GAMSAT Physical Chemistry

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What is the phase change for a liquid in an endothermic process?
To gas
What substance has more than one liquid form?
What is the equation m x s x change in temp, used to measure?
The energy required to change the temperature in a phase
How to you calculate the energy needed to make a phase change?
Mass x latent heat
Is a nucleophile electron rich or electron poor? What charge does it have?
Rich, usually has a slightly negative charge
What 3 properties do substances bonded by ion-ion interactions have?
High lattice enthalpies, high melting point, and high boiling point
What molecules is a dipole-dipole interaction between?
Polar molecules
How do London interactions occur?
Through fluctuations in in electronic distributions of neighbouring molecules, that tend to align forming transient forces through instantaneous dipoles
Which three strongly electronegative molecules must hydrogen be attached to in order to form hydrogen bonds?
Nitrogen, oxygen or fluoride
Do short chain alkanes have increased or decreased melting point in comparison to long chain alkanes?
Which molecule is dominate when carbon is double bonded to oxygen?
What is the vapour pressure of a liquid defined as?
The pressure exerted by the vapour when the vapour and liquid are in dynamic equilibrium
Why does most evaporation take place near the surface of a liquid?
The intermolecular forces there are less
What is the enthalpy of vaporisation?
The extra energy required by all molecules to change phase as higher energy molecules boil first.
In a Maxwellian energy distribution curve, is the peak of lower temperatures higher or lower than higher temperatures?
What is the triple point in a phase diagram?
The point at which solid, liquid and gas coexist
What is the critical temperature and pressure of a substance?
-Temp: Temperature above which it cannot exist as a liquid
-Pressure: At the critical temp, the minimum pressure at which liquefaction takes place
What changes in temperature and pressure cause a liquid to solidify?
Increased pressure and decreased temperature
Why does the solid-liquid equilibrium boundary in water have a negative slope?
Because in water, the solid form is less dense than the liquid
What happens to the melting and boiling points of most substances if you increase the pressure on them?
They increase
What is the triple point of CO2?
5.2 atm and -57 degrees
What process changes solid carbon dioxide into carbon dioxide gas?
What is the difference between molality and molarity?
Molality is the measure of concentration independent of temperature, where molarity is volume dependent and therefore temperature dependent
When is a solution said to be saturated?
When as much solution dissolves as can at that temperature and pressure
Define Henry’s Law
At a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid
What is the inverse of Henry’s constant?
The molar solubility at 1 atmosphere of partial pressure
What are the 4 colligative properties of solvents?
1) Lowering of vapour pressure of the solvent
2) Elevation of the BP of the solvent
3) Depression of the MP of the solvent
4) Osmosis
Define Raoult’s Law
The vapour pressure of a solvent in a solution of a non-volatile solute is directly proportional to the mole fraction of the solvent in solution
What equation is used in Raoult’s law?
P (vapour pressure) = Mole fraction of the solvent x P’ (vapour pressure of the pure solvent)
How do you calculate osmotic pressure?
Van’t Hoff factor x gas constant x temperature (K) x molarity
How can a mixture of liquids, with different boiling points, be separated?
What is the Tyndall effect?
The scattering of light by colloidal particles
Define rate of reaction
The change in concentration of a reactant or product per unit of time
How do you calculate rate of reaction?
Rate = k.[A]a.[B]b.[C]c…
Does a first order reaction or second order reaction depend on half-life?
Second order
What is activation energy?
The energy needed to start a reaction (minimum energy required by the particles to react)
Categories: Physical Chemistry