully decomposed into ! $i% $i%
Calc Calcul ulat atee the the num number ber of of mol moles es of 1NO 1NO 3 in the '** g sample
$ii% $ii%
t (9/ (9/ 1 and '** '** 8a, 8a, the oxygen oxygen gas gas produc produced ed in this this decomp decomposi ositio tion n occupi occupied ed a 2#
3
volume of '(( : '* m -tate the ideal gas e"uation and use it to calculate the number of moles of oxygen produced in this decomposition 2'
2'
$!he gas constant R constant R . /3' 0 1 mol % Ideal gas equation Moles of oxygen (")
$b%
Compound ! contains #594 of potassium and '+54 of nitrogen by mass, the remainder being oxygen $i% $i%
-tat -tatee wha whatt is is mea meant nt by the the ter term m empirical formula formula
$ii%
se the the data data above above to to calcul calculate ate the the empir empirica icall formula formula of of ! (4)
$c% $c%
;edu ;educe ce an an e"ua e"uatio tion n for for the the deco decomp mpos osit itio ion n of 1NO 1NO 3 into ! and oxygen (1) (Total 1# marks)
.
The e*uation for the reaction between magnesium hydroide and hydrochloric acid is shown below
23
Calculate the volume, in cm , of '** mol dm hydrochloric acid re"uired to react completely with '** g of magnesium hydroxide (4) (Total 4 marks)
=hen aluminium is added to an a"ueous solution of copper$>>% chloride, CuCl (, copper metal and aluminium chloride, lCl3, are formed =rite an e"uation to represent this reaction
".
(1) (Total 1 mark)
$.
$a%
?ead$>>% ?ead$>>% nitrate nitrate may be produc produced ed by the reactio reaction n between between nitric acid and lead$>>% lead$>>% oxide as shown by the e"uation below bO ) (HNO 3 → b$NO3%( ) H(O 3
23
n excess of lead$>>% oxide was allowed to react with '@5 c m of '5* mol dm nitric acid Calculate the maximum mass of lead$>>% nitrate which could be obtained from this reaction (4)
(b) (b)
An e*ua e*uatio tion n repr repres esen entin ting g the the ther therma mall deco decomp mpos osit itio ion n of lead lead(+ (++) +) nitr nitrat atee is show shown n belo below w. (b$NO3%($s% & (bO$s% ) #NO ($g% ) O ($g% sample of lead$>>% nitrate was heated until the decomposition was complete t a temperature of 5** 1 and a pressure of '** 8a, the total volume of the gaseous mixture 2#
3
produced was found to be '5* : '* m $i%
-tate -tate the the ideal ideal gas gas e"uatio e"uation n and and use it to calcul calculate ate the the tota totall number number of of moles moles of of gas produced in this decomposition 2'
2'
$!he gas constant R constant R . /3' 0 1 mol % Ideal gas equation
.............................................................. ......................................................................................... ...........................
Total Total number of moles of gas $ii% $ii%
;edu ;educe ce the the num numbe berr of moles moles,, and and the the mass, mass, of NO NO ( present in this gaseous mixture $>f you have been unable to calculate the total number of moles of gas in part $b%$i%, 23
you should assume this to be ((3 : '*
mol !his is not the correct answer%
Number of moles of NO( Mass of NO( (7) (Total 11 marks)
7.
$a %
mmonia, NH3, reacts with sodium to form sodium amide, NaNH (, and hydrogen =rite an e"uation for the reaction between ammonia and sodium 7 7 (1)
(b) A salt% X% contains 1,.- by mass of magnesium% 1!./ by mass of nitrogen and ,./ by mass of oygen. $i% $i%
-tat -tatee wha whatt is is mea meant nt by the the ter term m empirical formula formula 7 7 7 7
$ii% $ii%
;ete ;eterm rmin inee the the empi empiri rica call for formu mula la of X 7 7 7 7 7 7 7 7 () (Total 4 marks)
(a) (a) the e*uation below. 8.
