Enthalpy (Heat) of Solution for the Dissolution of a Salt Maw of salt (g) Moles

ID: 975313 • Letter: E

Question

Enthalpy (Heat) of Solution for the Dissolution of a Salt Maw of salt (g) Moles of salt (mol) Mass of calorimeter (g) Mass of calorimeter + water (g) Mass of water (g) Initial temperature of water (degree C) Final temperature of mixture from graph (degree C) Instructor's approval of graph Calculations for Enthalpy (Heat) of Solution for the Dissolution of a Salt Temperature change of solution. Delta T (degree C) Heat change of water (J) Heat change of salt (J) (Obtain its specific heat from Table 25.1.)* Total enthalpy change (J) Delta H, (J/mol salt), equation 25.12 Average Delta H, (J/mol salt) Show calculations for Trial 1. Report the result with the correct number of significant figures.

Explanation / Answer

Name of salt

Na2SO4

Molecular weight of salt

142

Tria-1

Trial-2

Moles = Mass/Molecular weight

= 5.137/142=0.03617

=5.070/142=0.0357

Temperature drop, deg.c

=24.8-23.7= 1.1

=25.8-24.1=1.7

Mass of water (g) = mass of calorimeter+water- mass of calorimeter

37.889-18.688=19.201gm

35.990-14.638=21.352

Heat change Joules= mass* specific heat* temperature difference,

Specific heat of water= 4.18 j/deg.c

19.201*4.18*1.1 =88.28

21.352*1.7*4.18=151.73

Specific heat of salt (J/mol.K)

128.2

Heat change

=128.2*0.03617*1.1=5.1

=128.2*1.7*0.0357=7.78

Total heat change, joules

=88.28+5.1=93.38

151.73+7.78=159.51

Enthalpy change/mole of salt

Joules/mole

93.38/0.03617=2581.7 Joules

159.51/0.03617=4410

Average enthalpy change J/mole

=(2581.7+4410)/2 = 3496