west OWLY2 1 Online teac Use the References to eccess When a solid dissolves in
ID: 1045026 • Letter: W
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west OWLY2 1 Online teac Use the References to eccess When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee cup calorimeter In the laboratory a general chemistry student finds that when 3.72 g of NH,CIO() are dissolved in 108.00g of water, the temperature of the solution drops from 24.56 to 22.03 °C The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.72 JC Based on the student's observation, calculate the enthalpy of dissolution of NH,CIO,(s) in kJ/mol. Assume the specific heat of the solution is equal to the specific heat of water. kJ/mol Submit Answer Retry Entire Group 9 more group attempts remainingExplanation / Answer
enthalpy of dissolution of NH4ClO4
Q (heat of solution) = mC(T2-T1) and will be always negetive
where, m = total mass of components,c is the heat capacity and (T2-T1) is the temperature drop.
m = 108 + 3.72 = 111.72g ; (T2-T1) = -2.53
putting values,Q = 111.72*1.72*-2.53 = 469.97 Joules (J)
and enthalpy of dissolution is the heat per mole
no.of moles of NH4ClO4 = weight/ molecular weight = 3.72/117.49 = 0.032 moles
Enthalpy of dissolution (del H) = 469.97/0.032 =14686 joules per mole = 14.686 KJ/mol.
enthalpy of dissolution of CsBr
Similarly as solved for above part,
Q = 130.52*1.64*-2.95 = -631.45 joule
Enthalpy of dissolution = Q/ no. of moles
no of moles = 10.62/212.81 = 0.05 moles
which is equal to -631.45/0.05 = 12620 jolues per mol = 12.62 KJ/mol
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