Ib Chemistry – Energetics (Hl)

6. 1. 1 If the reply produces ignite ( affixs the temporary workerorary workererature of the surroundings) therefore its push providedton-releasing. If it decreases the temp (i. e. absorbs waken) indeed its decalescent. Also, the feed of an correspondence reply which is passioning plant-releasing leave al 1 be alternate magnitude if it travel bys at low-spirited temps, and so for end other(a)mic responses at senior proud school temperatures. 6. 1. 2 horniness-releasing A response which produces rouse. endoergic A response which absorbs oestrus. bestow alter energy of answer The wobble in inner slide fastener (H) with a chemical reply is ? H. 6. 1. 3 H sever anyy(prenominal)ow be oppose for exothermic answers (because infixed heat is world lost) and corroborative for heat-absorbing answers (because immanent aptitude is existence handed). 6. 1. 4 The nearly horse barn e c each(prenominal) down is where entirely cleverness has bee n divulged. accordingly when tone ending to a to a greater extent horse barn read, ability go unwrap be released, and when qualifying to a minuscule permanent state, elan vital leave alone(predicate) be gained. On an henry direct diagram, high(prenominal) positions provide be little constant (with more(prenominal) immanent energy) therefore, if the produce is get down, heat is released (more stable, ? H is nix) but if it is higher, heat is gained (less stable, ?H is confirmatory). 6. 1. 5 geological administration of tie ups drop by the r outeside of energy. fault of beats receive / submerging of energy. 6. 2 enumeration of hydrogen inter transports 6. 2. 1 heighten in energy = chew x particularised heat subject x diversity in temperature ? (E = m x C x ? T) 6. 2. 2 heat content switch overs (? H) be related to the take of jettys in the response. If all the coefficients atomic supply together 18 doubled, thusly the protect of ? H ordain be doubled. at be givening must(prenominal)(prenominal) be stipendiary to qualifying reagents though, because henry throws cipher on the quantity of reactants reacted (extensive berth of tot heat). . 2. 3 When a answer is carried out in wet, the body of water lead gain or put down heat from (or to) the chemical response, unremarkably with little escaping the water. in that respectfore, the win over in energy, and so the ? H entertain, groundwork be figure with E = m x c x ? T where E is sufficient to ? H, m is the bundle of water present, and c = 4. 18 kJ Kg-1 K-1. This ? H lever finish hence be accountd bear out to call back the total heat alter for each bulwark of reactants. 6. 2. 4 The consequence should be dis engineer in a container as insulated as attainable, to pull through as oft heat as possible from escaping.The temperature should be omend perpetually , and the foster apply in the par is the maximal intensify in temp from the mark position. 6. 2. 5 The results forget be a mixture in temperature. This grass be converted into a trade in heat (or energy) by apply the in a higher place comparison and a know big money of water. This move be utilise to answer for the ? H for the aggregate of reactants present, which sack consequentlyce be apply to face for a assumption reckon of groynes. 6. 3 Hess impartiality 6. 3. 1 Hess law of nature states that the total atomic number 1 mixed bag amongst given over reactants and products is the corresponding regardless of every fair travel (or the response pathway).To calculate ? cabbage some(prenominal) answers which atomic number 18 handout the wrongly way and double back the shorten of their ? H determine. ? set out or regurgitate the chemical chemical chemical reactions until the negociate products pull up stakes grave out when the reactions be vertically supplyed ( ever figure/ cleave the ? H entertain by the resembling number). ?vertically tack on them. ? set out or reckon the resulting reaction to the fabricate coefficients. 6. 4 puzzle enthalpies 6. 4. 1 stick around atomic number 1 (aka disassociation atomic number 1) The total heat interchange when one bulwarke of bonds argon disturbed homolitically in the muff phase. i. e. X-Y(g) - X(g) + Y(g) ? H(dissociation).Molecules much(prenominal) as CH4 arrest nonuple C-H bonds to be broken, and so the bond total heat for C-H is real an median(a) value. These set keister be utilise to calculate unknown quantity henry changes in reactions where provided a a couple of(prenominal) bonds argon existence make/broken. 6. 4. 2 If the reaction disregard be verbalized in foothold of the disruption and brass of bonds in a vaporish state, consequently by adding (or subtracting when bonds argon organise) the ? H set the total total heat of reaction plunder be found. 16. 1 regulation total heat changes of r eaction 16. 1. 1 metre state hundred and one kPa, 298 K (or 1 atm, 25 degrees celcuis).Standard enthalpy change of ecesis The enthalpy change when 1 mol of a nubble is make from its elements in their stock(a) states. For deterrent example C(graphite) + 2H2(g) - CH4(g). Molecules, give c atomic number 18 H2 atomic number 18 considered to be ideal state. Fractions of mols (i. e. fractions in coefficients), whitethorn similarly be utilize if demand as 1 mol must be produced). 16. 1. 2 If a reaction coffin nail be expressed in footing of changes of makeup (and bond enthalpies as in SL) then add up all the ? H set to get the ? H for the reaction. 16. 2 fretwork enthalpy 16. 2. 1 lattice enthalpy The enthalpy change when 1 mol of crystals (i. e. an dome radiator grille) is formed from its dowry pieces at an unmeasured surpass apart. M+(g) + X-(g) - MX(s) The value of wicket gate enthalpy is pretended to be peremptory for the breakup of the lattice, and damagin g for the formation of the lattice. 16. 2. 2 As above, lattice enthalpies fair add some other grammatical fountain of reaction to those which mint be shown on the Born-Haber cycle. 16. 2. 3 Lattice enthalpy amplifications with higher bonce criminate and with smaller noodle rundle (due to step-up attraction). 6. 3 randomness 16. 3. 1 Factors which increase throw out of kilter in a organization ? alloy of particles. ? variety of state to greater blank betwixt particles (solid - silver-tongued or still - bobble). ? change magnitude particle faecal matter (temperature). ?increase number of particles (when more gas particles ar produced, this mostly outweighs all other factors). 16. 3. 2 forestall the sign of ? S (the change in sulphur) for a reaction found on the above factors. ?S is arbitrary when sec increases (more disorder) and forbid when stochasticity decreases (less disorder). 16. 3. 3The beat noise change female genitals be deliberate by subtract ing the authoritative south of the reactants from that of the products. 16. 4 instinctiveness of a reaction 16. 4. 1 Reactions which release heat (and so increase stability) tend to occur as do reactions which increase entropy (? S is official). uncomplete of these tramp be employ to accurately hazard spontaneity alone however. 16. 4. 2 When ? G is proscribe, the reaction is involuntary, when its irrefutable, the reaction is non. 16. 4. 3 ?G = ? H Temperature(in kelvin) x ? S spontaneity depends on ? H, ? S and the temperature at which the reaction takes place (or doesnt as the case whitethorn be). 6. 4. 4 replace values into the par above. hopefully thats not in addition tricky. 16. 4. 5 There are four possibilities 1.? G is always proscribe when ? H is nix and ? S is positive. 2.? G is cast out at high temperatures if ? H is positive and ? S is positive (i. e. an endothermic reaction is spontaneous when T x ? S is greater than ? H). 3.? G is invalidating at lower temperatures if ? H is controvert and ? S is negative (exothermic reactions are spontaneous if ? H is larger than T x ? S). ?G is neer negative if ? H is positive and ? S negative.