An excess of zinc metal is added to 50.0 mL of a 0.100 M AgNO3 solution in a constant-pressure calorimeter like the one pictured in Figure 6.9. As a result of the reaction
the temperature rises from 19.25°C to 22.17°C. If the heat capacity of the calorimeter is 98.6 J/°C, calculate the enthalpy change for the above reaction on a molar basis. Assume that the density and specific heat of the solution are the same as those for water, and ignore the specific heats of the metals.
Interpretation: The change in enthalpy on molar basis has to be calculated.
Concept Introduction:
Specific heat can be defined as quantity of heat required to raise the temperature of
Where
c= Specific heat
The unit of specific heat is
Answer to Problem 6.115QP
The change in standard enthalpy is
Explanation of Solution
Record the given data
Volume and Molarity of Silver Nitrate =
Initial temperature =
Final temperature =
Heat capacity of calorimeter =
To calculate the heat produced
Heat produced by the reaction =
=
Heat produced by the reaction =
To calculate the heat produced on molar basis
Moles of Silver =
On molar basis, heat produced
=
Heat produced =
To calculate the enthalpy of the reaction
The equation shows 2 moles of Silver, therefore the heat produced =
Heat is produced by the reaction, then,
The enthalpy change of the reaction was calculated using the values of heat produced by moles of Silver. The heat produced by the reaction was found to be
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