Mole Exam Mark Scheme

1.2 PRACTICE EXAMINATION QUESTIONS MARK SCHEME

1.

(a) (a)

(i) (i)

23

Avogad ogadro ro’’s num numbe ber/ r/co cons nsta tant nt of mole molecu cule les/ s/pa part rtic icle les/ s/sp spec ecie iess / 6 × 10 [Not ‘atoms’]

1

Or same number of particles as (there are atoms) [Not molecules]

in 12.(00)g of

(ii)

12



1

0.3$0  &2 !oles "2 # 32 (# 1.0% × 10  mo  mol)

1

 &2

(iii (iii))

# 2% (× 1.0% × 10 ) [Accept answers via 4 separate mole calculations]

1

# 0.316 & 0.31' mol anser to 3* sf+ [Mar [Markk cons conseq eq on on err erro ors in in M1/ M1/M2 M2]]

1

 &2

!oles !oles of nitr nitrog ogl, l,ce cerin rinee # - × 1.0% × 10 [Mark conseq on teir moles o! " 2 ]

(1) (1)

(# 0.0-3 mol)

 M r  of  of nitrogl,cerine # 22' or number string

1 1

!oles of nitrogl,cerine # 22' × 0.0-3 # %.%0 & %.%3(g) [answer to #$ s!] [%! strin& "' ut !inal answer wron& ten allow M ut A* !or  M+] [Mark conseq on error in M r  ]

[,enalise wron& units] units]

[,enalise si&- !i&- errors once onl. in wole question]

(b)

n p # n or p # or p #  0.'3 × .31 × 1100 n 1.00 × 10 −3 p # /  # # '%00%3 or '%0 or '.  '.% [i&nore s-!-]

1 1 1

units # a or a or !a

(as appropriate) 1 [%! error in conversion !rom ,a treat as a contra0iction o! te units mark] [%! trans!er error error mark conseq ut penalise M2] [%! 0ata !rom outsi0e o! aove use0 penalise M2 an0 M#] [%! p epression incorrectl. rearran&e0 penalise M2 an0 M#] [i! 3  1#+# ' use0 penalise M2] [11]

2. (a)

4a

l "

21.6 23

33.3 3$.$ -$.1 16 1

 0.  0.%(3%)

0.%(3) 2.(2)

5ence

1 1  3 1

Accept bacards calculation7 i.e. from formula to 8 composition7 and also accept route via ! r  to 239 3$.$9 -7 and then to 113 [%! 5 values incorrectl. copie0 allow M1 onl.] [%! an. wron& Ar values/atomic numers use0  6*  78 (b)

3l2 * 64a"5 → $4al * 4al" 3 * 352"

1 [3]

3.

(penalt, for sig fig error #1mar per :uestion) (a )

=3

(i)

moles ;4"3 # 1.00/101.1 # %.% < 10  (m  (mol)

1

(ii)

p # n or n # p/

1

 p1 

100000 × 1.22 × 10 & -

moles "2 # n #  93   # (1)

.31 × 2%

2

 (1)

 # -.%3 < 10=3 (mol) 1 (mark answer !irst : ceck ack i! wron&) (transcription error lose M# mark M4 conseq on error) (i! ‘untraceale’ !i&ures !i&ures use0 M#M47) (i! wron& temp conversion : lose M# : conseq M4) (i! n  93/p 6* lose M# an0 M4)

(b) (b)

(i) (i) (ii)

simp simple lest st/l /lo oes estt rat ratio io of atom atomss of of eac each h / elem elemen ent/s t/s in a com compo poun und d/ substance / species / entit, / molecule

1

 '

N

-$.% 3%.1

"

16.$ 3'.6 1-

16

(1) 1.1' 1

1.1 2.3$ 1

2

;4"2 3

(1)

(M# tie0 to M2) (M# can e trans!erre0 !rom equation i! ratio correct  ut *; not &iven) (i! calc inverte0 lose M2 an0 M#) (i! use0 At N 1 /  wron& No !or Ar ten 6* lose M2 an0 M#) (i! 5 o! " missin& awar0 M2 onl.)

(c )

2;4"3 > 2;4"2 * "2 or fractions/multiples

1

(accept 2 'N"# < ' 2 N   N 2"4 $ "2 )  ) (0o N"3 accept ‘=’ in equation) [10]

 4.

(penalt. !or si& !i& error 1mark per question)  M r (!g(4"3)2 # $(.3) (i! $(.3) (i! At N> use0 lose M1 an0 M2)

1

2

moles !g("5)2 # 0.01'2 (conse: on rong ! ) (anser to 3* s.f.)

