CHEM 101L- EXP. 6 QUESTIONS AND ANSWERS
Experiment 6
In this lab, the temperature of three different reactions will be recorded and graphed.
The graph will be used to extrapolate the maximum temperature of those reactions ,
and those temperatures will in turn be used to calculate their enthalpy change. Enthalpy
is the total heat content of a system. Negative enthalpy changes indicate an exothermic
reaction, as the heat content of the system escapes to its surroundings. Positive
enthalpy changes indicate an endothermic reaction, as the heat content of a system
increases due to the absorption of heat from its surroundings.
enthalpy
- Change in heat between reactants and products
-State function= independent of path
standard enthalpy change (ΔH)
Standard enthalpy changes refer to reactions done under standard conditions, and with
everything present in their standard states.
Standard conditions are:
-298 K (25°C)
-a pressure of 1 atm
Standard heat of formation
the change in enthalpy when one mole of a substance is formed from its pure
elements under standard conditions.
endothermic
- Products are at a lower energy than reactants
- Absorbs heat
exothermic
- Products are at a higher energy than reactants
- Releases Heat
Thermochemistry
study of heat energy involved in chemical reactions and changes of physical state
system
The system is the part of the universe being studied, while the surroundings are the rest
of the universe that interacts with the system.
work
a force that is applied to an object that moves the object
Hess's Law.
If a reaction can be written as the sum of two or more other reactions, the change in
heat for the overall process must be the sum of the change in H values of the constitute
reactions.
How can the enthalpy change of a reaction be predicted by using known data
from 2 or more different reactions - theoretically and experimentally?
You can compare it with the literature data or measure the heat lost and subtract the
sum of products- sum of reactants= change in heat.
Which equipment in this experiment required calibration?
The calorimeter
Experiment 6
In this lab, the temperature of three different reactions will be recorded and graphed.
The graph will be used to extrapolate the maximum temperature of those reactions ,
and those temperatures will in turn be used to calculate their enthalpy change. Enthalpy
is the total heat content of a system. Negative enthalpy changes indicate an exothermic
reaction, as the heat content of the system escapes to its surroundings. Positive
enthalpy changes indicate an endothermic reaction, as the heat content of a system
increases due to the absorption of heat from its surroundings.
enthalpy
- Change in heat between reactants and products
-State function= independent of path
standard enthalpy change (ΔH)
Standard enthalpy changes refer to reactions done under standard conditions, and with
everything present in their standard states.
Standard conditions are:
-298 K (25°C)
-a pressure of 1 atm
Standard heat of formation
the change in enthalpy when one mole of a substance is formed from its pure
elements under standard conditions.
endothermic
- Products are at a lower energy than reactants
- Absorbs heat
exothermic
- Products are at a higher energy than reactants
- Releases Heat
Thermochemistry
study of heat energy involved in chemical reactions and changes of physical state
system
The system is the part of the universe being studied, while the surroundings are the rest
of the universe that interacts with the system.
work
a force that is applied to an object that moves the object
Hess's Law.
If a reaction can be written as the sum of two or more other reactions, the change in
heat for the overall process must be the sum of the change in H values of the constitute
reactions.
How can the enthalpy change of a reaction be predicted by using known data
from 2 or more different reactions - theoretically and experimentally?
You can compare it with the literature data or measure the heat lost and subtract the
sum of products- sum of reactants= change in heat.
Which equipment in this experiment required calibration?
The calorimeter
