Chemistry - Level 3 Externals (3.4 and 3.6)

Trigonal bipyramidal

5,5,0 (Symmetrical)

Seesaw

5,4,1 (Unsymmetrical)

T-shaped

5,3,2 (Unsymmetrical)

Linear (5)

5,2,3 (Symmetrical)

Octahedral

6,6,0 (Symmetrical)

Square-based pyramid

6,5,1 (Unsymmetrical)

Square planar

6,4,2 (Symmetrical)

Repulsion statement

These regions repel to the maximum extent possible, giving a base shape of ___

Why are bonds polar?

Due to a difference in electronegativity

General attractive forces statement

The stronger the total IMF's the more heat energy required to overcome them, and so the higher the bp/ ΔvapHo

H-bonding (between molecules)

Occurs when H is bonded to N/O/F within the molecule causing a large dipole due to the large e-neg difference

pda's

___ is polar so has pda's

tda's

The larger the e- cloud, the stronger the tda's. The larger the surface area, the stronger the tda's.

Tetrahedral

4,4,0 (Symmetrical)

Trigonal pyramidal

4,3,1 (Unsymmetrical)

Bent/V-shaped (4)

4,2,2 (Unsymmetrical)

Linear (4)

4,1,3 (Unsymmetrical)

Trigonal planar

3,3,0 (Symmetrical)

Bent/V-shaped (3)

3,2,1 (Unsymmetrical)

Linear (2)

2,2,0 (Symmetrical)

Atomic Radius

The distance between the nucleus and the valence electrons

Electronegativity

The attraction of (the nucleus of) a covalently bonded atom to its bonding electrons

1st Ionisation Energy

The energy required to remove 1 mol of the outermost electrons from 1 mol of gaseous atoms

What factors affect the periodic trends?

The nuclear charge (no. of p+). The no. of e-shells (distance). The no. of inner e-shells (shielding). Which all influence the electrostatic attraction between the nucleus and the relevant electrons.

Shielding (definition)

Repulsions between electron shells

ΔfusHo (standard enthalpy (heat) of fusion)

The energy required to convert 1 mol of solid to 1 mol of liquid at its mp

ΔvapHo (standard enthalpy (heat) of vaporisation)

The energy required to convert 1 mol of liquid to 1 mol of gas at its bp

ΔsubHo (standard enthalpy (heat) of sublimation)

The energy required to convert 1 mol of solid to 1 mol of gas at its sp

Q = m c Δt

Q = heat energy transferred to or from the water m = mass of the water (1mL = 1g) c = specific heat capacity of water Δt = change in temperature of the water

ΔrHo = - Q/n

ΔrHo = the enthalpy change of the reaction - means change sign Q = heat energy transferred to or from the water n = the amount (in moles) of a particular substance

J → kJ NB ΔrHo will be given in kJmol-1 but Q will be calculated in J

Divide by 1000

ΔfHo (standard enthalpy (heat) of formation)

The energy released or absorbed when 1 mol of a substance is formed from its constituent elements at STP

ΔcHo (standard enthalpy (heat) of combustion)

The energy released when 1 mol of a substance burns completely in oxygen at STP

HOFBrINCl

Common elements that exist as diatomic molecules ie H2, O2, F2, Br2, I2, N2, Cl2

ΔfHo (element) = ?

0

Phrases to use with entropy explanations

disorder/ randomness Dispersal of matter & energy

What to look for in entropy of the system

Changes of state Number of particles

Enthalpy vs Entropy

Enthalpy - Energy (heat) Entropy - disorder/ randomness

What to look for in entropy of the surroundings

Whether the reaction is exothermic or endothermic

Entropy of surroundings when the reaction is exo

The particles in the surroundings gain kinetic energy so disorder increases

Entropy of surroundings when the reaction is endo

The particles in the surroundings lose kinetic energy so disorder decreases

When is the reaction spontaneous?

When the entropy of the universe (system + surroundings) increases

Word to use when one entropy increases but another decreases

"outweighs"

Silver ion

Ag+

Lead ion

Pb2+

Barium ion

Ba2+

Magnesium ion

Mg2+

Calcium ion

Ca2+

Zinc ion

Zn2+

Nickel ion

Ni2+

Copper ion

Cu2+

Aluminium ion

Al3+

Hydroxide ion

OH-

Fluoride ion

F-

Chloride ion

Cl-

Bromide ion

Br-

Iodide ion

I-

Sulfate ion

SO42-

Chromate ion

CrO42-

Carbonate ion

CO32-

Equation for calculating the new concentration after two solutions have been mixed

cnew = (cold x vold)/vnew

Qs < Ks Will a ppt form?

No

Qs > Ks Will a ppt form?

Yes

When equal volumes of two solutions are combined, what happens to their concentrations?

They are halved.

Which e-'s do we use to calculate the size of the e- cloud for tda's?

All of them (use smaller number next to the element symbol)

NH3

weak base (molecular)

NH3 + H2O ⇌ NH4+ + OH-

HNO3

Strong acid

HNO3 + H2O → H3O+ + NO3-

KOH

Strong base

KOH → K+ + OH-

HCl

Strong acid

HCl + H2O → H3O+ + Cl-

HBr

Strong acid

HBr + H2O → H3O+ + Br-

H2SO4

Strong acid

NaOH

Strong Base

NaOH → Na+ + OH-

NH4+

Weak acid

(Non-neutral salt)

Ch3COO-

Weak base

(Non-neutral salt)

CH3NH3+

Weak acid

(non-neutral salt)

HCO3-

Weak base

(non-neutral salt)

F-

Weak base

(non-neutral salt)

Ch3COOH

Weak acid (molecular)

HF

Weak acid (molecular)

CH3NH2

Weak base (molecular)

Conductivity (str. acid, str. base, salt)

Full dissociation

high [ions]

good conductors

Strong (acid)

Fully dissociates in water

Acids

Proton donor (Increases [H3O+] in water)

Conductivity (wk acid, wk base)

Partially dissociates

Low [ions]

Poor conductors

Proton

H+ or H3O+

Conductivity depends on

[ions]

pH (str. base)

Fully dissociates

High [OH-]

Low [H3O+]

High pH

Amphiprotic

a species that can donate or accept a proton

Weak (acid)

Partially dissociates in H2O

Bases

Proton acceptor

pH (str. acid)

Fully dissociates

High [H3O+]

Low pH

pH (wk. acid)

Partially dissociates

Lower [H3O+]

Higher pH

Conjugate acid/base pairs

Species that differ by 1xH+

Don't include water when...

It's a Salt or a Strong Base