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100 mL of a 0.300 M solution of AgNO3 reacts with 100 mL of a 0.300 M solution of HCl in a
coffee-cup calorimeter and the temperature rises from 21.80 °C to 23.20 °C. Assuming the density
and specific heat of the resulting solution is 1.00 g/mL and 4.18 J/g. °C, respectfully, what is the
AHºx?
A 39.0 kJ/mol
B +39.0 kJ/mol
C.+1.17 kJ/mol

Answer :

Sebassandingo

Answer:

[tex]\Delta _rH=-39,1kJ[/tex]

Explanation:

Hello!

In this case, since it is possible to assume that the heat released by the reaction is absorbed by the water in the calorimeter we can write:

[tex]Q_{rxn}=-200mL*\frac{1g}{1mL}*4.184\frac{J}{g\°C}*(23.20\°C-21.80\°C)\\\\Q_{rxn}=-1,171.5J[/tex]

Now, since the reaction between silver nitrate and hydrochloric acid is:

[tex]HCl+AgNO_3\rightarrow AgCl+HNO_3[/tex]

We can see there is a reacting 1:1 mole ratio, thus, the reacting moles are computed via the molarity of the solutions:

[tex]n=0.300mol/L*0.100L=0.0300mol[/tex]

Finally, the enthalpy of reaction is:

[tex]\Delta _rH=\frac{-1,171.5J}{0.0300mol}=-39,050.7J[/tex]

And in kJ:

[tex]\Delta _rH=-39,1kJ[/tex]

Best regards!

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