lecture 4 thermo

Question 1

What is the heat of fusion?

Answer 1

Solid to Liquid. the change in its enthalpy resulting from providing energy, typically heat, to a specific quantity of the substance to change its state from a solid to a liquid

Question 2

What is the heat of vaporisation?

Answer 2

Liquid to Gas. The amount of energy that must be added to a liquid substance, to transform a quantity of that substance into a gas

Question 3

What is the heat of sublimation?

Answer 3

Solid to gas. The heat required to change one mole of a substance from solid state to gaseous state

Question 4

What does Delta H stand for?

Answer 4

Change in enthalpy

Question 5

What is an exothermic reaction?

Answer 5

A chemical reaction that releases energy through light or heat. Bond forming

Question 6

What is an endothermic reaction?

Answer 6

A chemical reaction that absorbs energy. Bond breaking

Question 7

What are extensive properties?

Answer 7

A property that changes when the amount of matter in a sample changes. Examples are mass, volume, length, and charge.

Question 8

What are intensive properties?

Answer 8

A property of matter that depends only on the type of matter in a sample and not on the amount. Other intensive properties include color, temperature, density, and solubility

Question 9

What is hess’s law?

Answer 9

the change of enthalpy in a chemical reaction (i.e. the heat of reaction at constant pressure) is independent of the pathway between the initial and final states.

Question 10

What are standard conditions?

Answer 10

Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data.

Question 11

What is the standard molar enthalpy of formation?

Answer 11

is defined as the change in enthalpy when one mole of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its pure elements under the same conditions

Question 12

What are spontaneous reactions?

Answer 12

A spontaneous process is the time-evolution of a system in which it releases free energy and it moves to a lower, more thermodynamically stable energy state.

Question 13

What are non-spontaneous reactions?

Answer 13

Non-spontaneous reactions require an energy input or a catalyst to lower the energy requirements to take place,i.e. they can only occur if energy is put into the reaction from an external source.

Question 14

What is entropy?

Answer 14

Entropy is defined as the quantitative measure of disorder or randomness in a system

Question 15

What is the second law of thermodynamics?

Answer 15

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy.

Question 16

How can entropy help with drug discovery?

Answer 16

The measure of the heat could indicate whether the drug had interacted with the target.

Question 17

What is delta fH?

Answer 17

The enthalpy change for the formation of 1 mol of a compound directly from its component elements in their standard states.

Question 18

How can you use delta fH to calculate deltaH?

Answer 18

DeltarH = (the sum of all the standard enthalpy of formation changes of the products) - (the sum of all the standard enthalpy changes of the reactants)

Question 19

What are combustion reactions?

Answer 19

CO2 and Water

Question 20

What is dissolution?

Answer 20

In chemistry, to dissolve is to cause a solute to pass into a solution. Dissolving is also called dissolution. Typically, this involves a solid going into a liquid phase, but dissolution can involve other transformations as well.

Question 21

What is crystallisation?

Answer 21

The (natural or artificial) process by which a solid forms, where the atoms or molecules are highly organized into a structure known as a crystal.

Question 22

What is the thermodynamic cycle?

Answer 22

A thermodynamic cycle consists of a linked sequence of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state.

Question 23

The enthalpy of hydration is what?

Answer 23

-ve, strongly exothermic

Question 24

What are the basic things you can use to determine whether a reaction or physical process will occur or not?

Answer 24

Thermodynamics and kinetics

Question 25

What is spontaneity?

Answer 25

the condition of being spontaneous; spontaneous behaviour or action.

Question 26

Are exothermic reactions always spontaneous?

Answer 26

No. for example steam to water is always exothermic but only occurs at a certain temperature

Question 27

Are endothermic reactions alway non-spontaneous?

Answer 27

No. for example ice to water is endothermic but ice melts under normal conditions

Question 28

What is lattice enthalpy?

Answer 28

The enthalpy of formation of one mole of a solid salt from ions in the gas phase. AKA Solid salt to Gas phase

Question 29

What is the enthalpy of hydration defined as?

Answer 29

The enthalpy of transferring ions to water surrounding each ion with water molecules