3.4_Thermochem_AS91390

= 3.4 AS91390 Demonstrate understanding of thermochemical principles and the properties of particles and substances (5 credits)=

__ ELECTRON CONFIGURATION OF ATOMS AND IONS __

 * [[image:l3spd.jpg width="258" height="255" link="@http://www.colorado.edu/physics/2000/applets/a2.html"]] || [[image:chemicalminds/l3spd2.jpg width="384" height="227" link="@http://www.fscj.me/e_config/e-1instruct.html"]] ||

NCEA PAST EXAM QUESTION: Write the electron configuration using s,p,d notation for:
====You can be asked to write the electron configuration of atoms and ions for the first 36 elements, so practise, practise these... write down the spd for atoms/ions of your choice and check your answers for the electron configurations of atoms on David Whizzy's Periodic Table====

Account for the difference in atomic or ionic properties given in the table below


**ii)** P atom and P3– ion


__2. Trends in Ionisation Energy __
====Define First ionisation energy: The following table shows the first ionisation energy values for elements in the third period of the periodic table. ==== ====Justify the periodic trend of first ionisation energies shown by the data in the table above, and relate this to the expected trend in atomic radii across the third period. ====

The following table shows the electron configurations of four atoms, He, B, N, and Ne. Arrange these atoms in order of increasing first ionisation energy


A chlorine atom has a greater first ionisation energy than a sodium atom.


ii) With reference to the graph below, discuss the general trends in ionisation energies from lithium to sodium, and account for any anomalies.
Account for the differences in the atomic properties given below

[[image:NCEA 2008.jpg]] A bromine atom, Br, is smaller than a scandium atom, Sc, but its ionisation energy is larger.


**i)** Describe what is meant by “the ﬁrst ionisation energy of chlorine”.
====**ii) ** Place magnesium, calcium and chlorine atoms in order of increasing first ionisation energies (IE). Justify your answer in terms of the factors that affect ionisation energy.====

<span style="font-family: Arial,Helvetica,sans-serif;">Using your knowledge of trends in the periodic table, circle the atom below that has the greater electronegativity value. Justify your answer.
<span style="font-family: Arial,Helvetica,sans-serif;">Br I <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Discuss the data for the following
<span style="font-family: 'Times New Roman','serif'; font-size: 16px; line-height: 0px; overflow: hidden;"> <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

__<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">Summary of Trends in the Periodic Table __

 * [[image:l3trendssummary.jpg width="240" height="168" link="@file:overviewtrends.swf"]] || [[image:chemicalminds/l3trendsvisualsummary.jpg width="320" height="138" link="@file:visualtrends.swf"]] || [[image:PTsummary.jpg width="320" height="96" link="@file:PT of trends.swf"]] ||

Please note: For Excellence answers requiring a discussion of trends be sure to refer to 1) nuclear charge 2) number of energy levels 3) electron-electron repulsion
 * [[image:l3summaryPT1.jpg width="480" height="668" link="@file:summaryperiodictrends.docx"]] || [[image:chemicalminds/l3summaryPT2.jpg width="400" height="433" link="@file:summaryperiodictrends.docx"]] ||

Now, try these quick revision questions on trends in the Periodic table




<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">First, recap on __Lewis structures__

 * [[image:Level3Lewis.jpg width="274" height="171" link="@http://media.wwnorton.com/college/chemistry/chemtours/chapter_08/lewis_structures/Interface.swf"]] || [[image:l3lewis2.jpg width="276" height="224" link="@file:Lewis diagrams.swf"]] ||

<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">Now, view __Shapes of Molecules__ in 3D

 * [[image:level3shapesphet.jpg width="286" height="162" link="@https://phet.colorado.edu/en/simulation/molecule-shapes"]] || [[image:level3shapeswebsite.jpg width="231" height="154" link="@http://cdn.wwnorton.com/college/chemistry/chem3/chemtours/chapter_09/vsepr/index.html"]] ||

