Heat Transfer
A Endothermic process absorbs or releases heat?
Absorbs heat.
Enthalpy is represented by what symbol?
ΔH
What is the equation to calculate heat energy?
Q = mc (delta T)
What is the definition of Hess's Law?
The enthalpy change accompanying a chemical reaction is independent of the pathway between the initial and final states.
Sublimation is ________________.
An exothermic Process releases or absorbs heat?
releases heat.
What is the equation to find enthalpy of a reaction?
Delta H = Sum of Delta H (bonds breaking) - Sum of Delta H (bonds forming)
Delta H = Sum of Delta H (reactants) - Sum of Delta H (products)
What does a positive Q value represent?
An endothermic reaction. Heat entering the system.
How do we use bond enthalpies of various bonds to calculate enthalpy of a reaction?
We use the equation...
Delta H reaction = Sum (Delta H of bonds breaking) - Sum (Delta H of bonds forming)
Phase change from gas to liquid.
The Activation Energy is the energy that is required to:
break the bonds in the reactants.
What is the equation to find enthalpy of formation?
An exothermic reaction releases energy(heat), so its Q will be: A) (+) or B) ( - ) or C) zero
B. (-) Negative
Complete Example #1 - calculating the enthalpy for the reaction on the paper.
+226.7 kJ
Deposition is ______________.
Phase change from gas to solid with no liquid phase.
When there is no heat transfer between two objects. (Both objects are at the same temperature)
What is Entropy and what is its symbol?
Entropy is the measure of how the available energy is distributed among the particles (disorder of a system).
Heat transfers from ____ to ____ objects.
Hot, Cold
-1075 kJ
Evaporation (vaporization) is ________________.
Phase change from liquid to gas.
What is the difference between temperature and heat?
Temperature is a measure of the average kinetic energy of particles.
Heat is a form of energy that flows from something at a higher temperature to something at a lower temperature.
ΔS can be calculated how?
Delta S = Sum(Delta S of products) = Sum(Delta S of reactants)
When 1.20 grams of C6H14 are burnt, the temperature of 250 grams of water is raised by 56 degrees Celsius. Calculate the enthalpy change (Q) when one mole of C6H14 is burnt.
-4200 kJ/mol
Calculate the enthalpy change (Delta H) for the reaction on the paper.
-2831 kJ
If a substance undergoes a phase change, its composition also changes. (True or False or Sometimes?)
False