Section 5.2: Calorimetry and Enthalpy Tutorial 1 Practice, page 297

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1 Sectio 52: Calorietry ad Ethalpy Tutorial 1 Practice, page Give: V 60 L ; T iitial 25 C ; T fial 75 C; d H2O(l) H2O(l) 100 g/l Required: theral eergy required, q Aalysis: q cδt Solutio: Step 1: Deterie the ass of water, Vd 100 g 60 L 1 L 60 g Step 2: Deterie the chage i teperature, ΔT Δ T T T fial iitial 75 C 25 C c 418 J/(g C) ; H2O(l) Δ T 50 C Step 3: Calculate the quatity of theral eergy, q q cδt 418 J (60 g ) (50 C ) g C q 13 kj Stateet: The quatity of theral eergy required is 13 kj 2 Give: ethylee glycol 40 kg ; c ethylee glycol 35 J/(g C) ; q 250 kj Required: chage i teperature, ΔT Aalysis: q cδt Solutio: Step 1: Covert quatities to the appropriate uits 3 40 kg g q 250 kj 250!10 3 J Step 2: Rearrage q cδt to ve for ΔT q cδt q Δ T c J 3 35 J (40 10 g ) g C Δ T 18 C Stateet: The teperature chage of the utio was 18 C Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-1

2 3 Give: V HCl(aq) 500 L ; V NaOH(aq) 750 L; T iitial 202 C; T fial 256 C Required: quatity of eergy trasferred, q Aalysis: q cδt Solutio: Step 1: Deterie the total volue of HCl(aq) ad NaOH(aq), V V V + V HCl(aq) NaOH(aq) 500 L L V 1250 L Step 2: Deterie the total ass of two utios, Sice the utio cotais dilute HCl(aq) ad NaOH(aq), the desity ad heat capacity are assued to be the sae as those for water Vd 100 g 1250 L 1 L 1250 g Step 3: Deterie the chage i teperature, ΔT Δ T T T fial iitial 256 C 202 C Δ T 54 C Step 4: Calculate the quatity of eergy trasferred, q q cδt 418 J (1250 g ) (54 C ) g C q 2800 J Stateet: The quatity of eergy trasferred is 2800 J, or 28 kj Sice the teperature of the surroudigs (liquid water i the calorieter) icreased, the reactio was exotheric Mii Ivestigatio: Theral Eergy Trasfer i a Coffee-Cup Calorieter, page 297 Aswers ay vary Saple aswers: ass of water i calorieter g ass of aluiu block 8980 g teperature of aluiu block teperature of hot water bath 800 C fial teperature of water i calorieter 278 C iitial teperature of tap water 198 C A Give: g ; T iitial 198 C; T fial 278 C Required: quatity of theral eergy gaied by the water, q Aalysis: q cδt Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-2

3 Solutio: Step 1: Deterie the chage i teperature, ΔT Δ T T T fial iitial 278 C 198 C Δ T 80 C Step 2: Calculate the quatity of theral eergy gaied by the water, q q cδt 418 J (10000 g ) (80 C ) g C q 3300 J Stateet: The quatity of theral eergy gaied by the water is 3300 J, or 33 kj B Give: Al(s) 8980 g; T iitial 800 C; T fial 278 C ; c Al(s) 0900 J/(g C) Required: quatity of theral eergy trasferred to or fro aluiu, q Aalysis: q cδt Solutio: Step 1: Deterie the chage i teperature, ΔT Δ T T T fial iitial 278 C 800 C Δ T 522 C Step 2: Calculate the quatity of theral eergy trasferred to or fro aluiu, q q cδt 0900 J (8980 g ) ( 522 C) g C q 4220 J Stateet: Sice the value of q is egative, eergy is trasferred fro aluiu to water, ad the quatity trasferred is 4220 J, or 422 kj C Aswers ay vary Saple aswer: There is a differece of about 09 kj i the aswers to A ad B The differece could be due to assuptios or experietal errors D Aswers ay vary Saple aswer: Experietal errors iclude theral eergy lost to the togs, to the air o trasfer fro hot to cold water, to the theroeter, to the calorieter, or to the air above the water aluiu ixture The ivestigatio could be iproved by takig ito accout the teperature chages ad thus eergy trasferred to the theroeter, togs, ad calorieter Other iproveets would be icreasig the isulatio of calorieter ad faster trasfer fro hot to cold water Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-3