1

moles 5l # 2 < 0.01'2 # 0.03-- or 0.03-3 (mol) (process mark)

1

0.03-3 × 1000 1

vol 5l # (i! can0i0ate

used  7-71+  7-71+

# 3-.3 & 3-.$ (cm 3) (unless wron& unit)

1

or 7-71+1 lose M2)

(?ust answer wit no workin& i! in ran&e  (4)- i! s a. #4 ten (2)) (i! not 2@1 ratio lose M# an0 M4) (i! work on 6l 6*  7/4) [4]

2A1* 3ul 2

5.

→

2A113 * 3u9 (accept multiples/!ractions) "  2*

2A1* 3u * 3u9

→ 2A1

3*

1 [1]

6.

(a )

moles 5403

# 1'$ ?

 &3

10  < 1.$ # (0.262$ mol)9 moles b(4"3 )2 0.262$ # (0.131 mol)9 !r  b(4"3 )2 mass b(4"3 )2  0.131#-3.$ g9 (accept 4#-2 B 4#-C) (M1 D M2 are process marks- %! error in M1 or in M2 0o not mark M4 consequentiall. i-e- 0o not awar0 M4) (i! atomic numers use0 in M# 0o not awar0 M4)

1 # @< 1 # 331(.2)9 1 #331.2 1

(b)

(i)

p # n9 n=

 p/ 

1  &-

=

100000 ×1.$ ×10 .31 × $00

1

 &3

#

3.61 ? 10  9 (%! pressure not converte0 to ,a ma 2)  93  (%! n 

(ii)

9

p1 

1

 use0  6*E M2  M#  7)

moles402

# -/$ -/$ <

 &3

3.61 < 10 9 [mark is !or use o! 4/F]  &3

 2.% < 10

1  &3

"9 1.'<10 9

1

!r  4"2

# -69 1

mass4"2

#  &3

-6 <2.%
# 0.1.33(g) "9 0.021 (g)9 1 ( i! atomic numers use0 M#  M4  7) [11]

7.

(a )

(b) (b)

24a * 2453

(i) (i)

→ 

24a452 * 52

(or multiples)

Bim Bimples plestt rat ratio io of atom atomss of of eac each h ele elem ment ent in in a comp compou ound nd / sub subst stan ance ce / species / entit, / molecule

(ii)

1

1

!g "

4 1

16.2

16.2 1.%

(2-)

2-.3

1-

6-.% 16 (7-+F)

0.66' 1.3' -.06 1 1 6 !g42"6

2

(Mark M1 !irst- %! an. wron& Ar  use0  6*  7) (Accept M&(N" 3 )2 !or M# i! aove workin& sown) [4]

8.

(a )

 &3

< 0.$00

 &2

100
#

$.00 < 10

(ii)

2'.3 <10 < 0.600

#

1.6- < 10  / 1.63 < l0  (m  (mol) onl,

(iii)

1.6- <10  (m  ( mol)  Mark conseq on (ii)

(iv)

$.00 < 10 = 1.6- < 10 # 3.36 < 10  (m  (mol)  Mark conseq on (i) D (iii)

(v)

3.36 < 10  < G  1.6 < 10  (mol)  Mark conseq on (iv)

 &3

(mol)

 &2

(i)

accept $ <10  / 0.0$

 &2

1

 &2

1

 &2

 &2

1

 &2

 &2

 &2

 &2

1

 &2

 &2

 %! 2-+C H 17  used 1.3% < 10

 &2

1

 &2

1.6 < 10  < l32(.l)

or 1.3% < 10  < 132(.l) 1

 Mark !or M r  # 2.22 g

(b)

or 1.3 g 1

p # n

1

n = 0.1-3 1'

# .-(1) .-(1)  &3

< 10  (m  (mol)

1 100000 × 2.6 ×10−-

 p/

=

n 

#

.31× .- ×10− 3

 (1) 1

# -0.$ & -10.$ (;) 1  Mark conseq on moles  Note

Ii&- !i&- penalt. B appl. once i! sin&le s! &iven unless calc works eactl. [11]

9.

 %0eal &as equation equation p # n (1) 103000 × 12' × 10 −6 (.31 × -1$) 6alculation 6alculation n # p/ # (1) mark !or volume conversion !ull. correct   &3

# 3.'% < 10  (mol) (1)  :#

 :#

ran&e #-+J H 17  to #-C H 17  &3

!r  # m/n # .30-/3.'% < 10  # 0.1 (1) ran&e C7 : C7-# min 2 s-!- conseq  %! ‘’ wron& lose M2E M2E ‘p’ wron& lose M#E M#E ‘inverte0’ lose M#

$

an0 M4 [5]

 1.

