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IB Chemistry > Energetics > Flashcards

Energetics Flashcards

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1
Q

What is the difference between and open and closed system?

A

An open system can exchange energy and matter with the surroundings. A closed system can exchange energy but not matter with the surroundings.

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2
Q

What is temperature?

A

Temperature is the average kinetic energy of molecules (K, kelvins)

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3
Q

What is heat?

A

Heat is the amount of energy exchanged due to a temperature difference between two substances (J, joules)

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4
Q

What is enthalpy

A

Enthalpy is the amount of energy or heat content of a substance. The energy is stored in chemical bonds. It incudes kinetic and potential energy and is not measured directly but changers are measured (J)

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5
Q

What is standard enthalpy change of reaction?

A

The difference between the enthalpy of the products and of the reactants at 298K and 1.00 x 10^5Pa

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6
Q

What is change in enthalpy? (Formula)

A

Enthalpy of products - enthalpy of reactants

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7
Q

What value of enthalpy do the most un-stable substance?

A

The higher the value of enthalpy, the less stable the substance

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8
Q

What are examples of exothermic reaction?

A

-Combustion reactions
-Neutralization reactions

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9
Q

Heat energy change (Q)

A

Q (J) = mass (g) x specific heat capacity(J g–1 K–1) x change in temp (K)

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10
Q

What are the standard conditions
for enthalpy changes

A

-100kPa
-1 mol/dm3 for all solutions
-all substances in there standard states

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11
Q

What is the standard state of a substance

A

The standard state of a substance is the pure form of the substance under standard conditions of 298 K (25 °C) and 1.00 × 10^5 Pa

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12
Q

What is the specific heat capacity of water?

A

4.18 J g–1 K–1

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13
Q

What is the standard enthalpy change of combustion?

A

The standard enthalpy change of combustion is the enthalpy change for the complete combustion of one mole of a substance in its standard state in excess oxygen under standard conditions

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14
Q

What are the 4 assumptions we need to make when calculating enthalpy?

A

1 no heat loss from the system
2 all the heat goes from the reaction to the water
3 the solution is dilute: V(CuSO4) = V(H2O)
4 water has a density of 1.00 g cm–

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15
Q

What is Hess’s law?

A

The enthalpy change for any chemical reaction is independent of the route, provided the starting conditions and final conditions, and reactants and products, are the same.

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16
Q

What is standard enthalpy
of formation?

A

The standard enthalpy of formation of a substance is the enthalpy change that occurs when one mole of the substance is formed from its elements in their standard states under standard conditions of 298 K (25 °C) and 1.00 ×10^5 Pa

17
Q

∆H reaction

A

∆H reaction =∑∆H⊖f (products) – ∑∆H⊖f (reactants

18
Q

What is average bond enthalpy?

A

The average bond enthalpy is the energy needed to break one mole of bonds in gaseous molecules under standard conditions averaged over similar compounds.

19
Q

What is ionization energy?

A

The ionization energy is the minimum energy required to remove one mole of electrons from one mole of gaseous atoms.

20
Q

What is electron affinity?

A

Electron affinity is the enthalpy change when one mole of gaseous electrons is added to one mole of gaseous atoms

21
Q

What is lattice enthalpy?

A

The lattice enthalpy is the enthalpy change that occurs when one mole of a solid ionic compound is separated into gaseous ions under standard conditions.

22
Q

What is enthalpy change
of atomization ?

A

The enthalpy change of atomization is the enthalpy change that occurs when one mole of gaseous atoms is formed from the element in its standard state

23
Q

Heat capacity

A

The heat capacity (C) is defined as the heat needed to increase the Temperature of an object by 1 K

24
Q

Specific heat capacity

A

The specific heat capacity (c) is defined as the heat needed to increase the temperature of unit mass of material by 1 K

25
Q

How much heat is released when 10.0 g of copper with a specifc heat capacity of
0.385 J g–1 °C–1 is cooled from 85.0 °C to 25.0 °C

A

heat change = m × c × ∆T
= 10.0 g × 0.385 J g–1 °C–1 × –60.0 °C (the value is negative as
the Cu has lost heat)
= –231 (J)

26
Q

Why is bond breaking Endothermic?

A

A covalent bond is due to the electrostatic attraction between the shared pair of electrons and the positive nuclei of the bonded atoms. Energy is needed to
separate the atoms in a bond.

27
Q

What is Enthalpy of Solution

A

The enthalpy change when one mole of a solute is dissolved in a solvent to infinite dilution under standard conditions

∆Solution = ∆Lattice + ∆Hydration

28
Q

What is Enthalpy change of hydration?

A

The Enthalpy change that occurs when one mole of gaseous ions is dissolved to form an infinitely dilute solution of one mole of aquel ions under standard conditions

29
Q

What is a spontaneous reaction?

A

A reaction which occurs without the need to do work. A spontaneous reaction occurs without adding energy)

30
Q

What is Entropy?

A

The available distribution of available energy among the particles

31
Q

Formula for entropy change of a reaction:

A

Entropy of products - Entropy of reactants

32
Q

Entropy of surrounding is proportional to

A

(Negative) Change in enthalpy

33
Q

Entropy if surrounding is inverse proportional to

A

Temperature

34
Q

Formula for entropy of surroundings

A

(-change in enthalpy) / temperature

35
Q

When is a reaction spontaneous

A

When (entropy of system) - (entropy of surrounding) > 0

36
Q

Formula for Gibs free energy

A

Change in entropy of system - (temperature [K] x entropy change of system) <0

37
Q

Under what conditions is a reaction with a positive entropy of system feasible?

A

High temperature

38
Q

Which reactions can occur at low temperature?

A

Combustion

39
Q

How do we calculate ∆H using bond enthalpies?

A

Bonds Broken - Bonds Formed

IB Chemistry (11 decks)

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