Mole Exam Mark Scheme

8/11/2019 Mole Exam Mark Scheme

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1.2 PRACTICE EXAMINATION QUESTIONS MARK SCHEME

1. (a) (i) Avogadros number/constant of molecules/particles/species / 6 10 23 1[Not atoms]

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

in 12.(00)g of 12 1

(ii) !oles " 2 # 320.3$0

(# 1.0% 10 &2 mol) 1

# 2% ( 1.0% 10 &2) 1[Accept answers via 4 separate mole calculations]

# 0.316 & 0.31' mol ans er to 3* sf+ 1

[Mark conseq on errors in M1/M2] (1)

(iii) !oles of nitrogl,cerine # - 1.0% 10 &2 (# 0.0-3 mol) 1[Mark conseq on t eir moles o! " 2 ]

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

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

(b) p # n or p # or p #n

1

p # /n

#3101.001100.310. '3

1

# '% 00%3 or '% 0 or '.% 1[i&nore s-!-]

units # a or a or ! a (as appropriate)1

[%! error in conversion !rom ,a treat as a contra0iction o! t eunits mark][%! trans!er 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]


2/17

2.

(a) 4a l"

2321.6

3$.$33.3

16-$.1

1

0.%(3%) 0.%(3 )2. (2)

5ence 11

31

Accept bac ards calculation7 i.e. from formula to 8 composition7and 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 l 2 * 64a"5 $4a l * 4a l" 3 * 35 2" 1[3]

3. (penalt, for sig fig error #1mar per :uestion)

(a) (i) moles ;4" 3 # 1.00/101.1 # %. % < 10=3 (mol) 1

(ii) p # n or n # p / 1

moles "2 # n # 93 p1

# (1) 2%31.1022.1100000 - &

(1) 2

# -.%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 use0 M# M4 7)

(i! wron& temp conversion : lose M# : conseq M4)

(i! n 93/p 6* lose M# an0 M4)

(b) (i) simplest/lo est ratio of atoms of each / element/s in a compound /substance / species / entit, / molecule 1

(ii) ' N "

1.3%%.-$

1-$.16

166.3'

(1)1.1' 1.1 2.3$

1 1 2


3/17

;4" 2 (1)3

(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 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! At N> use0 lose M1 an0 M2) 1

moles !g("5) 2 # 0.01'2 (conse: on rong ! 2) (ans er to 3* s.f.) 1

moles 5 l # 2 < 0.01'2 # 0.03-- or 0.03-3 (mol) (process mark) 1

vol 5 l # 1100003-3.0

# 3-.3 & 3-.$ (cm 3) (unless wron& unit) 1

(i! can0i0ate used 7-71+ or 7-71+1 lose M2)

(?ust answer wit no workin& i! in ran&e (4)- i! sa. #4 t en (2))

(i! not 2@1 ratio lose M# an0 M4)

(i! work on 6l 6* 7/4)[4]

5. 2A1* 3 u l 2

2A1 1 3 * 3 u9(accept multiples/!ractions)

"

2A1* 3 u 2* 2A1 3*

* 3 u9 1

[1]

6. (a) moles 540 3 #1'$ ?

10 &3 < 1.$ # (0.262$ mol)9 1moles b(4" 3 )2 # @

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Mole Exam Mark Scheme