(a)

!1 8 b, mass of 5 # '.'(0)8  (1)

!2 mol  # %2.3 / 12 # '.6% (1) !3 (ratio 11

∴)

mol 5 # '.'0 / 1 # '.'0

5

''

'

Credit variations for M2 78 × 100  = 6 and 12 Correct answer = 3 marks

×

%2.3 100  = 6

' (b) (b)

(5 (5 has has empi empiri rica call mas masss of of 13 13 and and 13  # 6 ∴) 656 Correct answer 1 mark

[4]

 11.

23

23/6.023 < 10 (1) 6*  7 i! inverte0 or multiplie0   &23

tied to !1 3.(2) < 10

2=$ sig figs+ (1) 2 [2]

 12.

(a) (b)

(simplest) ratio of atoms of each element in compound (1) 8 o,gen # 3%.$8 (1)  4a 2.-/23

r 32.1/$2 " 3%.$/16 (1) # 1.23 # 0.61' # 2.-' (21-) so empirical formula # 4a 2r"- (1)  %! 5 o.&en not calculate0 onl. onl. M2 availaleE i! A r  values wron& onl. M1 availale [4]

(a)

13.

0×240 (1)

!r (i1-) # 1%0 (1)

0 ⋅ 2moles i1- #

-

# 0×06 (1)

mass # 0×06 < 1%0 # 11×- (1)

(b)

-

moles 4a"5

# moles 5l # 0.12 (1)

moles # conc  (1)

vol 4a"5

0 ⋅ 12 3 # 1 ⋅ 1 # 10%cm  (1) 3

moles 51 (c )

moles 52

 #

2

 # 0×06 (1)

(allow conseq) conseq)

n93   

#

 p

 ,  #  # n93   (1) or  , 

0 ⋅ 06 ×  ⋅ 31 × 2%3 #

% 000  &3

 (1) 3

# 1×-% < 10  m (1)etc (if chemical error on moles 5 27 ma2) (2)

[11]

10

10.0 14.

(a)

moles of B # 32.1 ( # 0.312$)

allo 32 (1)

mass of sodium sulphide 0.312 < '.1 i.e. 2-.- g or 2-.3' g (accept 2-.3 g or 2-.33 g) (no sig.fig. penalt,) (ignore units) (1)

2

$.00 (b) (b)

mole moless of of h,dr h,drog ogen en sulp sulphi hide de

3-.1

(i.e. 0.1-66 or 0.1-' mol) (1)

moles of h,drogen gas needed # moles of 5 2B (1) volume 0.1-66 0.1-66 < 2-$00 i.e. 3$%2 or 3$%0 3$%0 cm (3602 or 3600 if 0.1-' used) (1)

3

3 3

anser must be in cm  ie < 2-$007 not < 2-.$ / no s.f.  penalt, / ignore units allo ,  allo ,  #  # n93  method  method ith remembered value of 9 of  9 [5]

(a)

15.

Ideal gas equation law (1)

n  = (b)

 Moles o!  X 

 , 

1

110000 × 2.3- × 10

 93  (1) !

-

−

.31 × -'3  &3

# 6.$$ < 10  (1)  !3

65 to 66 × 10

n  = $f write

 " min 2 si# fi#s

 93   ,   %ero &ere" '(t can score M r  m

 9elative molecular mass o!  X  !r  #

n

(1)

 # 62 (1) 615 to 625

 (c)  (c)

8 o o,gen # $1.6 (2)  #3.' / 12

5 # %.6 / 1

" # $'.6 (2) / 16

# 3.23

# %.6

# 3.23

1  3 1

∴

(1)

53" (1)

$f no ) * or if wron# + r  (sed t&en ma, 1 Correct em-irica. form(.a earns a.. t&ree marks

3

62 (d)

( 31  < 53") # 256"2 (1)

1 [/]

mass 16.

(a )

!oles 5l #

1%.6

! r 

 # 36.$ (1) (# 0.$3') 0.$3'

oncentration # 0.2$ (1)  &3

# 2.1$ (mol dm ) (1)

mass !

r   correct Conse on min 2 d- 214 to 215 $#nore (nits + .ose one mark

3

21.'

(b)

×

1000

(i)

0.263

 –3

 = 5.7(1) × 10  (mol) (1)

 !3

57 to 571 × 10

$.'1 × 10

3

−

 &3

2

(ii)

 # 2.$ < 10  (mol) (1)

Conse

0.3%(iii)

2.$ × 10 −3  # 13 (1) Conse

(iv)  9elative atomic mass o!  M  13 = 60 # ' (1) ' 2  ! 3% (1) *

 %0enti!. o!  M  otassium or ; or ;  (1) Conse $f 78 = M r  t&en M = se.eni(m

6 [/]

1.00' 17.

