Inorganic chemistry

What is needed for a collision to be successful

Correct orientation and particles must have activation energy

Activation energy definition

The minimum energy required for a reaction to take place

How does rate of reaction change during a reaction

Starts at its quickest, and the rate gradually slows down

What factors can alter rate of reaction

Concentration/pressure

Temperate

Catalyst

Surface area

How does conc/pressure effect ror

Particles are closer together so particle collisions are more frequent collisions so more effective collisions

How to measure ror experimentally (2 ways)

Measuring the decrease in mass using a balance during a reaction or measuring the volume of gas produced

Catalyst definition

When a substance isn’t used up in a reaction and decreases the activation energy

Homogeneous catalyst

Catalyst thats in the same physical state as the reactants

Heterogeneous catalyst

Catalyst thats a different physical state as the reactants (usually solids with gaseous reactants)

How do catalysts work

Reactants are adsorbed onto the surface of the catalyst, where the reaction happens, then the products are desorbed

Benefits of using a catalyst

Lower cost than increasing temp/pressure

Reduces energy needed without being used up

Less CO2 produced as less energy needed

What does the boltzmann distribution look like

How does boltzmann distribution change with temperature

T2 = higher temp

What does the area under the boltzmann distribution represent

The number of molecules

How does a catalyst affect the boltzmann distribution

What makes a system in dynamic equilibrium

When the products are being made at the same rate as reactants are being made in a closed system and the concentrations do not change

What is le Chatelier’s principle

The equilibrium will move to minimise an external change

How does changing concentration affect equilibrium

An increase to one of the sides will shift the equilibrium to the opposite side, and a decrease to one of the sides will shift the equilibrium to that side

How does changing temperature affect equilibrium

Decreasing temperature will shift the equilibrium in the exothermic direction, increasing temperature will shift the equilibrium in the endothermic direction

How does changing pressure affect equilibrium

If pressure is increased, the equilibrium will shift to the direction with less gaseous moles and if pressure is decreased, the equilibrium will shift to the direction with more gaseous moles

Equation for Kc

What does the value of Kc tell us about the equilibrium

Greater than 1: Shifted to the right (products)

1: in the middle

Less than 1: shifted to the left (reactants)

Benefits of a homogeneous catalyst

Increases reaction rate more than hetero because its mixed in with the reactants

Benefits of a heterogeneous catalyst

Easier to remove the catalyst from the reaction mixture

How does surface area affect the rate of reaction

Increasing the surface area will increase the number of molecules that can collide which will increase the frequency of collisions, hence frequency of successful collisions

Electronegativity definition

The ability for atoms to attract the bonding electrons in a covalent bonds

What is the Pauling scale

The measure of electronegativity

What does electronegativity difference dictate

Bond type

How do simple molecular substances interact in polar solvents

Does not dissolves in water

How to represent a hydrogen bond on a diagram

Dashed line between H nucleus and lone pair

What can increase london forces?

The number of electrons in the molecule

If all of the atoms are in a longer and thin structure

Order of intermolecular forces in strength

London forces < permanent dipole dipole < hydrogen bonding

Are non polar substances soluble in polar solvents

No

Is a non polar substance soluble in a non polar solvent

Yes (e.g. hexane)

Why is the solubility of polar molecules are hard to predict?

Depends on the strength of the dipole

How do london forces come about?

Random movement of electrons produces a changing dipole which will induce a dipole on the neighbouring molecules. London forces are the attraction due to these instantaneous dipole.

How do permanent dipole dipole forces arise?

In a polar molecule, the permanent dipoles attract each other so the molecules form an arrangement with positive and negative charges adjacent

What are the anomalous properties of water due to hydrogen bonds

Higher B.P./M.P, high viscosity and surface tension, liquid water is more dense than ice

Why is water less dense than ice

The hydrogen bonds form a open lattice structure which is less dense than liquid structure

What elements form hydrogen bonds

H/N/O/F

Hydrogen bond definition

A strong dipole dipole interaction between a positive hydrogen nucleus and a lone pair of electrons

Symbol for dipoles

What is a polar molecule

A non symmetrical molecule with polar bonds so there is an overall dipole

Factors that affect electronegativity

Nuclear charge, atomic radius and shielding

How many hydrogen bonds does a water molecules form

2 hydrogen bonds

Why are non polar substances insoluble in polar solvents

The intermolecular forces are weaker in the substance so there will not be enough interaction between solvent and solute to dissolve

Why is a non polar substance soluble in a non polar solvent

Because the intermolecular forces interact and weaken in the simple molecular lattice, causing the solvent to move apart and allow the substance to dissolve

How does nuclear charge affect electronegativity

The more protons the stronger the attraction between the nucleus and the bonding pair