Amm Ammoniu onium m sulp ulphate hate rea reacts cts with with a*ueo ueous sodi sodium um hydr hydro oide ide as show shown n by
$NH#%(-O# ) (NaOH
→
(NH3 ) Na(-O# ) (H(O 3
23
sample of ammonium sulphate was heated with '** cm of *5** mol dm a"ueous sodium hydroxide !o ensure that all the ammonium sulphate reacted, an excess of sodium hydroxide was used Heating was continued until all of the ammonia had been driven off as a gas 3
!he unreacted sodium hydroxide remaining in the solution re"uired (@3 cm of 23
*+** mol dm hydrochloric acid for neutralisation $i%
3
23
Calcul Calculate ate the origin original al numb number er of of mole moless of NaOH NaOH in '** cm of *5** mol dm a"ueous sodium hydroxide 7 7 7 7
$ii% $ii%
3
23
Calc Calcul ulat atee the the numb number er of of mole moless of HCl HCl in in (@3 (@3 cm cm of *+** mol dm hydrochloric acid
7 7 7 7 $iii%
;educe ;educe the number number of moles of the the unreacted unreacted NaOH neutra neutralised lised by the hydrochloric acid 7 7
$iv%
se your your answers answers from from parts parts $a% $i% $i% and $a% $iii% $iii% to calculate calculate the the number number of moles of of NaOH which reacted with the ammonium sulphate 7 7 7 7
$v%
se your your answe answerr in part part $a% $a% $iv% $iv% to calcu calculate late the num number ber of of moles moles and the mass mass of ammonium sulphate in the sample $>f you have been unable to obtain an answer to part $a% $iv%, you may assume that the number of moles of NaOH which reacted with ammonium sulphate e"uals 2(
(@/ : '* mol !his is not the correct answer% Moles of ammonium sulphate 7 7 Mass of ammonium sulphate 7 7 7 (7)
–
(b) (b) A 0.1 0.1g g gas gaseous eous samp ample of ammo mmonia nia occ occupie upied d a volu olume of -.!, .!, × 10 m at a temperature T and a pressure of 100 $a. -tate the ideal gas e"uation, calculate the number of moles of ammonia present and deduce the value of the temperature T 2'
2'
$!he gas constant R constant R . /3' 0 1 mol % Ideal gas equation Moles of ammonia 777 777 7 7 Value Value of T 777 777 7 7 777 777 7 7 777 777 7 7 777 777 7 7 (4) (Total 11 marks)
%.
Compound A is an oxide of sulphur t #'5 1, a gaseous s ample of A, of mass *3*# g, 3
occupied a volume of '(@ cm at a pressure of '*3 8a -tate the ideal gas e"uation and use it to calculate the number of moles of A in the sample, and hence calculate the relative molecular mass of A 2'
2'
$!he gas constant R constant R . /3' 0 1 mol % Ideal gas equation alculation (Total " marks)
A hydrocarbon% W, contains /-. carbon by mass. mass. The relative molecular molecular
10.
mass of W is "!.0 $a% $a%
Calc Calcul ulat atee the the empi empiri rica call form formul ulaa of & ........ ........ ........ ........ ........ ........ ........ ........
$b% $b%
Calc Calcul ulat atee the the molec molecul ular ar form formul ulaa of & ........ ........ ........ ........ (4) (Total 4 marks)
11.
$a% $a%
One One isot isotop opee of sodi sodium um has has a rela relativ tivee mass mass of (3 (3 Calculate the mass, in grams, of a single atom of this isotope of sodium 2'
$!he vogadro constant, ! constant, !,, is +*(3 : '*(3 mol % (2) (Total 2 marks)
12.
$a%
-tate what is meant by the term empirical formula.
$b%
chromium chromium compou compound nd contains contains (/#4 of sodium sodium and and 3('4 3('4 of of chromium chromium by mass, the remainder being oxygen ox ygen Calculate the empirical formula of this compound (4) (Total 4 marks)
(a) (a)
13.
