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When 15.0 g of a salt was dissolved in 68.8 g of ethyl alcohol, the temperature of the solution decreased from 25.0 °C to 6.0 °C. The specific heat capacity for ethyl alcohol is 2.440 J/g°C. Calculate the heat of reaction (∆H) in units of kJ/g. (Equation 1 and Equation 2 will be helpful.)

Respuesta :

Explanation:

As we know that,

        [tex]H_{rxn} = \frac{-Q}{mass}[/tex]

It is given that, [tex]m_{1}[/tex] = 15 g of salt,   [tex]m_{2}[/tex] = 68.8 g of ethanol

Therefore, total mass is as follows.

    Total mass = [tex]m_{1} + m_{2}[/tex]

                       = (15 + 68.8) g

                       = 83.8  g

Also, change in temperature is as follows.

              dT = [tex](6 - 25)^{o}C[/tex]

                    = [tex]-19^{o}C[/tex]

Now, the relation between heat energy, specific heat and mass is as follows.

               Q = [tex]m \times C_{p} \times (dT)[/tex]

                   = [tex]83.8 g \times 2.440 J/g^{o}C \times (-19)^{o}C[/tex]

                   = -3884.968 J

Therefore, heat of the reaction is as follows.

            [tex]H_{rxn} = \frac{-Q}{mass}[/tex]

                       = [tex]\frac{-3884.968}{15 g}[/tex]

                      = 258.99 J/g

As 1 J = 0.001 kJ. So, heat of reaction in kJ is 0.2589 kJ/g.

Thus, we can conclude that heat of reaction is 0.2589 kJ/g.

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