Units

Calculations

Energy

Vocab

Temperature

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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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