<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">iii) state the bond angles

 * =  ||= [[image:l32.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l33.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l34.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l35.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l36.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l37.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l38.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l39.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l310.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l311.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l312.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||
 * = [[image:l313.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||= [[image:l314.JPG width="400" height="300" link="@file:l3summaryshapes.docx"]] ||

Download Powerpoint Level 3 Summary of shapes of molecule




__<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">EXPLAINING SHAPE AND POLARITY OF MOLECULES __
==<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Describing and Explaining shapes and polarity. In your answer, you must make reference to the arrangement of electrons... == <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">
 * [[image:chemicalminds/level3compareshapes.jpg width="279" height="185" link="@file:compare shapes.swf"]] || [[image:l3explainshapewebsite.jpg width="296" height="297" link="@http://www.creative-chemistry.org.uk/molecules/trigbi.htm"]] || [[image:l3explainshapeswebsite2.jpg width="235" height="298" link="@http://www.creative-chemistry.org.uk/molecules/octahedral.htm"]] ||

Indicate the polarity of the following bonds by indicating any dipoles present. F - Cl, At - Cl
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">The Lewis structures for the two molecules PCl3 and PCl5 are shown below. Compare & contrast the shapes & the polarities of these two molecules.
<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">

<span style="font-family: Arial,Helvetica,sans-serif;">The Lewis diagrams for ClF3 and AsF5 are shown below. Compare and contrast the shape and polarity of these molecules.
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 15.3333px;">

The Lewis diagrams for IF 5 and PCl 5 are shown below. Discuss the polarities of these molecules.
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 15.3333px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Discuss the fact that although both SF4and XeF4have four bonds around the central atom, the molecules have different shapes and polarities.
<span style="color: #221e1f; font-family: 'Arial','sans-serif'; font-size: 14.6667px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Compare the polarities of the two molecules, BrF3 and SF6
<span style="font-family: 'Arial','sans-serif'; font-size: 16px;"> ==== **a)** The drawings below are three possible shapes for a molecule ZF 4 , where ‘Z’ represents the central element. ‘Z’ has lower electronegativity than F. Name the shapes represented by the three diagrams. ====

<span style="font-family: Arial,Helvetica,sans-serif;">The Lewis structures for each molecule are shown below.
<span style="font-family: 'Times New Roman','serif';">

<span style="font-family: Arial,Helvetica,sans-serif;">Discuss reasons for the difference in the polarities of BF3 and PF3 molecules.






<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Describing and Explaining Enthalpy changes
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">(ii) Justify your choice.
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Write the equation for the reaction that has an enthalpy change given by Δ fH°(HCl, g).
<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">

**<span style="font-family: 'Times New Roman','serif';">ii) **<span style="font-family: Arial,Helvetica,sans-serif;"> Explain why ΔfH(H2O, ℓ) is equal to ΔcH(H2, g).






<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Enthalpy Change Calculations
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

The melting point of boron is 2300°C.
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">i) Calculate the standard enthalpy of formation of liquid ethanol using the information given above
====<span style="font-family: Arial,Helvetica,sans-serif;">ii) Discuss how the value of the enthalpy change would differ if the ethanol product formed was a gas rather than a liquid. No calculation is necessary. ====

<span style="font-family: Arial,Helvetica,sans-serif;">Δ vap H °(H2O(ℓ)) = + 44 kJ mol–1
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif; line-height: 0px; overflow: hidden;">

<span style="font-family: Arial,Helvetica,sans-serif;">Calculate the energy produced when 50.0 g of ammonia reacts as shown in the equation above.
<span style="font-family: Arial,Helvetica,sans-serif;"> ====<span style="font-family: Arial,Helvetica,sans-serif;">Δ fH°(HBr, g) is –36.2 kJ mol–1. Calculate the heat produced by the formation of 50.0 g of HBr(// g //) from its elements in their standard states.====