4 Tutorial 2 Practice, page Give: 500 g ; Δ H 440 kj/ol H2O(l) Required: ethalpy chage, Aalysis: Δ H Δ H Δ H Solutio: Step 1: Calculate the aout of water i 500 g, M 1802 g/ol M 500 g 1802 g/ol ol (2 extra digits carried) HO(l) 2 Step 2: Solve for the chage i ethalpy, Δ H Δ H HO(l) ΔH kj (27747 ol ) 1 ol Δ H 122 kj Stateet: The ethalpy chage expected whe 500 g of water orizes is 122 kj 2 Give: Na 2SO4g 10H2O(l) 250 kg; Δ Hr 780 kj/ol Required: ethalpy chage, Δ H Aalysis: Δ H ΔH Na2SO4g 10H2O(l) r Solutio: Step 1: Calculate the aout of salt i 250 kg, Na2 SO 4 i10h 2 O(l) M Na2 SO 4 i10h 2 O(l) g/ol Na2 SO 4 i10h 2 O(l) Na 2 SO 4 i10h 2 O(l) M Na2 SO 4 i10h 2 O(l) Na2 SO 4 i10h 2 O(l) 250!103 g g/ol ol (2 extra digits carried) Step 2: Solve for the chage i ethalpy, Δ H!H!H Na2 SO 4 i10h 2 O(l) r # "780 kj & (77582 ol ) $ % 1 ol ' (!H "605 kj Stateet: The chage i ethalpy whe 250 kg of Glauber s salt eters the id state is 605 kj Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-4

5 3 Give: Δ H 1000 kj ; Δ H 157 kj/ol Required: ass of propae, Aalysis: Δ H Δ H Solutio: Step 1: Rearrage Δ H ΔH ΔH Δ H Δ H Δ H to ve for the aout of propae, 1000 kj 157 kj /ol ol (2 extra digits carried) Step 2: Covert aout of propae ito ass, M 4411 g/ol M M 4411 g (63694 ol ) 1 ol CH (l) 281 g 3 8 Stateet: The ass of propae that would orize as a result of absorbig 1000 kj of eergy is 281 g 4 Give: 400 g ; V 1000 L; Δ T 106 C Required: olar ethalpy of disutio, Δ H Aalysis: q cδt; Δ H Δ H Solutio: Step 1: Deterie the ass of water, Vd 100 g 1000 L 1 L 100 g Step 2: Deterie the quatity of theral eergy absorbed by the water, q q cδt 418 J (100 g ) (106 C ) g C q J (2 extra digits carried) This is the quatity of eergy released, Δ H, whe 400 g of is disved Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-5

6 Step 3: Covert ass of ito aout, M 4000 g/ol M 400 g 4000 g/ol 0100 ol Step 4: Rearrage Δ H Δ H to ve for the olar ethalpy of disutio, Δ H Sice eergy is released, Δ H for the reactio is egative; Δ H J Δ H ΔH ΔH Δ H J 0100 ol Δ H J/ol Stateet: The olar ethalpy of disutio of sodiu hydroxide is J/ol, or 443 kj/ol Tutorial 3 Practice, page (a) Solutio: Step 1: Write the balaced cheical equatio without the eergy ter 2 C 2 H 2 (g) + 5 O 2 (g) 4 CO 2 (g) + 2 H 2 O(g) Step 2: Write the balaced cheical equatio for the cobustio of 1 ol C 2 H 2 (g) C 2 H 2 (g) O 2(g) 2 CO 2 (g) + H 2 O(g) Step 3: Sice the ethalpy chage has a egative value, the cobustio reactio of ethye is exotheric Sice a exotheric reactio releases eergy, place the eergy ter o the right side of the equatio C 2 H 2 (g) O 2(g) 2 CO 2 (g) + H 2 O(g) kj Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-6

