U2 Exam

Hydrogen Bonding

H2O forms strong intermolecular hydrogen bonds.

Boiling Point of Water

This explains its unusually high boiling point compared with other Group 16 hydrides.

Density of Ice

has an open hydrogen-bonded lattice, so it is less dense than liquid water.

Specific Heat Capacity of Water

Water has a high specific heat capacity: 4.18 J g^-1 K^-1.

Latent Heat of Vaporisation

High latent heat of vaporisation means evaporation removes lots of energy.

Acid

H+ donor.

Base

H+ acceptor.

Strong vs Weak Acids

essentially complete ionisation/dissociation; partial ionisation

Concentration vs Strength

Concentrated/dilute describe amount per volume, NOT strength.

Amphiprotic

can donate or accept H+.

Polyprotic Acid

can donate more than one H+.

Neutralisation Reaction

H+(aq) + OH-(aq) -> H2O(l).

Acid and Carbonate Reaction

Acid + carbonate -> salt + CO2 + H2O.

pH Formula

pH = -log10[H+].

Water Ion Product

At 25 deg C: Kw = 1.0 x 10^-14 and pH + pOH = 14.00.

OIL RIG

Oxidation Is Loss; Reduction Is Gain of electrons.

Oxidant

accepts electrons and is reduced.

Reductant

donates electrons and is oxidised.

Anode and Cathode

Anode = oxidation; cathode = reduction.

Electron Flow

Electrons flow through the external circuit from anode to cathode.

Displacement Reaction

More reactive metal can displace ions of a less reactive metal.

Acidic Redox Balancing

Balance non-O/H atoms -> O with H2O -> H with H+ -> charge with e- -> cancel electrons.

Concentration Formula

c=n/V, with V in L.

Mass Concentration

Mass concentration = m/V.

Percentage Concentration (m/v)

%(m/v) = g per 100 mL.

Percentage Concentration (v/v)

%(v/v) = volume solute / volume solution x 100.

Dilute Aqueous ppm

Dilute aqueous ppm approx mg L^-1.

Solubility and Temperature

Many solids become more soluble as temperature rises, but always read the actual graph.

Gas Solubility and Temperature

Gas solubility usually decreases as temperature rises.

Precipitation

Precipitation removes dissolved ions by turning them into an insoluble solid.

Dilution Formula

c1V1=c2V2.

Equivalence Point

exact stoichiometric point.

Endpoint

observed indicator colour change.

Calculation Pathway

known cV -> moles -> mole ratio -> unknown moles -> concentration.

Suitable Indicator

changes colour near the equivalence point.

Standard Laboratory Conditions (SLC)

25 deg C / 298 K and 100 kPa.

Ideal Gas Law

pV=nRT.

Ideal Gas Constant

With kPa and L: R=8.31 kPa L mol^-1 K^-1.

Temperature Conversion

Always convert deg C to K.

Approximate Ideal Molar Volume

= 24.8 L mol^-1.

Greenhouse Gases

CO2, CH4 and H2O vapour contribute to greenhouse effects because they absorb infrared radiation.

Hydrate Analysis

heat -> find mass of water lost -> convert salt and water to moles -> simplest ratio.

Conductivity and Ion Concentration

Higher dissolved ion concentration generally means higher conductivity.

Calibration Curve

measure unknown response and use graph/equation to find concentration.

Colorimetry vs UV-visible Spectroscopy

Colorimetry uses visible light; UV-visible spectroscopy uses UV and/or visible absorption.

Resolution

smallest detectable/displayed change.

Validity

method actually tests the intended question.

Random Error

Random error causes scatter; repeats help.

Systematic Error

Systematic error causes consistent bias; repeats do not fix it.

Law

describes a consistent relationship/pattern.