How does atomic radius affect electronegativity

Closer to the nucleus means stronger attraction between the nucleus and bonding pair

How does shielding affect electronegativity

Less shells of electrons between the nexulus and shared pair causes stronger attraction

Defintion of a bronsted lowry base

proton acceptor

Definition of a bronsted lowry acid

proton donor

How can H₂O act like an acid and a base

It can accept a proton to form a hydronium ion, and donate a proton to become a hydroxide ion

What type of acid is ethanoic acid (2 words)

weak monobasic

What type of acid is sulfuric acid

Strong dibasic acid

What does “p” mean in chemistry generally

-log of the quantity

Calculating pH for strong acids 

The acids fully dissociate, meaning [acid] = n[H⁺] where n is the number of hydrogens that the acid can donate

pH = ?

-log[H⁺]

General form for Ka (acid dissociation constant) and units

What is pK_a relationship to K_a

pK_a = -logK_a

How do K_a and pK_a vary depending on the strength of the acid

As acid strength increases, K_a increases and pK_a decreases

Expression for K_a of a weak acid (without approximations)

E

Expression for K_a for a weak acid with approximations 

Approximations for calculation pH of a weak acid

That the concentration of hydrogen ions are equal to the concentration of anions (there are some H+ from the water)

We assume the concentration of the acid at equilibrium is equal to the concentration of the acid at the start, as not a lot dissociates

K_w expression and value at 298K

10^-14 

How to calculate pH of a strong base

K_w/[OH-] = [H+] and n[OH-]→[base]

What is a buffer system

Reduces the effect of acids and bases on the system

What components make up a buffer solution

HA and A-

Ways to prepare buffer solutions

Using a salt and acid or partial neutralisation (excess of weak acid with a strong base)

What happens when H+ is added to a buffer solution

H+ ions react with conjugate base, the equilibrium shifts toward the acid which reduces the H+ ions

What happens when OH- is added to a buffer solution

OH- + H+ → H20, so equilibrium shifts toward the H+ + A- as HA dissociates

When [HA] = [A-]

pH = pKa

What is the healthy pH of blood, and the bounds in which pH is safe

7.4, 7.35-7.45

What is the buffer system in the blood

Carbonic acid

How to use a pH meter

You must calibrate the pH meter by dipping in a solution of known concentration of acid/alkali and a neutral solution, depending if we are using an excess of acid/alkali

What is the equivalence point of a titration

The centre of the vertical section of a pH curve, which is wherethe volume of one solution exactly reacts with the volume of the other solution

The colour of an end point to a titration

A colour inbetween the colour of the the conjugate base and weak acid

An indicator is a weak acid, which way is the equilibrium shifted toward when in excess of acid

To the left

At the end point, pKa =

pH

Over what range to indicators change colourq

2 pH

To choose a suitable indicator, what must the pH where it changes colour relate to in the titration

Should encompass the range where the vertical section of a titration is

Graph of strong acid - strong base titration

Graph of weak acid - strong base titration

Graph of strong acid - weak base titration

Graph of weak acid - weak base titration

Lattice enthalpy definition

The enthalpy change that accompanies the formation of 1 mol of an ionic lattice from its gaseous ions under standard conditions

Is lattice enthalpy exo or endo and why

Lattice enthalpy is exothermic because strong electrostatic forces are formed between the oppositely charged ions to achieve a more stable state

Standard enthalpy change of formation definition

The enthalpy change that accompanies the formation of 1 mol of a substance from its constituent elements in their standard states under standard conditions

What is standard enthalpy of atomisation

The enthalpy change when changing an element into a monoatomic gas

Is enthalpy change of atomisation endo or exo

Endothermic because energy is required to break bonds to form a gas

First ionisation energy definition

The minimum energy required to remove 1 electron from each atom is 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions

Is ionisation endo or exo

Endothermic because energy is required to overcome the electrostatic forces between the positive nucleus and the negative electron

What is an electron affinity

When an electron is added to an atom/ion

Is the first electron affinity exo or endo

First electron affinity is exothermic as the negative electron is attracted to a positive nucleus

Is second electron affinity endo or exo

Endothermic because energy is required to force an electron toward a negatively charged ion

Standard enthalpy change of solution definition

The enthalpy change accompanying 1 mole of a solute being completely dissolved in a solute Iunder standard conditions

Is enthalpy change of solution endo or exo

Can be either depending on the relative magnitudes of the enthalpy change of hydration and lattice enthalpy

How to draw a dissolved ion

How to find enthalpy change of solution experimentally

Put a thermometer in a polystyrene cup with water and add the ionic solid, use the mass of the solution and c of water in q=mcT to find enthalpy