(a )

C # 1.6'3- × 10

mass of 1 mol −

2-

(1) or mass of 1 atom m(st s&ow workin#

# 6.022$ < 10

23

(1) $#nore wron# (nits  answer on. scores 1

2

(b)

e:ual (1) *r same or 11

1  ,1 

(c )

 # n (or n #  93  ) (1)

%000 × 0.03$2 #

.31 × 2%

 (1)

# 1.3% (1) +..ow 13/0 to 13/5 i#nore (nits even if incorrect answer = 14 .oses .ast mark

3

1000 (d)

 &3 0.'32 < 2$0  # 2.%3 (1) mol.dm  (1)

3

 !1

* M" mo.dm " mo.. a..ow 2/28 to 2/3

ote (nit mark tied to c(rrent answer '(t a..ow (nit mark if answer = 2/ or 3

2

2$ (e )

(i)

moles 52B"- # 1000  < 1.2- # 0.0310 $f (se m1v1 = m2v2 scores 3 if answer is correct ot&erwise %ero 3

moles 453 in 30. cm  # 0.0310 < 2 # 0.0620 (1) Mark is for ×2 C if × 2 not (sed

1000 3  &3 moles of 45 3 in 1 dm  # 0.620 < 30.  # 2.01 (1) (mol dm )

+..ow 2010 to 2015 o (nits *" wron# (nits .ose .ast mark

(ii)

moles (45-)B"- # moles 52B"- # 0.310 (1) +..ow conse(entia. wron# mo.es in -art 9i: if c.ear ; 2<*4=9;4:<*4 ron# form(.a for 9; 4:<*4 C=0

!r  (45-)B"- # 132.1 (1) +..ow 9132:

mass # moles < !r  # 0.0310 < 132.1 # -.10 (1) "# $o%&' o# (NH4)SO4 o *%&+r CE 9#: wron# (nit .oses mark +..ow 40/ ! 41 ! 411

6

(f)

!g3 42 * 652" → 3!g("5)2 * 245 3 >orm(.ae 91: a.anced e(ation 91:

2 [16]

average mass of an entit, (1) mass of 1 atom of  12 

(a)

18.

 × 12 (1)2

(b)

simplest ratio of atoms of each element in a compound

(c )

(i)

1

8" # 6$.' (1)

32.% 1.-0 6$.'   1 16 (1) 5" # 12 # 1.%6 1  2.%3 # 2 5"3 (1) (ii)

- 52 "6 (1)

mass ! r  (d)

=

-

1000 16 (1) # 62.$ (1)

(i)

7-72F scores one

(ii)

p# n (1) (1)

n93 

=

2 × 62.$ × .31 × 2% 100000

 #  ,  1 0 m

(1)

3

# 3.

(1)

(allow consequential markin& ut i! !actor o! 2 in missin& ma  2)

6 [13]

Avogadro’s number of molecules (1)

19.

2#

allow  to -1 H 17  molecules "9 No- o! atoms in 12& o!

12

6 

1

 [1]

2.

(a ) 1 (b)

Avogadro’s (i)

p#n (1)

n93 

m

allo D#  ,   etc.7 p#  Mr  

n93  (ii)

#  , 

1 ×  ⋅ 31× 2% #

100 000

# 0.02-

(1) 3

m (1)

(allow 7-724+ to 7-72F) allow use us e o! 177 !or !o r , i! ans &iven & iven as 24-C 2 4-C 0m

#

 p n#  # $00000 × 0.00$

(iii)

.31 × 2'3

(1)

s

9treat 500 as +!1 ot&er va.(es .  2mar  st

00051000 .oses 1  two marks

# 1.10mol (1) (allow 1-1 to 1-11) !r ("2)

# -- (1)

treat wron# Mr as +!1

mass

# --<1.10 # -.$ (g) (1)

(allow 4C:4J)  , 11 1 3 st 9note can (se ca.c(.ation invo.vin# 3   and 224 dm  instead of 1  mark ? re(ires same acc(rac for f(.. marks:

'

100 (c )

# 1000  < $.0 # 0.$(0)(mol) (1)

moles 51

moles 51 moles 52

#

2

(1) # 0.2$ (mol)

9if no factor of 2 C = * from &ere:

mass 52 (d)

(i)

%"

# 0.2$<2 # 0.$(0) (g) (1) 3 # --.- (1)

9if incorrect 9if

*" +!1:

* omitted can score ma, 1 for >eC 2:

3.% ratio >eC* = $$. 

