Use the References to access important values if weeded for this question. When

Question

Use the References to access important values if weeded for this question. When a solid dassolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee cup Thermometer In the laboratory a general chemistry student finds that when 0.83 g of KOH(s) are dissolved in 112.20 g of water, the temperature of the solution increases from 25.54 to 27.40 C Cardboard or Stymofoam lid The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.84 Nested Styrofoam cup Based on the student's observation, calculate the enthalpy of dissolution of KOH(s) in kJ mol Reaction occurs in solution Assume the specific heat of the solution is equal to the specific heat of water kI mol Retry Enire Group 4 more growp atents eining

Explanation / Answer

Using, q = (m) (Cp)t

Where, (t) = temperature change
Cp =specific heat of water
m = mass of the water

Putting the respective values, we get

q=(112.20 g) x 4.18 j/ g °C x (27.40 - 25.54)°C

q= 872.33 J lost by the water

Supposing the calorimeter to be at the same temperatures as the water:
(1.84 J/°C) x (27.40- 25.54)°C = 3.42 J lost by the calorimeter

872.33J + 3.42 J = 875.75 J total heat lost by the combined apparatus, and gained by the solute

So, enthalpy of dissolution =

(0.87575 kJ /0.83g) * (56.105 g mol-1 KOH)

=59.19 kJmol-1

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