Question

When 0.133 g of CaCl2 is dissolved in 100.g of water the temperature of the solution...

When 0.133 g of CaCl2 is dissolved in 100.g of water the temperature of the solution increases by 5.50 °C. How much heat released (q) upon dissolution? What is the H for this reaction? What is the difference between q and H? (the specific heat of the solution is 4.18 J/g°C)

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Answer #1

Q = m c ∆T
Q = quantity of heat in joules (J)
m = mass of the substance acting as the environment in
grams (100 g)
c = specific heat capacity (4.18 for H2O) in J/(g oC)
∆T = change in temperature = Tfinal - Tinitial in oC (5.50C)

Q = 100 x 4.18 x 5.5

Q = 2299 Joules heat released

The enthalpy change, ΔH, in kJ per mole of a given reactant for the reaction is calculated:

ΔH = heat change/1000 ÷ moles

ΔH = Q/1000 ÷ n

0.133 g of CaCl2 = 0.133 / 110.98 = 0.0011984 Moles

ΔH = 2299 / 1000 ÷ 0.0011984   = 1918 KJoules

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