Energetics Revision Lesson

Energetics
Revision

Defintions

Topic 8 ​Energetics 1

Standard Enthalpy Changes of:
Reaction
Formation
Combustion
Neutralisation

Drag and Drop

The enthalpy change, $$\Delta H$$ , is the heat energy change measured at constant pressure and that standard conditions are​

Placeholder

and a specified temperature, usually ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

100 kPa

298 K

100 Pa

0 K

Drag and Drop

Standard enthalpy change of formation is the enthalpy change measured at standard conditions, when ​

Placeholder

of a substance is formed from its​

Placeholder

in their ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

one mole

elements

standarded states

Drag and Drop

Standard enthalpy change of combustion is the enthalpy change measured at standard conditions when ​

Placeholder

of a substance is ​

Placeholder

burned in ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

one mole

completely

oxygen

incompletely

Drag and Drop

Standard enthalpy change of neutralisation is the enthalpy change measured at standard conditions when ​

Placeholder

of​

Placeholder

is produced by neutralisation of an acid with an alkali.

Drag these tiles and drop them in the correct blank above

one mole

water

Drag and Drop

Standard enthalpy change of atomization is the. enthalpy change measured at standard conditions when ​

Placeholder

of ​

Placeholder

atoms is formed from an ​

Placeholder

in its standard state.

Drag these tiles and drop them in the correct blank above

one mole

gaseous

element

Multiple Choice

For which equation is the enthalpy change correctly described as an enthalpy change of formation?

• 2NO(g) $$\rightarrow$$  N2(g) + O2 (g)

• 2CO(g) + O2(g) $$\rightarrow$$ 2CO2(g)

• H2O(l) + NaCl (s) $$\rightarrow$$ NaCl(aq)

• K(s) + Mn(s) +2O2(g) $$\rightarrow$$  KMnO4(s)

Multiple Choice

Which equation has an. enthalpy change of reaction which corresponds to the standard enthalpy change of atomization of chlorine?

• 1/2 Cl₂(g) $$\rightarrow$$  Cl(g)

• 1/2 Cl₂(l) $$\rightarrow$$  Cl(g)

• Cl₂(g) $$\rightarrow$$  2Cl(g)

• Cl₂(l) $$\rightarrow$$  2Cl(g)

Labelling

Label the following profile for the reaction:

CaCO₃ --> CaO + CO₂

Drag labels to their correct position on the image

Products

CaCO₃

CaO + CO₂

Reactants

ΔH (positive)

Activation Energy

ΔH (negative)

Labelling

Label the following profile for the reaction:

N₂ + 3H₂ --> 2NH₃

Drag labels to their correct position on the image

ΔH (positive)

Reactants

Activation Energy

ΔH (negative)

N₂ + 3H₂

Products

2NH₃

Multiple Select

The equation for a reaction is shown.

H₂(g) + 1/2 O₂(g) → H₂O (l) ; ΔH = x kJ mol ^-1

Tick all that are correct.

• It represents enthalpy change of formation only.

• It represents enthalpy change of formation and combustion.

• x is positive

• x is negative

Multiple Choice

Which of the following processes is endothermic?

• the condensation of steam

• the freezing of water

• the decomposition of calcium carbonate into calcium oxide and carbon dioxide

• the reaction between hydrogen ions and hydroxide ions

Multiple Choice

The enthalpy change for the neutralization reaction below is − 114 kJ mol ^-1.

2NaOH (aq) + H₂SO₄(aq) ----> Na₂SO₄(aq) + 2H₂O(l)

Use this information to suggest the most likely value for the enthalpy change for the following neutralization reaction.

Ba(OH)₂ (aq) + 2HCl(aq) ----> BaCl₂(aq) + 2H₂O(l)

• − 57 kJ mol ^-1

• − 76 kJ mol ^-1

• − 114 kJ mol ^-1

• − 228 kJ mol ^-1

Multiple Choice

The enthalpy change for the neutralization reaction below is − 114 kJ mol ^-1.

2NaOH (aq) + H₂SO₄(aq) ----> Na₂SO₄(aq) + 2H₂O(l)

Use this information to suggest the most likely value for the enthalpy change for the following neutralization reaction.

NaOH (aq) + HCl(aq) ----> NaCl(aq) + H₂O(l)

• − 57 kJ mol ^-1

• − 76 kJ mol ^-1

• − 114 kJ mol ^-1

• − 228 kJ mol ^-1

Hess Cycles

Key Principle

The energy change for a reaction is the same, irrespective of the route taken, assuming the starting conditions are unaltered

Multiple Choice

• -570

• -790

• -860

• -1080

Draw

The enthalpy changes of formation of gaseous ethene and gaseous ethane are +52 kJ mol ^-1and − 85 kJ mol ^-1 respectively at 298 K.

What is the enthalpy change of reaction at 298 K for the following process?

C₂H₄(g) + H₂(g) ---> C₂H₆(g)

Construct a Hess cycle and calculate.

