A chemical reaction is carried out in a calorimeter with the following heat capacity (C = 263.8 J/ºC).  The reaction occurs in 27.4 g of water.  The initial temperature before the reaction is 23.1 ºC and the final temperature after the reaction is 69.5 ºC.  The temperature change is the same for the water as it is for the calorimeter.  What is the energy change for the reaction (qrxn) in kJ?

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A chemical reaction is carried out in a calorimeter with the following heat capacity (C = 263.8 J/ºC).  The reaction occurs in 27.4 g of water.  The initial temperature before the reaction is 23.1 ºC and the final temperature after the reaction is 69.5 ºC.  The temperature change is the same for the water as it is for the calorimeter.  What is the energy change for the reaction (qrxn) in kJ

 

The qwater can be found using q=mCs∆T. 

 

The qcalorimeter can be found using q=C∆T. 

In this case, there are 3 energy changes that are happening (qcal, qwater, and qreaction).  The sum of those 3 energy changes will be equal to zero.  Be sure to be careful with the sign of each value

Expert Solution
Step 1 Formula used

Heat exchanged when a substance undergoes a change in temperature T is given by,

q = CT

where C is the heat capacity of the substance.

Also,

q = mCsT

where Cs is the specific heat capacity and m is the mass of the substance.

Due to the law of conservation of energy, the total heat exchange between the system and surroundings is zero.

 

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