higher chemistry - unit 3

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hydrogen peroxide (34g). Calc volume of oxygen produced when 0.051g of hydrogen peroxide decomposes 2 H₂O₂ +17 →→ 2H1 ₂0 (1) + 0₂ (9) n = 0.051 34 = 0.0015 2 H₂O₂ →→ 2 : 015 V= +0₂ 000 75 0.018 0.00075 X 24 Controlling the rate factors affecting rate of reaction. 4 temperature 4 concentration. 4 pressure + particle size + catalyst 4 concentration - increases no. of particles in Solution •°• increase in successful collisions increasing rate. pressure increase likliness of particles colliding • increase successful collisions & rate particle size - increases surface area .. increases collisions, increasing rate 4 temperature - increases Rinetic energy. collide with more energy & rate. Average rate rate = + r = AQ At time = 1 t Collision Theory for atoms/molecules/particles to react, they must collicle 2 factors required for successful collisions to take place : 4 activation energy La geometry of reactants 10 Rinetic energy greater than the activation energy (EK > Ea) 2 the correct collision geometry (particles to be facing the correct way) Activation minimum amount of energy required energy for particles to collide - Activated high energy, unstable arrangement of complex atoms formed at intermediate stage of reaction. - enthalpy diagrams Chemical energy -AH No. of particles Enthalpy (AH). 2 exothermic Exothermic Endothermic еав ea F AH t сав enclothermic the difference in energy between the reactants and products. reaction which energy is released reaction that takes in heat energy ea with catalyst ea without catalyst Kinetic energy catalyst - increases rate without being used up in the reaction, by lowering activation energy. enthalpy of combustion. • the energy released when one mole of a substance burns completely in oxygen. molar bond enthalpy thermometer Imean bond enthalpy draught shield. bond enthalpies R-P bond breaking = endothermic (tve) bond forming = exothermic (-ve) copper can + water spirit burner energy required to break one mole of bonds in a diatomic molecule in the gaseous state. average energy required to break one mole of bonds for a bond which occurs in a variety of compounds. - flip • used to calculate enthalpy changes to eqn match 2 times -egn tu match Hess's law add all он example Co₂ (1) + 30₂ (9) ((S) + O₂ (g) →→→ S (s) + O₂ (g) + C (S) + 25 (S) H (0₂ (9) + 250₂ (9) CO₂ (9) SO₂ (g) CS₂ (1) C(s) + 25(S) → CS₂ (1) CS₂ (1) + ((S) + 25(S) - 393.5 ·296.8 87.9 1075 ΔΗ 04 S (5) + 0₂ (9) SO₂ (9) 25 (s) + 20₂(g) + 250₂ (9) = - 393.5 -296.8 +87.9 +87.9 -87.9 -296.8 x2 Equilibria only occurs in reversible reactions • used to maximise profit by favouring products. + rate of forward rate of backwards + concentration of reactants/products are constant. Changing equilibria position. ● Concentration increase conc of reactants cecrease conc of reactants increase conc of products decrease cone of products temperature increase temp. decrease temp shifts right. Shifts Left Shifts left shifts right shifts to endothermic shifts to exothermic pressure increase pressure shifts to side with fewer gas moles clecrease pressure shifts to side with most gas moles catalyst increases rate of forward and reverse reaction equally therefore cloesn't affect position. 0 Chemical Analysis cbromatography. used to separate mixtures based on their solubilit and Size types of chromatography. paper gas Paper Chromatography • mobile phase - solvent (thing that moves) Stationary phase-paper (thing that moves on) D retention time time taken for a component to trave through apparatus Size of molecule the larger the molecule the longer it takes to travel