__<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">CALORIMETRY __

 * [[image:calorimetry3.jpg width="213" height="216" link="@http://cdn.wwnorton.com/college/chemistry/chem3/chemtours/chapter_05/calorimetry/Interface.swf"]] || [[image:calorimetry.jpg width="295" height="179" link="@http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/heat_metal_ice.html"]] || [[image:chemicalminds/calorimetry2.jpg width="324" height="150" link="@http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/calorimetry.html"]] ||

<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTIONS: Carry out the following questions on Calorimetry
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> ==== **i)** When 25.0 mL of a 1.00 mol L–1 hydrochloric acid solution, HCl, is added to 25.0 mL of a 1.00 mol L–1 ammonia solution, NH3, a temperature rise of 6.50°C is recorded, as a neutralisation reaction occurs to produce aqueous ammonium chloride and water. Calculate Δ r //H// ° for this neutralisation reaction. The mass of the mixture is 50.0 g. Assume specific heat capacity of the aqueous ammonium chloride = 4.18 J g–1 °C–1 ==== ====** ii) ** When the Δ r // H // ° for the neutralisation above was found experimentally in a school laboratory, the value obtained was lower than the theoretical value. Account for the difference in values, and suggest how this difference could be minimised. ====

The theoretical value is –2 058 kJ mol –1 . Account for the difference in values, and suggest how this difference could be minimised.
====<span style="font-family: Arial,Helvetica,sans-serif;">The apparatus below was used to determine the enthalpy of combustion of hexane. When 0.400 g of hexane was burned in the spirit burner, the temperature of 150 g of water was found to increase from 22°C to 39°C. Calculate the experimental value of ΔcH (C6H14, ℓ). SHC of water = 4.18 J g–1 °C–1 ==== ====<span style="font-family: Arial,Helvetica,sans-serif;">Account for the difference between the experimental value and the value given in a data book as ( - 4163kJmol-1) AND suggest how this difference could be minimised. ====

<span style="font-family: Arial,Helvetica,sans-serif;">Dissolving of ammonium nitrate in water is an endothermic process.
<span style="display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">NH4NO3(s) → NH4+(aq) + NO3–(aq) ====<span style="font-family: Arial,Helvetica,sans-serif;">When 1.80 g of ammonium nitrate was dissolved in 50.0 g of water, the temperature decreased by 2.70°C. The heat capacity of water is 4.18 J g–1°C–1 ====

<span style="font-family: Arial,Helvetica,sans-serif;">(ii) Calculate the mass of ammonium nitrate that would be required to absorb 1.25 kJ of energy.
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

====<span style="font-family: Arial,Helvetica,sans-serif;">The diagram below shows a simple calorimeter. It can be used to measure the enthalpy of combustion of ethanol, C2H5OH. If 1.00 g of ethanol is burned in the spirit burner, the temperature of the 200 g of water is found to increase from 22°C to 40°C. ====

<span style="font-family: Arial,Helvetica,sans-serif;">Using these results, calculate the experimental value of ∆cH (C2H5OH, l). Specific heat capacity of water = 4.18 J g–1 °C–1
====<span style="font-family: Arial,Helvetica,sans-serif;">Give two reasons why the experimental value for the enthalpy of combustion of ethanol calculated in part (a) is so much less than the ‘accepted’ value in data books ====



<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Hess's Law Calculations
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

Δf //H// ° (H2O( l )) = −286 kJ mol–1
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> An equation for the reaction of ammonia gas with hydrogen chloride gas is: NH 3 (//g//) + HCl(//g//) → NH 4 Cl(//s//) Calculate the standard enthalpy change, Δ r // H° //, for this reaction, using the following data. Δ f // H° // (NH 3 (//g//)) = –46 kJ mol –1 Δ f // H° // (HCl(//g//)) = –92 kJ mol –1 Δ f // H° // (NH 4 Cl(//s//)) = –314 kJ mol –1 <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> ====<span style="font-family: Arial,Helvetica,sans-serif;">Decane is a component of petrol. Carbon dioxide and water are formed when decane burns completely in oxygen. C10H22(ℓ) + 15 ½ O2(g) → 10CO2(g) + 11H2O(ℓ) ====

