SACE Stage 2 Chemistry flashcards
SACE Stage 2 Chemistry · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- ppm concentration
- For dilute aqueous solutions, one part per million equals about one milligram of solute per litre of solution when density is 1.00 kg/L.
- pH formula
- pH equals the negative base-10 logarithm of the hydronium-ion concentration; at 25 °C, pH plus pOH equals 14.
- strong versus weak acids
- Strong acids ionize completely in water, whereas weak acids only partially ionize and have an acid dissociation constant, Ka, smaller than one.
- acid deposition
- Sulfur and nitrogen oxides released by combustion react with water and oxygen to form sulfuric and nitric acids, lowering rain pH below about 5.6.
- greenhouse gas property
- A greenhouse gas absorbs infrared radiation emitted by Earth and re-emits energy, warming the troposphere; examples include carbon dioxide, methane, nitrous oxide and water vapour.
- biochemical oxygen demand
- BOD measures oxygen consumed by microorganisms decomposing organic matter in water; a high BOD indicates organic pollution and possible oxygen depletion.
- calibration curve
- A calibration curve plots instrument response against known standard concentrations; unknown concentrations are read from the fitted line after blank correction.
- combustion equation
- A hydrocarbon CxHy burns completely in oxygen to produce carbon dioxide and water: CxHy + (x + y/4)O2 → xCO2 + (y/2)H2O.
- collision theory
- Reaction particles must collide with energy at least equal to the activation energy and with suitable orientation for a successful reaction.
- rate units
- Reaction rate is the change in concentration of a reactant or product divided by the time interval; common units are mol L^-1 s^-1.
- equilibrium constant Kc
- For aA + bB ⇌ cC + dD, Kc equals [C]^c[D]^d divided by [A]^a[B]^b at equilibrium; it depends on temperature.
- reaction quotient Q
- Q has the same form as Kc but uses current concentrations; if Q < Kc the forward reaction is favoured, if Q > Kc the reverse is favoured.
- Le Chatelier principle
- When a system at equilibrium is disturbed by concentration, pressure or temperature change, it shifts in the direction that partially opposes the disturbance.
- Haber process conditions
- Nitrogen and hydrogen combine reversibly to form ammonia in an exothermic reaction; industrial conditions use about 400–500 °C, 150–250 atm and an iron catalyst.
- catalyst effect
- A catalyst lowers activation energy by providing an alternative pathway; it increases both forward and reverse rates and does not change equilibrium position or enthalpy change.
- atom economy
- Atom economy equals the molar mass of desired product divided by the total molar mass of all reactants, multiplied by 100 percent.
- IUPAC suffix priority
- When naming, the principal functional group determines the suffix; priority generally decreases from carboxylic acid to ester, amide, aldehyde, ketone, alcohol, amine, alkene and alkyne.
- chiral carbon
- A chiral carbon is sp3 hybridized and bonded to four different groups, producing non-superimposable mirror-image molecules called enantiomers.
- esterification reaction
- A carboxylic acid reacts with an alcohol in the presence of an acid catalyst to form an ester and water in a reversible condensation reaction.
- primary alcohol oxidation
- A primary alcohol can be oxidized to an aldehyde and then to a carboxylic acid; a secondary alcohol oxidizes to a ketone, while tertiary alcohols resist oxidation.
- peptide bond
- A peptide bond forms by condensation between the amine group of one amino acid and the carboxyl group of another, releasing water.
- protein denaturation
- Denaturation disrupts secondary and tertiary protein structure by heat, pH change or chemicals, usually without breaking peptide bonds, reducing biological function.
- saponification
- Triglycerides react with sodium hydroxide to produce glycerol and soap molecules, which are sodium salts of long-chain fatty acids.
- DNA base pairing
- In DNA, adenine pairs with thymine using two hydrogen bonds, and cytosine pairs with guanine using three hydrogen bonds.
- calorimetry equation
- Heat energy absorbed or released equals mass times specific heat capacity times temperature change: q = mcΔT, with q in joules.
- enthalpy of combustion
- The enthalpy of combustion is the heat released when one mole of a substance burns completely in oxygen under specified conditions; it is usually negative.
- Hess's law
- The enthalpy change of a reaction depends only on initial and final states, so enthalpy changes of step reactions can be added to find the overall change.
- galvanic cell electrodes
- In a galvanic cell, oxidation occurs at the anode, reduction occurs at the cathode, and electrons flow through the external circuit from anode to cathode.
- electrolysis definition
- Electrolysis uses an external electrical energy source to drive a non-spontaneous redox reaction; oxidation occurs at the anode and reduction at the cathode.
- hydrogen fuel cell
- A hydrogen–oxygen fuel cell produces electrical energy and water; it has high efficiency and no carbon dioxide emission at the point of use.
- water treatment steps
- Conventional water treatment may include coagulation, flocculation, sedimentation, filtration and disinfection by chlorination or ultraviolet light.
- recycling aluminium
- Recycling aluminium requires much less energy than extracting it from bauxite by electrolysis, reducing resource use and greenhouse gas emissions.