Tita itanium ium(+) (+) chlo chlori rid de reac reacte ted d with with wate waterr as as sho shown in the the foll follow owin ing g
e*uation. !iCl#$l% ) (H (O$l% → #HCl$a"% ) !iO ($s% 3
!he reaction produced (** cm of a '(*< solution of hydrochloric acid Calculate the number of moles of HCl in the solution and use your answer to find the original mass of !iCl# Moles of "l. "l. .......................................................... ........................................................................................ .............................................................. ............................................. ............. Mass of Til #......................................................... ....................................................................................... ..................................................... ....................... (4)
$b%
Calculate Calculate the volume volume of ''* < sodium sodium hydroxid hydroxidee solution solution which would be re"uir re"uired ed to to 3
neutralise a '** cm portion of the '(* < solution of hydrochloric hydrochloric acid ()
$c% $c%
3
n excess excess of magnes magnesium ium metal metal was was adde added d to a '** '** cm portion of the '(* < solution of of hydrochloric acid Calculate the volume of h ydrogen gas produced at 9/ 8a and (*AC
14.
$a%
Calcul Calculate ate the the maxim maximum um mass mass of sodiu sodium m sulph sulphide ide that that can can be obta obtaine ined d from from '** '** g of sulphur
(2)
$b%
3
Calcul Calculate ate the minimu minimum m volum volumee of hydrog hydrogen, en, in cm cm , at (9/ 1 and '*'3 8a, that is needed to form 5** g of hydrogen sulphide
() (Total " marks)
1".
=hen a sample of li"uid, X' of mass *#*+ g was vaporised, the vapour was found to occupy a 2#
3
volume of (3# : '* m at a pressure of ''* 8a and a temperature of #@3 1 $a% $a%
Bive Bive the the nam namee of the the e"ua e"uati tion on pV pV . nRT. . nRT. (1)
$b%
se th the e" e"uation pV $ pV $ nRT to calculate the number of moles of X in the sample and hence deduce the relative molecular mass of X. 2'
2'
$!he gas constant R constant R . . /3' 0 1 mol % Moles of X Relati%e molecular mass of X (4)
(c ) 2ompound X, which contains carbon% hydrogen and oygen only% has !." carbon and /.,! hydrogen hydrogen by mass. 2alculate the empirical empirical formula of X. ()
$d%
sing sing your your answers answers to to parts parts $b% and and $c% $c% above, above, dedu deduce ce the the molecu molecular lar form formula ula of X (1) (Total % makrs)
1$.
$a% $a%
23
Calcu Calcula late te the the conc concen entr trat atio ion, n, in mol mol dm dm , of the solution formed when '9+ g of hydrogen 3
chloride, HCl, are dissolved in water and the volume made up to (5* cm ()
(b) The carbonate of metal M has the formula 3 -2'. The e*uation for the reaction of this carbonate with hydrochloric acid is given below. <(CO3 ) (HCl
→
(
sample of < (CO3, of mass *39# g, re"uired the addition of ('@ cm of a 23
*(+3 mol dm solution of hydrochloric h ydrochloric acid for complete reaction $i%
Calcul Calculate ate the number number of mole moless of hydroc hydrochlo hloric ric acid acid used used
$ii% $ii%
Calc Calcul ulat atee the the numb number er of of mol moles es of of < (CO3 in *39# g
$iii% Calcul Calculate ate the the relative relative molec molecula ularr mass mass of < (CO3 $iv% $iv%
;edu ;educe ce the the rel relat ativ ivee atom atomic ic mass mass of of M and hence suggest its identity Relati%e atomic mass of M Identity of M ($) (Total % marks)
17.
$a %
!he ma mass of on one mo mole of 'H atoms is '**@/ g and that of one 'H atom is 2(#
'+@3# : '* g se these data to t o calculate a value for the vogadro vogadro constant accurate to five significant figures -how your wor8ing (2)
$b%
How does does the the numb number er of atom atomss in one one mole mole of argo argon n compar comparee with the num number ber of of molecules in one mole of ammonia (1)
(c ) A sample of am ammonia gas occupied a volume of of 0. 0.04- m at -/! # and /!.0 $a. 2alculate the number of moles of ammonia in the sample. –1 –1 (The gas constant R 5 !.1 6 # mol ) ()
$d%
3
solutio solution n conta containi ining ng *@3 *@3( ( mol mol of amm ammoni oniaa was made made up to to (5* (5* cm in a volumetric flas8 by adding water Calculate the concentration of ammonia in this final solution and state the appropriate units (2)
$e%
diff differe erent nt soluti solution on of ammoni ammoniaa was reacte reacted d with sulph sulphuri uricc acid as shown shown in the the e"uatio e"uation n below (NH3$a"% ) H(-O#$a"% 3
→
$NH#%(-O#$a"%
23
>n a titration, (5* cm of a '(# mol dm solution of sulphuric acid re"uired 3*/ cm 3 of this ammonia solution for complete reaction $i% $i%
Calc Calcul ulat atee the con conce cent ntra rati tion on of amm ammon onia ia in thi thiss solut solutio ion n
$ii% $ii%
Calcul Calculate ate the the mass mass of ammon ammonium ium sulp sulphat hatee in the the soluti solution on at the the end end of this this titration ($)
(f ) The reaction of magnesium nitride% 3g &-% with water produces ammonia and magnesium hydroide. 7rite 7rite an e*uation for this reaction. (2) (Total 1$ marks)
1.
