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2SUPERVISOR’S USE ONLY

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© New Zealand Qualifications Authority, 2017. All rights reserved.No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority.

ASSESSOR’S USE ONLY

TOTAL

Level 2 Chemistry, 201791164 Demonstrate understanding of bonding,

structure, properties and energy changes

2.00 p.m. Thursday 16 November 2017 Credits: Five

Achievement Achievement with Merit Achievement with ExcellenceDemonstrate understanding of bonding, structure, properties and energy changes.

Demonstrate in-depth understanding of bonding, structure, properties and energy changes.

Demonstrate comprehensive understanding of bonding, structure, properties and energy changes.

Check that the National Student Number (NSN) on your admission slip is the same as the number at the top of this page.

You should attempt ALL the questions in this booklet.

A periodic table is provided on the Resource Sheet L2–CHEMR.

If you need more room for any answer, use the extra space provided at the back of this booklet and clearly number the question.

Check that this booklet has pages 2 –12 in the correct order and that none of these pages is blank.

YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.

Merit

15

QUESTION ONE

(a) When solid calcium chloride. CaC14s). reacts with water. the temperature increases.

Circle the term that best describes this reaction.

Give a reason for your choice.

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(b) When a person sweats. water is lost from the body by evaporation. This is an endothermicprocess. This evaporation speeds up when a person exercises.

(i)

(ii)

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Explain why the evaporation of water in sweat from the body is endothermic. and whyexercise increases this evaporation..fi

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Draw a labelled enthalpy diagram for the evaporation ot‘water. HZOU").

H20({’) —> H2O(g) ArHO —— 40.7 kJ mol’1 _

—)

Enthalpy

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Chemistry 91164, 2017

3

finfifimeUSE ONLY(iii) Sodium chloride, NaCl, is another compound that is excreted from the body in sweat.

Use your knowledge of structure and bonding to explain the diSSOIVing Process Ofsodium chloride, NaCl, in water.Support your answer with a labelled diagram.

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acts with a metal powder.(e) 'l‘hcrmitc reactions occur when a metal oxide rc-

Thc equations for two thermite reactions are given below:

Reaction 1: F8203(S) + 2A|(S) -> 2Fe(5) + Al203(s)Reaction 2: 3CUO(S) + 2AI(S) —-> 301(3) + A|203(S)

ArH° = —852 kJ mol‘1

ArH° = —1520 kJ mol‘1

1362030), or copper(II)l oxide is reacted withUse calculations to determine which metal oxide, iron(III) oxide,

oxide, Cu0(s), will produce more heat energy when 50.0 g of eaCh metaaluminium powder, Al(.s').

Mvr(rcur»ro‘):7/9,6 g. mol‘1

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QUESTION TWO ASSESSOR'SUSE ONLY

(a) (1') Draw the Lewis structure (electron dot diagram) for the following molecules, and nametheir shapes.

Approximate. <bond anglearound thecentral atom

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Chemistry 91164, 2017

6

ASSESSOR'SUSE ONLY

(b) Three-dimensional diagrams for two molecules are shown below.

Molecule

(i) In the boxes above. identify the polarity of each molecule. by miting either polar ornon-polar.

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(C)

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LReaction N2H4(g) + 02(9) —» N2(g) + 2H20(g)

llydrazine. NzH4. is used as rocket fuel.

Use calculations to determine which of Reaction 1 or Reaction 2 releases more magiA

/’\i

/.Reaction 2." N2H4(Q) + 26(9) -* N2(9) + 4HF(9)

The structure of each chemical species is shown in the box below.

[::HH\ /N — N/ \

H Hhydrazine

H —O—Hwater

O=Ooxygen

F-Ffluorine

N—=Nnitrogen

H—Fhydrogen fluoride

Use the average bond enthalpies given in the tab e below.1

Bond Average Bond enthalpy Bond Average Bond enthalpy/kJ mol‘1 /kJ mol‘1

Show your working and include appropriate units in your answer.R: .— (:38 + tram) may) 4% + Mars) :is‘sn'

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Chemistry 91164, 2017

QUESTION THREE

(a) (‘omplete the table belou by statintU the type of solid. the type of particle. and the t} pe ofbonding (attractiVe forces) between the particles in each solid. 4' ""T

Type of solid Type of particle Attractive forcesbetween particles—_\ [

Solid

—|1—Al(s) /

(aluminium) I {l’le

MgCl2(s)(magnesium chloride)

S8(8) ’y'(sulfur)

A|(s)

Justify" your choice. referring to the attractive forces between the particles ol‘ALL threesubstances.

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Question Threecontinues on thefollowing page.

Chemistry 91164. 2017

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10

CW.”Circle the substance which is malleable.

MgCl2(s) 88<s>Justify your choice by referring to the structure and bonding ofyour chosen substance.

You may include a diagram or diagrams in your answer.

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Extra paper if required.Write the question number(s) if applic/able.

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QUESTIONNUMBER

Chemistry 91164, 2017

91164

QUESTION 1NUMBER “

12

Extra paper if required.Write the question number(s) if applicable.

Chemistry 91164, 2017

ASSESSOR‘SUSE ONLY

   

Subject:   Chemistry   Standard:   91164   Total  score:   15  

Q   Grade  score   Annotation  

1   M5  

This  candidate  received  a  grade  score  of  M5  as  the  response  linked  reaction  processes  to  reaction  progress,  the  attractions  of  water  and  NaCl,  although  without  an  accurate  diagram,  and  correctly  analysed  the  energy  output  of  thermochemical  calculations.  

2   M5  This  candidate  received  a  grade  score  of  M5  as  the  response  linked  electronegativity  to  bond  polarity  and  bond  enthalpies  to  one  correct  enthalpy  change,  although  the  unit  was  incorrect.  

3   M5  This  candidate  received  a  grade  score  of  M5  as  the  response  linked  two  of  the  three  attractive  forces  to  the  energy  requirements  of  melting  while  also  linking  the  malleability  of  aluminium  to  the  non-­directional  nature  of  metallic  bonding.