consider the dissolution of a 1.50g of salt xy ... Question Consider the dissolu

Question

consider the dissolution of a 1.50g of salt xy ... Question Consider the dissolution of a 1.50g of salt XY in 75mL of water within a calorimeter. The temperature of the water decreased by 0.93C. The heat capacity of the calorimeter is42.2J/C. The density of the water (and the solution) is1.00g/mL. The specific heat of the solution is4.184J/gC a). Identify the system; write a reaction that describesthe event occuring in the system b). Which of the following best describes thesurroundings. Explain. -the water alone -the solution alone (dissolved salt and water) -water plus the calorimeter -the calorimeter plus solution c) Determine if the reaction was endothermic orexothermic. Explain d) Determine the quantity of heat gained or lost by thesurroundings. Keep in mind your answers to item b and cabove. e) Determine the enthalpy change, for dissolving thesalt. Report the value as the total energy absorbed orreleased when the entire sample of salt dissolves and then on apergram basis. What additional information would be needed toreport the enthalpy change on a per mole basis?

Explanation / Answer

a) System (the reaction itself, including the reactants and products): XY(s) ----> X(aq) + Y(aq)

b) Surroundings (everything outside the reaction): water and the calorimeter.

       qrxn = -qcal - qsoln = -(Ccal + msoln ssoln)(T)

              = -[42.2 J/C + (1.50 g + 75 g)(4.184 J/gC)](0.93C)

              = -336.92 J

C. the reaction is exothermic because qrxn is negative

d. the surroundings gained 336.92 J of heat.

e. enthalphy change = Hsoln = (qrxn)/ mass solute = (336.92 J/ 1.50 g) = 224.61 J/g solute

        to determine enthalphy change on per mole basis, molar mass of the solute is needed.

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