$a %
;efine th the te term relati%e molecular mass mass (2)
$b% $b%
Bive Bive the the mea meani ning ng of the the ter term m empirical formula formula (1)
$c %
Compound X contains 3(9 % by mass of carbon and '#*4 by mass of hydrogenD the remainder is oxygen $i% $i%
Calc Calcul ulat atee the the empi empiri rica call for form mula ula of of X.
$ii% $ii%
!he !he rel relat ativ ivee mol molec ecul ular ar mass mass of of X is '#+ ;educe its molecular formula formula (4)
(d) (d)
A 1.0 1.0 g sam sample of meth methaane was burne urned d in air. ir. +t rea reacte cted as foll follow owss8 CH# $g% ) (O ( $g% $i% $i%
→ CO( $g%
) (H (O$g%
Calc Calcul ulat atee the the numb number er of of mol moles es in in '* '* 8g 8g of of meth methan ane e
$ii% $ii%
Calcul Calculate ate the the volume volume of of oxygen oxygen gas, gas, measur measured ed at (9/ (9/ 1 and '** '** 8a, 8a, which which would would be re"uired for the complete complete combustion of '* 8g of methane ($) (Total 1 marks)
Bive the meaning of the term mole as mole as used in the phrase Eone mole of moleculesE
1%.
(1) (Total 1 mark)
2#.
$a%
=hat =hat is the the name name given given to the the numb number er of molec molecule uless in one one mole mole of carbo carbon n dioxid dioxide e (1)
(b)
(i)
9tate the ideal gas e*uation.
$ii% $ii%
Calcul Calculate ate the the volum volumee of '** '** mol mol of carb carbon on dioxi dioxide de gas gas at (9/ (9/ 1 and '** 8a 8a 2'
2'
$!he gas constant R constant R . . /3' 0 mol 1 % $iii%
Calculate Calculate the the mass of of carbon carbon dioxide dioxide gas gas at (@3 (@3 1 and and 5** 8a 8a contained contained in a 3
cylinder of volume ***5** m (7)
$c%
Hydrog Hydrogen en can be be made made by the reac reactio tion n of hydro hydrochl chlori oricc acid with with magn magnesiu esium m accord according ing to the e"uation (HCl )
→
=hat mass of hydrogen is formed when '**cm of hydrochloric acid of concentration 5* 23
mol dm reacts with an excess of magnesium ()
(d) (d) A com compoun pound d of of iro iron n con conta tain inss !. !./ / by mass mass of iron iron and and 1,. 1,." " by mass ass of of car carbo bon% n% the the remainder being oygen. $i% $i%
;ete ;eterm rmin inee the the empi empiri rica call form formul ulaa of the the iro iron n comp compou ound nd
$ii% $ii%
=hen =hen one mole mole of this this iron iron compou compound nd is heate heated, d, it decom decompos poses es to give give one mole mole of of iron$>>% oxide, FeO, one mole of carbon dioxide and one mole of another gas >dentify this other gas $!he molecular formula of the iron compound is the same as its empirical formula% (4) (Total 1" marks)
21.
