23 ignment/takeCovalentActivity do?locator assignment-take Uve the References to

Question

23 ignment/takeCovalentActivity do?locator assignment-take Uve the References to access inpertast valars if seeded lar thi qoesitios When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determised Then using a coffee cup calorimeter in the laboratory a general chemistry student finds that when 6.27 g of KBris) are dissolved in 112.10 g of water, the temperature of the solution drops from 24.01 to 21.56 °C The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.57 J C Based on the student's observation, calculate the enthalpy of dissolution of KBris) in kImol Assume the specific heat of the solution is equal tothe specifi heat or water. kJ/mol Retry Entire Group 4 more group atempts remaining Submit Answer

Explanation / Answer

mass of KBr = 6.27 g

moles of KBr = 6.27 / 119 = 0.0527 mol

mass of solution = 6.27 + 112.10 = 118.37 g

specific heat = 4.18 J / g oC

temperature rise = 24.01 - 21.56 = 2.45 oC

Q = m Cp dT + Cp dT

   = 118.37 x 4.184 x - 2.45 + 1.57 x 2.45

Q = -1217.2 J

delta H = - Q / n

             = 1.217 / 0.0527

delta H = 23.1 kJ/mol

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