O 1 - Energetics Flashcards

1
Q

What are the factors determining the relative solubility of a solute in aqueous and non-aqueous solvents?

A

Temperature, polarity (i.e. ionic bonds, intermolecular bonds etc.), molecular size

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2
Q

What are hydrated ions?

A

An ion surrounded by water molecules in a spherical-shaped shell

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3
Q

What is enthalpy change of solution?

A

The enthalpy change that occurs when one mole of ionic solid dissolves in water to form one mole of aqueous ions, under standard conditions

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4
Q

What is lattice enthalpy?

A

The enthalpy change when one mole of an ionic compound is formed from its gaseous ions, under standard conditions
(exothermic)

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5
Q

What is the enthalpy change of hydration of ions?

A

The enthalpy change when one mole of gaseous ions are completely hydrated by water to form one moles of aqueous ions, under standard conditions

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6
Q

What is charge density?

A

The charge per unit volume/surface area/length

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7
Q

How are lattice enthalpy and enthalpy change of hydration affected by charge density of the ions?

A

The greater the charge density of the ions:
- The more exothermic the lattice enthalpy due to increased electrostatic attraction
- The more exothermic the hydration enthalpy due to increased attraction of water molecules

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8
Q

What is entropy?

A

It measures the number of ways that molecules can be arranged; quite simply it is the measure of disorder in a system

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9
Q

How can you predict whether entropy change is positive or negative?

A
  • Entropy increases from a solid to a liquid/aqueous to a gas. E.g. if a reaction causes a liquid and a solid to form a gas, then the entropy change is positive
  • If there are more gaseous prod7ucts that reactants then entropy will increase and hence the change will be positive
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10
Q

What is the total entropy change equal to?

A

^(total)S = ^(sys)S + ^(surr)S
(total entropy change = entropy change of the system + entropy change of the surroundings)

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11
Q

What is the entropy change of the surroundings equal to?

A

^(surr)S = (-^H) / (T)
where ^H is the enthalpy change of the reaction and T is the temperature in Kelvin

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12
Q

When is a reaction feasible?

A

When the told entropy change, ^(tot)S is positive

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13
Q

How do you calculate the entropy change of the system (given the entropies of reactants and products)?

A

^(sys)S = ^S(products) - ^S(reactants)

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14
Q

What is solubility product?

A
  • The solubility product constant, Ksp, is an equilibrium constant for a solid dissolving in (aqueous) solution
  • The higher its Ksp, the more soluble a substance is hence the more solute that dissolves
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15
Q

How do you calculate Ksp?

A

For reaction: aA(s) <=> cC(aq) + dD(aq)
Ksp = [C]^c[D]^d
Solids are not included as their concentrations don’t affect the expression and are hence insignificant

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