<span style="font-family: Arial,Helvetica,sans-serif;">Δf H °(H2O(ℓ)) = –286 kJ mol–1
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">H2O(l) --> H2O(g) H = +41 kJ mol–1
<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Δf H °(H2O(ℓ)) = –286 kJ mol–1
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 10.6667px;"> **a)** The equation for the combustion of ethanol is: C 2 H 5 OH(//ℓ//) + 3O 2 (//g//) → 2CO 2 (//g//) + 3H 2 O(//ℓ//) Calculate Δ c // H // ° (C 2 H 5 OH (//ℓ//)), given the following data:

<span style="font-family: Arial,Helvetica,sans-serif;">H2O(ℓ ) Δf H ° = –286 kJ mol–1
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 10.6667px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Δf H° (SO2(g)) = –297 kJ mol–1
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 10.6667px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Δf H ° (H2O, ℓ) = –286 kJ mol–1
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 10.6667px;">

<span style="font-family: Arial,Helvetica,sans-serif;">H2O(l) → H2O(g) ΔvapH = +41 kJ mol–1
<span style="color: #221e1f; font-family: 'Times New Roman','serif'; font-size: 10.6667px;">

<span style="font-family: Arial,Helvetica,sans-serif;">Δ fH°(H2O, ℓ) = –286 kJ mol–1




<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Predicting Entropy Change
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> ====<span style="font-family: Arial,Helvetica,sans-serif;">Predict the entropy change for each of the following reactions by stating whether the entropy will increase OR decrease. Give a reason for each answer. ====

<span style="font-family: Arial,Helvetica,sans-serif;">iii) N2O4(g) --> 2NO2(g)




<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">[[image:ncea2014.jpg]]
====**a)** Ammonium nitrate is used in ‘cold packs’ to relieve symptoms of a sports injury. The dissolving of the solid crystals of ammonium nitrate (shown in the equation below) is spontaneous, despite being endothermic. Explain why this is so, in terms of the entropy change for the reaction system. ====

Tick to the left of any statement that is correct for the above reaction. Justify your answer.
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

Your answer should consider both enthalpy and entropy changes.
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Explain why this reaction is spontaneous by considering the entropy changes when steam condenses.
<span style="color: #000000; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">if you are interested, download some but not essential information from Chemguide on Entropy



__<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">INTERMOLECULAR FORCES __

 * [[image:l3intermolecular.jpg width="373" height="256" link="@http://cdn.wwnorton.com/college/chemistry/chem3/chemtours/chapter_10/intermolecular_forces/Interface.swf"]][[image:l3hydrogenbonds.jpg width="313" height="195" link="@file:hydrogenbondsinwater.swf"]] ||  ||

<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">NCEA EXAM QUESTION: Relating boiling point to intermolecular forces
<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">(i) List all the forces of attraction between these molecules in each of their liquid states.
====<span style="font-family: Arial,Helvetica,sans-serif;">(ii) Use the information above to explain the difference in the boiling points of pentan-1-ol and dimethylpropan-1-ol by comparing and contrasting the relative strengths of the attractive forces between the molecules involved. ==== <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;"> ====<span style="font-family: Arial,Helvetica,sans-serif;">**1)** The boiling points of ammonia, NH3, fluorine, F2, and hydrogen chloride, HCl, are given in the table below. Complete the table to identify the attractive forces between the molecules in their liquid state. ==== b) ==== **b)** Discuss the differences between the boiling points of NH 3 and HCl, in terms of the strength of the attractive forces between the particles involved. Then describe why F 2 has the lowest boiling point. ====  **2)** <span style="font-family: Arial,Helvetica,sans-serif;">The following graph shows the change in temperature over a five-minute period for a sample of ammonia, where a constant amount of heat was applied per minute. ====<span style="font-family: Arial,Helvetica,sans-serif;">Using the graph above, justify the physical changes occurring to ammonia between points A and D, in terms of the energy of the particles and the intermolecular forces of attraction. ==== <span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">a) Explain why the temperature of liquid water does not change when it is heated at 100°C.
====<span style="font-family: Arial,Helvetica,sans-serif;">b) Use the information in the table above to compare and contrast the boiling points of hydrazine, fluoromethane, and decane in terms of the relative strengths of the attractive forces between the particles involved ====