7 (b) Draw the reactio coordiates with the x-axis labelled Reactio progress ad the y- axis labelled Potetial eergy, Ep (kj) Sice the reactio is exotheric, the products will have lower potetial eergy tha the reactats Poit the arrow fro reactats dowward to products Write the reactats o the upper left-had side of the graph ad the products o the lower right-had side of the graph Iclude the ΔH of the reactio This process is cobustio, so ΔH is ΔH c 2 (a) Sice the teperature of the surroudigs decreases, the reactio is edotheric (b) Draw the reactio coordiates with the x-axis labelled Reactio progress ad the y- axis labelled Potetial eergy, Ep (kj) Sice the reactio is edotheric, the products will have greater potetial eergy tha the reactats Poit the arrow fro reactats upward to products Write the reactats o the lower left-had side of the graph ad the products o the upper right-had side of the graph Iclude the ΔH of the reactio This process is disutio, so ΔH is ΔH (c) A therocheical equatio for the reactio is: HO NH 4 NO 3 (s) kj 2 NH 4 NO 3 (aq) 3 (a) The correspodig therocheical equatio for the reactio depicted by the potetial eergy diagra is: C 2 H 5 OH(l) C 2 H 5 OH(g) H 386 kj (b) The correspodig therocheical equatio for the reactio depicted by the potetial eergy diagra is: C 8 H 18 (l) O 2(g) 8 CO 2 (g) + 9 H 2 O(l) H c 5074 kj Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-7

8 + 4 Give: [Ag (aq)] [Cl (aq)] 0100 ol/l ; utio 1000 g; T iitial 226 C; T fial 234 C ; c 418 J/(g C) Required: olar ethalpy of reactio, Δ Hr Aalysis: q cδt; Δ H Δ Hr Solutio: Step 1: Deterie the chage i teperature of the utio, ΔT Δ T T T fial iitial 234 C 226 C Δ T 08 C Step 2: Calculate the quatity of theral eergy for the reactio, q q cδt 418 J (1000 g ) (08 C ) g C q 334 J (2 extra digits carried) This is the quatity of eergy released, Δ H Sice there is a icrease i teperature, the reactio is exotheric, ad Δ H is egative; Δ H 334 J Step 3: Deterie the aout of AgCl(s) fored i the 100 L utio, AgCl(s) AgCl(s) AgCl(s) + Ag (aq) 0100 ol 500 L 1000 L 0005 ol Step 4: Rearrage Δ H r Δ H ΔH AgCl(s) ΔH Δ H r AgCl(s) r Δ H Δ H to ve for the ethalpy of foratio for 1 ol AgCl(s), r 334 J 0005 ol Δ H r J/ol Stateet: The theral eergy that accopaies the foratio of AgCl(s) is J/ol or 70 kj/ol of AgCl(s) fored Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-8

9 Sectio 52 Questios, page Specific heat capacity is the quatity of theral eergy required to raise the teperature of 1 g of a substace by 1 C The specific heat capacity of water, 418 J/(g C), is higher tha that of aluiu, 0900 J/(g C) Whe the sae ass of aluiu ad water were heated to the sae teperature, the water would have ore theral eergy ad take loger to dissipate the excess eergy, whereas aluiu would have less theral eergy ad take less tie to cool dow Therefore, the aluiu foil ca be safely reoved usig your figers, but touchig the iside of the potato results i a serious bur 2 The burig of gaie ito carbo dioxide ad water is a cobustio reactio, which is a exotheric process The syste releases eergy ad the surroudigs absorb eergy Therefore, the sig of q syste is egative (eergy released), the sig for ΔH is also egative (exotheric process), ad the sig of q surroudigs is positive (eergy absorbed) 3 (a) Fro the balaced equatio, the ethalpy chage of 891 kj is for the foratio of 2 oles of water Calculate the ethalpy chage, H, for 1 ole: 891 kj Δ H 2 Δ H 446 kj So, the ethalpy chage for each ole of water fored is 446 kj (b) Fro the balaced equatio, the ethalpy chage of 891 kj is for the foratio of 1 ole of carbo dioxide So, the ethalpy chage for each ole of carbo dioxide fored is also 891 kj (c) Fro the balaced equatio, the ethalpy chage of 891 kj is for 2 oles of oxyge reacted Calculate the ethalpy chage, H, for 1 ole: 891 kj Δ H 2 Δ H 446 kj So, the ethalpy chage for each ole of oxyge reacted is 446 kj 4 Give: 200 g ; Δ H kj/ol ; V 125 L; Δ Tiitial 200 C Required: fial teperature, Δ Tfial c T Aalysis: Δ H Δ H ; q Δ Solutio: Step 1: Covert ass of NH 4 Cl(s) ito aout, M 5350 g/ol M 200 g 5350 g/ol ol (2 extra digits carried) H2O(l) Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-9

