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An 8.5 g. Of ethanol (C2H5OH) placed in a constant volume calorimeter and the temperature rose to 3.2°C. Find the heat of reaction of the ethanol (MM =46.1 g/mol) in kJ/mol. The heat capacity of the calorimeter plus water is read as 6.38 J/°C

Sagot :

sebassandin

Answer:

[tex]\Delta H_{rxn}=-0.111 \frac{kJ}{mol}[/tex]

Explanation:

Hello!

In this case, since the total heat flow due to the reaction equals the negative of the calorimeter's heat, we can first compute the former as shown below:

[tex]Q_{rxn}=-C\Delta T\\\\Q_{rxn}=6.38\frac{J}{\°C}*3.2\°C=-20.416J[/tex]

Now, since this total heat flow due to the reaction is defined in terms of the heat of reaction and the total reacted moles:

[tex]Q_{rxn}=n*\Delta H_{rxn}[/tex]

Thus, we compute the moles in 8.5 g of ethanol:

[tex]n=8.5g*\frac{1mol}{46.08g}=0.185mol[/tex]

Therefore, the heat of reaction results:

[tex]\Delta H_{rxn}=\frac{Q_{rxn}}{n} =\frac{-20.416J}{0.185mol} =-110.7J/mol\\\\\Delta H_{rxn}=-0.111 \frac{kJ}{mol}[/tex]

Best regards!

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