Question

Pre-Lab Questions: Thermochemistry MUST be completed before an experiment is started. Show all work and be sure to include units. Q What is the difference between heat capacity and specifie heat? What are the units for each? Q2. What is a calorimeter, and why is it used in thermochemistry? Why should you measure the specific h the calorimeter? Q3. What is the sign +or-) of the temperature change for a piece of hot metal when it is placed in cold w Explain 04. What equation will be used to determine the specific heat of the metal? Q5. When calculating the heat of reaction, do you use only the mass of the solvent, water? Explain.

Answer 1

1) Difference between heat capacity and specific heat capacity is that heat capacity is the amount of heat required to raise the temperature of a substance by one degree celsius. It is extensive property.

Units : J/^OC or J/K

Specific heat capacity is the amount of heat required to raise the temperature of a unit mass by one degree celsius. It is intensive property.

Units : J/gm ^OC or J/gm K

2) Calorimeter : It is a device which is used to measure the amount of heat involved in a chemical or physical processi.e transfer of heat to or from the substance. Calorimeter is very crucial in thermodynamics as it involves in the measurement of heat of reaction. The specific heat capacity is measured because it shows how different substances absorb and transfer energy to the surroundings/ calorimeter.

3) The sign of a temperature change when a piece of hot metal is placed in a cold water will be negative because the high temperature of hot metal will transfer the heat to water (old water) through conduction and decreases the temperature of metal itself.

4) The equation used to measure specific heat capacity of metal : (c_p) is the ratio of heat gaind by the water and the product of mass of substance and change in temperature.

C_p = heat gained by the water/ mass of substance x $\Delta$ change in temperature.

5) During calculating heat of reaction with surroundings i.e adiabatic calorimeter can be determined by

$\Delta$ H = -m_water S_water $\Delta$ T _calorimeter

mass of water (solvent) is considered because it also contributes to the heat of a reaction.

The heat change associated with a chemical reaction was studied using calorimetric techniques. In a specific reaction the heat raises the temperature of one degree celsius by some amount, it is the same quantity of heat simulataneously raise the temperature of certain mass of water i.e specific heat of water and the mass of water is called as water equivalent.