Step 2: Calculate the ethalpy chage for the reactio, Δ H ΔH Δ H 148 kj (0373 83 ol ) 1 ol Δ H 55327 kj (2 extra digits carried) Sice Δ H is positive, theral eergy is absorbed fro the surroudigs So,

10 Step 2: Calculate the ethalpy chage for the reactio, Δ H ΔH Δ H 148 kj ( ol ) 1 ol Δ H kj (2 extra digits carried) Sice Δ H is positive, theral eergy is absorbed fro the surroudigs So, the chage i theral eergy of the surroudig water, q, is egative; q kj Step 3: Deterie the ass of water, Vd 100 g 125 L 1 L 125 g Step 4: Rearrage q cδt to ve for the teperature chage, Δ T q cδt q Δ T c J 1 1 (125 g )(418 J g C ) Δ T 106 C Step 5: Calculate the fial teperature, Δ T fial Δ T T T fial fial T Δ T + T iitial iitial 106 C C Tfial 94 C Stateet: The fial teperature observed whe 200 g of aoiu chloride is added to 125 L water at 200 C is 94 C 5 (a) Draw the reactio coordiates with the x-axis labelled Reactio progress ad the y-axis labelled Potetial eergy, Ep (kj) Sice the reactio is edotheric, the products will have greater potetial eergy tha the reactats Poit the arrow fro reactats upward to products Write the reactats o the lower left-had side of the graph ad the products o the upper right-had side of the graph Iclude the ΔH of the reactio This process is foratio, so ΔH is ΔH f Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-10

(b) Draw the reactio coordiates with the x-axis labelled Reactio progress ad the y- axis labelled Potetial eergy, Ep (kj) Sice the reactio is exotheric, the products will have lower potetial eergy

11 (b) Draw the reactio coordiates with the x-axis labelled Reactio progress ad the y- axis labelled Potetial eergy, Ep (kj) Sice the reactio is exotheric, the products will have lower potetial eergy tha the reactats Poit the arrow fro reactats dowward to products Write the reactats o the upper left-had side of the graph ad the products o the lower right-had side of the graph Iclude the ΔH of the reactio This process is cobustio, so ΔH is ΔH c 6 (a) A therocheical equatio for the cobustio for propae is: C 3 H 8 (g) + 5 O 2 (g) 3 CO 2 (g) + 4 H 2 O(l) ΔH 2220 kj (b) A therocheical equatio for the separatio of atos i the chlorie olecule is: Cl 2 (g) 2 Cl(g) ΔH 243 kj (c) A therocheical equatio for the foratio of iro(iii) oxide fro its eleets is: 2 Fe(s) O 2(g) Fe 2 O 3 (s) ΔH 824 kj (d) A therocheical equatio for the decopositio of hydroge chloride ito its eleets is: HCl(g) 1 2 H 2(g) Cl 2(g) ΔH 93 kj 7 (a) A therocheical equatio for the foratio of 1 ol of copper(ii) chloride fro its eleets is: Cu(s) + Cl 2 (g) CuCl 2 (s) kj (b) A therocheical equatio for the coversio of graphite to diaod is: C graphite (s) + 20 kj C diaod (s) (c) A therocheical equatio for the decopositio of silver chloride ito its eleets is: AgCl(s) kj Ag(s) Cl 2(g) Copyright 2012 Nelso Educatio Ltd Chapter 5: Therocheistry 52-11

Section 7.4: Calculations Involving Limiting Reagents

Section 7.4: Calculations Involving Limiting Reagents Sectio 7.4: Calculatios Ivolvig Limitig Reagets Tutorial 1 Practice, page 33 1. Give:.3 mol ;.0 mol HNO = 3 Required: amout of water, NaCO = 3 O H Solutio: Step 1. List the give values ad the required