The salt copper(II) sulfate dissolves in water according to the reaction: CuSO4(s) Cu2+(aq) + SO42-(aq) (a) Calculate the standard enthalpy change ΔH° for this reaction, using the following data: CuSO4(s) = -771.4 kJ mol-1 Cu2+(aq) = 64.8 kJ mol-1 SO42-(aq) = -909.3 kJ mol-1 kJ (b) Calculate the temperature reached by the solution formed when 13.0 g of CuSO4 is dissolved in 0.109 L of water at 25.0 °C. Approximate the heat capacity of the solution by the heat capacity of 109 g of pure water (specific heat capacity = 4.18 J g-1 °C-1), ignoring the mass of the salt. °C (c) Heats of reaction find practical application in hot packs or cold packs. Would this dissolution reaction be appropriate for the preparation of a hot pack or a cold pack?

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Answer:

(a) [tex]\Delta H=-73.1\frac{kJ}{mol}[/tex]

(b) [tex]T_2=38.1\°C[/tex]

(c) Yes, it is appropriated.

Explanation:

Hello.

(a) In this case, given the formation enthalpies for copper (II) sulfate, copper (II) ion and sulfate ion, we can compute the enthalpy change for such process as follows:

[tex]\Delta H=\Delta H_{Cu^{2+}}+\Delta H_{SO_4^{-2}}-\Delta H_{CuSO_4}\\\\\Delta H=64.8-909.3-(-771.4)\\\\\Delta H=-73.1\frac{kJ}{mol}[/tex]

(b) In this case, since 13.0 g of copper (II) sulfate (molar mass: 159.55 g/mol) we can compute the gained heat by water via:

[tex]Q_{water}=-n_{CuSO_4}\Delta H=-13.0g*\frac{1mol}{159.55g}* -73.1\frac{kJ}{mol}\\ \\Q_{water}=5.96kJ=5960J[/tex]

As the heat lost by the reaction is gained by the water, therefore, the final temperature is:

[tex]Q_{water}=m_{water}Cp_{water}(T_2-T_1)\\\\T_2=T_1+\frac{Q_{water}}{m_{water}Cp_{water}}\\ \\T_2=25.0\°C+\frac{5960J}{0.109L*\frac{1000g}{1L}*4.18\frac{J}{g\°C} } \\\\T_2=38.1\°C[/tex]

(c) In this case, since this dissolution reaction is exothermic as it increases the temperature when undergone, we can infer that yes, this dissolution would be appropriate for the preparation of a hot pack, because a cold pack would be with an endothermic dissolution reaction.

Best regards.