CSEC Chemistry flashcards
CSEC 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.
- Mole definition
- The amount of substance containing as many elementary entities as there are atoms in exactly 12 g of carbon-12, namely 6.02 × 10²³ particles.
- Molar volume at STP
- One mole of any gas occupies 22.4 dm³ at standard temperature and pressure (273 K and 1 atm), allowing gas volumes to be converted to moles.
- Relative atomic mass
- The weighted average mass of the naturally occurring isotopes of an element compared with one-twelfth the mass of a carbon-12 atom.
- Empirical formula
- The simplest whole-number ratio of atoms of each element in a compound, obtained by dividing moles of each element by the smallest value.
- Limiting reagent
- The reactant that is completely used up first and therefore determines the maximum amount of product formed in a reaction.
- Percentage yield
- Actual yield divided by theoretical yield, multiplied by 100; less than 100 percent because of side reactions, incomplete reaction, or losses in handling.
- Brønsted–Lowry acid
- A proton (H⁺) donor. A Brønsted–Lowry base is a proton acceptor; every acid has a conjugate base formed after it loses a proton.
- Strong versus weak acid
- A strong acid ionises completely in water (HCl, HNO₃); a weak acid ionises only partially (CH₃COOH), giving lower [H⁺] and higher pH at equal concentration.
- pH formula
- pH = −log₁₀[H⁺], where [H⁺] is concentration in mol/dm³. A change of one pH unit means a tenfold change in hydrogen ion concentration.
- Titration calculation
- At the end point, moles of acid and base relate by the balanced equation; use c₁V₁ divided by c₂V₂ equals the ratio of coefficients.
- Oxidation in redox
- Loss of electrons or an increase in oxidation number. Reduction is the opposite; the two always occur together in a redox reaction.
- Oxidising agent
- A species that accepts electrons from another substance, causing that substance to be oxidised while the agent itself is reduced.
- Electrolysis electrode products
- At the cathode cations gain electrons (reduction); at the anode anions lose electrons (oxidation). In electrolysis the anode is the positive electrode.
- Reactivity series application
- More reactive metals displace less reactive ones from solutions; in electrolysis, ions of less reactive metals are preferentially discharged at the cathode.
- Ionic bonding
- Electrostatic attraction between oppositely charged ions formed by electron transfer, typically between a metal and a non-metal; high melting point and conducts when molten or dissolved.
- Covalent bonding
- A bond formed by sharing one or more pairs of electrons between atoms, usually non-metals; molecules have low melting points and generally do not conduct electricity.
- Metallic bonding
- A lattice of positive ions surrounded by delocalised electrons; explains electrical and thermal conductivity and the malleability of metals.
- Isotopes
- Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers but identical chemical properties.
- Le Chatelier's principle
- When a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, it shifts in the direction that opposes the change.
- Effect of catalyst
- A catalyst lowers the activation energy by providing an alternative pathway, increasing the rate of both forward and reverse reactions without altering the equilibrium position.
- Endothermic versus exothermic
- Exothermic reactions release heat to the surroundings (ΔH negative); endothermic reactions absorb heat (ΔH positive), and the surroundings cool.
- Homologous series
- A family of organic compounds with the same general formula and functional group, showing a gradual change in physical properties and similar chemical reactions.
- Alkene addition reaction
- Alkenes have a C=C double bond and undergo addition, for example decolourising bromine water from orange-brown to colourless, which tests for unsaturation.
- Esterification
- A carboxylic acid reacts with an alcohol in the presence of a concentrated acid catalyst to form an ester and water; esters have characteristic fruity smells.
- Fermentation of glucose
- Yeast enzymes convert glucose to ethanol and carbon dioxide under anaerobic conditions: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂; temperature must be moderate to keep enzymes active.
- Cracking
- Breaking long-chain hydrocarbons into shorter, more useful alkanes and alkenes using heat and a catalyst; produces alkenes for polymerisation.
- Polymerisation
- Addition polymerisation joins alkene monomers through the double bond; condensation polymerisation joins monomers with the loss of a small molecule such as water.
- Hard versus soft water
- Hard water contains dissolved calcium and magnesium ions, forms scum with soap, and produces scale on heating; softened by ion exchange or boiling (temporary hardness only).
- Greenhouse gases
- Gases such as carbon dioxide, methane, and water vapour that absorb infrared radiation emitted by the Earth, contributing to global warming.
- Allotropes of carbon
- Different structural forms of the same element: diamond (tetrahedral, hard, non-conducting), graphite (layers, conducts, lubricant), and fullerenes (cage molecules).
- Electron configuration rule
- Electrons fill shells from lowest energy: 2, 8, 8 for the first twenty elements; the group number equals outer-shell electrons and the period equals the number of shells.
- Tests for gases
- Carbon dioxide turns limewater milky; oxygen relights a glowing splint; hydrogen gives a 'pop' with a lighted splint; chlorine bleaches damp litmus paper.