<span style="color: #f95725; font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Use the information in the table to answer the following question.
====<span style="font-family: Arial,Helvetica,sans-serif;">Compare and contrast the boiling points of water, oxygen, and hydrogen sulfide in terms of the similarities and differences in the relative strengths of the attractive forces present between particles. ==== <span style="font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Identify the substance with the higher boiling point, and justify your choice.
<span style="color: #211d1e; font-family: 'Times New Roman','serif'; font-size: 16px;">

<span style="font-family: Arial,Helvetica,sans-serif;">• compare the boiling points of H2S, H2Se and H2Te, and explain the observed trend in terms of bonding AND mass.
<span style="font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Identify the types of intermolecular forces for each of these substances and explain why ethanol has a higher boiling point than propane.
<span style="font-family: Arial,Helvetica,sans-serif;">b) Account for the difference in the boiling points of the two substances in the table below by comparing **all the intermolecular forces**.

<span style="font-family: Arial,Helvetica,sans-serif;">

Justify the similarity in the Δ vap // H // ° of CH 3 Cl and CH 3 NH 2.
====<span style="font-family: Arial,Helvetica,sans-serif;">Account for the difference in the boiling points for the following pairs of compounds by comparing the main forces between the molecules in each case. ====

<span style="font-family: Arial,Helvetica,sans-serif;">Use the following information to answer the question below.
====<span style="font-family: Arial,Helvetica,sans-serif;">Discuss the trend in DvapH of the compounds in the table above in terms of the attractive forces between the particles and the factors affecting those forces. ==== ====<span style="font-family: Arial,Helvetica,sans-serif;">Discuss the nature of the forces between molecules in each of the three substances given in the table below, and account for the variation in the melting points. ====



<span style="font-family: Arial,Helvetica,sans-serif;">**(a)** Describe what is meant by the term DfusH  °.
====<span style="font-family: Arial,Helvetica,sans-serif;">**(b)** A knowledge of the nature of the substances in the table would indicate that the row of data for one of the substances is obviously incorrect. ====

<span style="font-family: Arial,Helvetica,sans-serif;">Name this substance.
====<span style="font-family: Arial,Helvetica,sans-serif;">Discuss the nature of bonding in the substances named in the table above, and hence clearly explain why the row of data values can be identified as incorrect. ====



**"Atom Bond - The atom with the golden electron"**
====In this award-winning animated parody of a James Bond movie, special agent Gold Metallic Bond investigates why Carbon, Nitrogen and other atoms are training themselves in other types of bonds. He uncovers their bond school, learns that they are working towards Project D and ends up being shown around a giant DNA. The cliches and puns from the bond movies are used to bring to life topics including different types of bonding, how and why different atoms bond together, and the results of atoms bonding.==== media type="custom" key="26213038" align="center"



<span style="color: #f95727; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">Download this FREE preview of a SUPERB Level 3 Chemistry workbook <span style="color: #f95727; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">Continuing Chemistry (2013) Anne Wignall and Terry Wales, Pearson Publishers <span style="color: #f95727; display: block; font-family: Arial,Helvetica,sans-serif; text-align: center;">Answers included at the back of the book too (Thank you!) <span style="color: #f95727; display: block; font-family: Arial,Helvetica,sans-serif; line-height: 0px; overflow: hidden; text-align: center;">