Solution.
Assume that the heat capacity of salt solutions is equal to the heat capacity of water. Now let's find a substance in excess (the limiting reagent):
"n(MCl2) = 0.1929 \\times 1 = 0.1929 \\ mol"
"n(K2SO4) = 0.1929 \\times 0.5 = 0.0965 \\ mol"
K2SO4 is limiting reagent.
According to the reaction equation, the amount of substance sulfate ions is equal to the amount of substance insoluble compound, so n(K2SO4) = n (MSO4).
According to the condition of the problem, the water (solutions) and the calorimeter were in equilibrium, then:
"Q(cal) = Q(H2O)"
"Q(cal) = C(cal) * \\Delta t"
"Q(cal) = 1.75 \\times 10^3 \\times (29.6-24.5) = 8.925 \\times 10^3 \\ J"
The amount of heat is equal to the enthalpy of the reaction taken with the inverse sign, so:
"\\Delta H = -Q"
"\\Delta H(mole) = \\frac{-Q}{n(MSO4)}"
"\\Delta H(mole) = \\frac{-8.925 \\times 10^3}{0.0965} = -92.49 \\ \\frac{kJ}{mol}"
Answer:
"\\Delta H(mole) = -92.49 \\ \\frac{kJ}{mol}"
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