16.' --.9or 50:

12.0  16.0  9if (se +t" C:  # 1  2  Ee 2 "- (1)

(ii)

" (1) 9mark inde-endent of d 9ii::

[15]

20.0 21.

(a )

# 1'.0 (1)

moles of 453 moles of 54" 3

# moles of 453 # 1.1

1.1 volume

# 3

# 0.$ (1) dm (1)

(b)

(i)

(1)

-



n

2

# n (1)



%$000 × 0.0$00

#   #

.31 × 2%

(1)

# 1.%2 mol (1)

1.%2 (ii)

1.$ (1) 1.2 mol

 Moles o! ammonium nitrate  Mass o! ammonium nitrate

mass # 1.2 < 0 (1) # 102 g (1) 6 [10]

12 1.%% × 10 & 23 1+  # 6.03<1023 (1)

22.

2 [2]

(a)

 23.

mass ratio of "2;l"3 # %6 / 2-$.2 ( # 0.3%2)  &2

or moles of " 2 # 3/2 < 1.20 < 10  or e:uivalent (1)

mass of "2 ! 0.3%2 < 1.-' # 0.$'6g (1)  (b  (b)

2

moles "2 ! 1.00/2-.00 ( # 0.0-1' mol) (1) moles ;l"3 # 2/3 moles " 2 # 0.0-1' < 2/3 # (0.02' mol) (1) mass ;l"3 # 0.02' < 122.6 # 3.-lg (1)

3

give one mar for p  for  p  # n93  # n93 to get n for " 27 then second and third mar as above or

2/3 mole of ;l" 3 → 1 !ole of " 2 (1) 3

1.'g → 2- dm  "2 (1) 1.' 2-

3

g # 3.-lg → 1 dm  "2 (1)

 penalise other than 2 & $ sig. figs. once in (d)(i) and (ii)  penalise missing or rong units once in (d)(i) (d)(i) and (ii) [5]

24.

(a) (a)

!ass !ass of of each each elem elemen entt in the the com compo poun und d (1)

1

(b) (b)

4umbe 4umberr of atom atomss of eac each h elem elemen entt in a mole molecu cule le (1)

1

(c )

(i)

!r Fa(4"3)2 # 261 (1)

$ moles Fa(4"3)2 # 261 (1) # 0.01%2 1

moles gas # 2  2  < 0.01%2 (1) # 0.0-'% n 0.0-'% × .31 × 2%  p 100000 # (1) #  &3

3

# 1.1% <10  m (1) (ii) (ii)

moles les 5l 5l # 2 < 0.01 0.01%2 %2 (1) # 0.030.03vol 5l #

1 .2

3

3

 # 0.032 dm (1) (or 32 cm )

' [/]

25.  percentage b, mass of o,gen # 3.08 3.08 (1) ratio of elements # -2.%/12  2.-/1  16.'/1-  3.0/16 (1) # 3.6  2.-  1.2  2.empirical formula is  352 4"2 (1) molecular formula is  65- 42"- (1)

[4]

26.

(a)

85 # 1. (1) 1.2 1. F  5 # 10.  1

(1)

# 2  $  F 25$ (1)

(b)

F-510 (1)

[4]

27.

(a)

mean mass of o f an entit , (or molecule) molecu le) (1) < 12 (1) mass of 1 atom of

12



2

12 (b)

1.%%3 × 10 & 23

#

6.02 < 10

23 (1)

(allo 6.020 to 6.023)

1 [3]

 28.

(b)

(i)

8E

# -2× (1)

GE

$' ⋅ 2

-2 ⋅ 

# 12'  #

1%

(1)

# GE$ (1) (ii)

G2 * $E2 → 2GE$ (1) (o  (or < @)

 [4]

29. C 22.2412 = 1.!5 " 3.711 = 3.71 #$ 74.057%.% = 0.%27 (1) $atio C&"&#$ = 2&4&1 ∴C2"4#$ (1) em'i$ial mass = 107.% ∴ mol o$mula = 215.!107.% × C 2"4#$ = C4"!#$2 (1) must use 8 to Hustif, anser 

or  (22.2-/100) < 21$. # -'.%% i.e. -/12 # - carbon atoms (1) 5 (3.'1/100) < 21$. # .01 i.e. /1 #  h,drogen atoms atoms (1) Fr ('-.0$/100) < 21$. # 1$%. 1$%. i.e. 1$%./'%.% # 2 bromine bromine atoms (1)

or  (-/21$.) < 100 # 22.2-8 (1) 5 (/21$.) < 100 # 3.'1 8 (1) Fr (1$%./21$.) < 100 # '-.0$8 '-.0$8 (1)

3  [3]