units calculations energy vocab temperature
TRANSCRIPT
Units
Calculations
Energy
Vocab
Temperature
Grab Bag
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What is the SI unit for
temperature?
Kelvin
What is the unitfor molar heat
capacity?
J/K mol∙
What is the unit for n?
mol
What is the unitof energy? Write
the word and symbol on the board.
Joules, J
What is the unit for molar enthalpy?
J/mol
What is the genericequation for
changing Celsius into Kelvin.
°C + 273= K
Use this equation if you are finding
the change in heat for 25g of
water.
q =nC∆T
Use this equation if you are finding the molar
enthalpy change and do not have the amount in
moles.
∆ H=C∆T
What is the generic equation for finding the change in enthalpy for a
reaction using Enthalpies of Formation?
∆H= ∆H°f products- ∆H°f reactants
Calculate the change in enthalpy when forming
aluminum oxide. 2Al(s) + 3H2O(l)→ Al2O3(s) + 3H2(g)
∆Hf H2O= -285.8 kJ/mol ∆Hf Al2O3= -1676.0 kJ/mol
-1676.0-(3x-285.8)=
-818.6kJ/mol
If the energy change in a reaction
is negative the reaction is
__________.
Exothermic
When ∆H is positive, the reaction is
__________.
Endothermic
What is the only way we
measure energy?
With a thermometer
Calculate the molar enthalpy change of N2(g) when it is
heated from 90.0°C to 100.°C. The molar heat capacity of nitrogen is 29.1 J/K mol. ∙
Don’t forget to round to the correct sig figs.
291 J/mol
Calculate ∆H for this reaction:3Fe2O3(s) → 6Fe(s) + 4.5O2(s)
3Fe2O3(s)→2Fe3O4(s) + 1/2O2(s) ∆H=-316kJ/mol3Fe(s) + 2O2(g) → Fe3O4(s)
∆H=-201kJ/mol.
86kJ/mol
Definemolar heat
capacity. Hint: think about the units
The amount of energy required to raise 1 mole of
a substance 1K.
Defineextensive property.
A property that depends on the
amount of substance, like heat.
Define intensive property.
Is heat or temperature
intensive?
A property that is independent of the
amount of substance, like temperature.
Define heat.
The energy transferred between
two objects of different
temperatures.
Define Hess’s Law.
The change in enthalpy for a reaction is equal to
the sum of the individual enthalpy
changes.
Definetemperature.
The average kinetic energy of the particles in an
object.
Convert 17°C to Kelvin.
17°C + 273= 315K
Correctly write the standard thermodynamic
temperature in Celsius and Kelvin on the board. This is
the temp that the reactants are at for all heat
measurements
25°C and 298K(no degree symbol for K)
What is ∆T in Kelvin if an object is
cooled from 50°C to 30°C.
20K
What is the generic equation when
solving for ∆T in this equation: q=nC∆T?
∆T = q/nC
Write the symbol(s) for “the change in
temperature” on the board.
∆T
How many sig figs does the following measurements have?a. 4500Jb. 350.Jc. 111.0J
a. 4500J= 2b. 350.J = 3c. 111.0J = 4
What do all the variables in q=nC∆T
represent?
q= heatn= molesC= molar heat capacity∆T = temperature
This chapter is about Thermodynamics, it is the study of _______
changes.
energy
Explain why a balloon with 50mL of water in it won’t pop when a flame is held to it.
Because the molar heat capacity of water is high
(which means it takes a lot of energy to heat water). and the
energy from the flame is transferred to the water
before the balloon.
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