mmonium nitrate can be prepared by the reaction between ammonia and nitric acidG NH3 ) HNO3 → NH# NO3 $a%
23
!he concen concentra tration tion of a nitr nitric ic acid acid solution solution is (** (** mol dm Calculate the volume of this solution which would be re"uired to react with exactly (** g of ammonia (4)
(b) (b)
A sam sample ple of ammo ammoni nium um nitr nitrat atee dec decom ompo pose sed d on on hea heati ting ng as sho shown in the the e*u e*uat atio ion n bel below ow.. NH# NO3 → (H(O ) N( ) O( On cooling the resulting gases to (9/ 1, the volume of nitrogen and oxygen together was 3
found to be **5** m at a pressure of 95* 8a $i%
-tate -tate the the ideal ideal gas gas e"uatio e"uation n and and use it to calcul calculate ate the the tota totall number number of of moles moles of of 2'
2'
nitrogen and oxygen formed $!he gas constant R . R . /3' 0 mol 1 % $ii%
sing your answer to part part $b%$i $b%$i%, %, deduce deduce the numbe numberr of moles of ammonium ammonium nitrate nitrate decomposed and hence calculate the mass of ammonium nitrate in the sample Moles of ammonium nitrate Mass of ammonium nitrate ($) (Total 1# marks)
22.
'(
2(3
!he mass of one atom of C is '99 : '* g se this information to calculate a value for the vogadro vogadro constant -how your wor8ing (2) (Total 2 marks)
The e*uation below represents the thermal decomposition of #2l' .
23.
(1ClO3$s% $a%
→
(1Cl$s% ) 3O ($g%
Calcul Calculate ate the the mass mass of of oxygen oxygen whic which h could could be be produ produced ced by the the comple complete te decomposition of '#@ g of 1ClO 3
(2)
$b% $b%
3
Calc Calcul ulat atee the the mass mass of 1ClO 1ClO3 re"uired to produce '** dm $at (* AC and '*'3 8a% of oxygen
() (Total " marks)
24.
$a%
=hat =hat experim experimenta entall data are are re"ui re"uired red in orde orderr to calcul calculate ate the the empiric empirical al formu formula la of a compound (1)
$b% $b%
Bive Bive the the mea meani ning ng of the the ter term m molecular formula. (1)
(c )
7hen barium nitrate is heated it decomposes as follows8 6a$NO3%($s% → 6aO$s% ) (NO ($g% ) O ($g% $i%
Calcul Calculate ate the total total volu volume, me, measur measured ed at at (9/ (9/ 1 and and '** 8a, 8a, of gas which which is is produced by decomposing 5** g of barium nitrate
$ii%
Calculate Calculate the volum volumee of '(* < hydroch hydrochloric loric acid which is re"uire re"uired d to neutralise neutralise exactly the barium oxide formed by decomposition of 5** g of barium nitrate 6arium oxide reacts with hydrochloric acid as follows 6aO$s% ) (HCl$a"%
→ 6aCl($a"%
) H(O$l%
(7) (Total % marks)
2".
!he mass spectrum of a compound has a molecular ion pea8 at mI & & . . '+/ Jlemental analysis shows it to contain #(94 carbon, (#4 hydrogen h ydrogen and '+@4 nitrogen by mass !he remainder is oxygen Calculate the empirical and molecular formulae of this compound (4) (Total 4 marks)
2ompound X contains only boron and hydrogen. The percentage percentage by mass of boron in X is !1.-. +n the mass spectrum of X the pea at the largest value of m/z occurs at 4. 26.
$a%
se the the perc percenta entage ge by mass mass data data to calc calcula ulate te the the empir empirica icall formu formula la of X
$b% $b%
;edu ;educe ce the the mole molecu cula larr for formu mula la of X (4) (Total 4 marks)
27.
$a %
;efine th the te term relati%e molecular mass mass (2)
$b%
'(
2(3
!he ma mass of on one ato atom m of of C is '993 : '* g se this mass to calculate a value for the vogadro constant $ ! $ !%% showing your wor8ing (1) (Total marks)
2.
=hen iodine reacts directly with fluorine, a compound containing 5@(4 by mass of iodine is formed $a%
;eterm ;etermine ine the empiri empirical cal formu formula la of of this this compo compound und
$b%
!he empir empirica icall formula formula of this this comp compoun ound d is the same same as the the molecu molecular lar form formula ula =rite a balanced e"uation for the formation of this compound (4) (Total 4 marks)
2ompound A (3r 5 -14.!) contains --.- carbon% ."1 hydrogen and ".04 bromine by mass. 9how that the molecular formula of A is 2:!;r-.
29.
() (Total marks)