Making an approximation for the enthalpy change of a reaction

​Uses:

The heat energy required to break a mole of gaseous bonds homolytically in the gaseous state.

​Definition

Bond Enthalpies

​Limitations:

-bond enthalpies are averaged for all similar bonds
- energies are all in gaseous state

Drag and Drop

Mean bond enthalpy is the enthalpy change when ​

Placeholder

of a bond in the ​

Placeholder

state, averaged out over many ​

Placeholder

molecules, is ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

one mole

gaseous

different

broken

formed

Multiple Choice

Which one of the following statements about an endothermic reaction is correct?

• The energy absorbed in bond breaking is greater than the energy released in bond forming

• The energy absorbed in bond breaking is less than the energy released in bond forming

• The energy released in bond breaking is greater than the energy absorbed in bond forming

• The energy released in bond breaking is less than the energy absorbed in bond forming

Drag and Drop

Bond enthalpy is the heat ​

Placeholder

required to break a ​

Placeholder

of bonds ​

Placeholder

in the gaseous state.

Drag these tiles and drop them in the correct blank above

energy

mole

homolytically

heterolytically

typcial

entropy

Multiple Choice

• 221.5

• 463.5

• 588

• 927

Multiple Choice

• -95

• -208

• -1080

• -93

Drag and Drop

The enthalpy of formation of Ammonia is given as -46.1kJ/mol, the last answer (-93kJ/mol) is different for several reasons...

1) The energy change is for ​

Placeholder

moles of ammonia forming, the enthalpy of ​

Placeholder

is for ​

Placeholder

mole forming.

2) The bond enthalpies are ​

Placeholder

bond enthalpies and not ​

Placeholder

to ammonia

Drag these tiles and drop them in the correct blank above

two

one

formation

mean

specific

three

hydrogenation

gaseous

vague

Multiple Choice

• 4.9

• 6.5

• 8.7

• 13.0

Multiple Choice

In an experiment, 1.000 g of a hydrocarbon, A, was burned completely in oxygen to produce 3.143 g of carbon dioxide and 1.284 g of water.

In a different experiment, the molar mass of the hydrocarbon, A, was found to be 84.0 g mol^–1.

A spirit burner was filled with the liquid hydrocarbon, A. The burner was weighed, lit and then used to raise the temperature of a quantity of water in a beaker, as shown in the diagram. The burner was then reweighed.

Calculate the Enthalpy of Combustion - to an appropriate number of significant figures

• -2790

• -1860

• -3650

• -8670

Multiple Choice

Using 150ml of water, and 0.717g of methanol the heat transferred to the water was 9860J, calculate the enthalpy of combustion of methanol, include a sign and appropriate number of significant figures

• -205

• -450

• -400

• +320

• +150

Dropdown

The burner lid increases the ​

Select answer

of the experiment by ​

Select answer

the amount of pentane ​

Select answer

.

Lattice Enthalpy

​Defintion

The change in heat energy when one mole of an ionic lattice is formed from its constituent gaseous ions.

e.g. Na⁺_(g) + Cl^-_(g) --> NaCl_(s)

Multiple Choice

Na⁺ (g) + Cl^- (g) --> NaCl (s)

• Ionisation

• Combustion

• Lattice enthalpy

• Atomisation

Multiple Choice

Mg (s) --> Mg (g)

• Ionisation

• Combustion

• Formation

• Atomisation

Multiple Choice

Cl (g) + e- --> Cl- (g)

• Ionisation

• Electron Affinity

• Combustion

• Formation

Multiple Choice

Mg (g) --> Mg+ (g) + e-

• Ionisation

• Combustion

• Formation

• Hydration

Multiple Choice

Na+ (g) + Cl- (g) --> Na+ (aq) + Cl- (aq)

• Formation

• Solution

• Combustion

• Hydration

Multiple Choice

½ H2 (g) + ½ Cl2 (g) --> HCl (g)

• Formation

• Combustion

• Atomisation

• Ionisation

Multiple Choice

O^- (g) + e- --> O^2- (g)

• 1st electron affinity

• 2nd electron affinity

• 3rd electron affinity

• 4th electron affinity

Multiple Choice

C (g)+ O2 (g)--> CO2 (g)

• Ionisation

• Combustion

• hydration

• solution

Multiple Choice

First electron affinity of an element is usually ________ and second electron affinity is ____________.

• exothermic, endothermic.

• exothermic, exothermic.

• endothermic, endothermic.

• endothermic, exothermic.

Multiple Choice

What enthalpy change does the number 4 represent?

• Formation

• 1^st ionisation energy of Na

• 1^st electron affinity of Na

• Atomisation of Na

Multiple Choice

Identify the enthalpy change represented by letter g.

• Enthalpy of formation

• Lattice Enthalpy

• Electron affinity of bromine

• Enthalpy of atomisation of zinc

Multiple Choice

Enthalpy change is represented by step y ?

• Enthalpy of formation calcium bromide

• Enthalpy of atomisation of calcium

• 1^st electron affinity of bromine

• Enthalpy of atomisation of bromine