Experiment 2: Introduction to Calorimetry Flashcards
calorimeter defintion
-a calorimeter is the device used for measuring the change in temperature and a chemical or physical process occurs in isolation
-no heat enters or leaves which allows the heat flow of the process to be measured by determining the change in temperature
- a calorimeter only requires an insulated reaction container, a means of mixing the reaction components and a device for measuring the temperature within this isolated system
define calorimetry
- all chemical reactions involve the transfer of energy, if energy is transferred as heat, the change in temperature may be measured and used to learn about the reactions and materials involved
- the science of measuring heat changes that occur in chemical or physical processes is called calorimetry
what type of calorimeter is used in this experiment?
- used an expanded polystyrene calorimeter which is not a sealed system so the internal pressure is equal to the atmospheric pressure
- so the initial pressure of the reactants equals the final pressure of the system after the reaction; so the q (heat of reaction) equals the enthalpy change (△H)
how to find heat, q
-the specific heat of a substance (s) is the heat necessary to raise the temperature of one gram of a substance by one degree
- to find heat, q, required to raise the temperature of a sample, multiply the specific heat, s, by the mass, m, in grams, and the change in temperature
equations to calculate q, delta h, etc.
△H = q = m s △T
or
△H = q = C△T
What is the specific heat, s, of a substance?
The heat necessary to raise the temperature of one gram of a substance by one degree.
What is the total heat capacity, C, of an object?
specific heat x mass
s x m
The law of conservation of energy tells us energy remains constant. What does this mean for calorimetric studies?
Energy lost/gained in reaction must equal energy gained/lost by surroundings. The surroundings include any part of the calorimeter and system that is not part of the reaction. (Excess water, calorimeter itself, the thermometer)
qreaction + qsurroundings = 0
Why is the heat capacity of the calorimeter determined? What is it?
Since there will be a loss or gain of heat from calorimeter, its heat capacity must be known for precise measurements. The heat capacity of the calorimeter is the amount of heat required to raise the temperature of the calorimeter itself by 1 degree.
How can the heat capacity of the calorimeter be determined experimentally? - aka calorimeter constant
Adding known mass of hot water to known mass of cold water in the calorimeter. Heat is lost by the hot water and gained by both cold water and calorimeter, thus:
qhot water = -(qcold water + qcalorimeter)
qcalorimeter = -qhot water - qcold water
Ccalorimeter ΔT = -(msΔT)hot water - (msΔT)cold water
what is enthalpy
the measurement of energy in a thermodynamic system
heat of neutralization is calculated using
Q = mc△T
How can the specific heat of a metal be determined?
Heating sample of metal to known temperature, then placing it into calorimeter, containing a known amount of cool water. Resulting solution is mixed and temperature recorded. Heat lost by metal = heat gained by water because water and metal will reach the same temperature.
specific heat (water) x mass (water) x ΔTwater = specific heat (metal) x mass (metal) x ΔTmetal
Which of the following items are part of the “calorimeter assembly”?
The calorimeter body
The magnetic stir bar
The calorimeter lid
The calorimeter liner
Which balance is used to weigh the calorimeter assembly?
A top-loading balance
