Lesson 7 Energetics Checklist1.Laws of conservation of energy -> Energy cannot be create or destroy. -> Toal amount of energy og a system and its surroundings remains constant.2.-Heat change under constant volume = change in internal energy -Heat change under constant pressure = enthalpy change3. Exothermic reaction is a reaction that gives out heat (surrounding temp. ) Endothermic reaction is a reaction that takes in heat (surrounding temp . )4. Exothermic-> release heat; delta H = -ve (negative sign) (1) Combustion (2) Precipitation(3) Acid-Alkali neutralization (3)reaction between quicklime and water(5) Bond formation Endothermic-> takes in heat; delta H = +ve (positive sign)(1)Cracking (2)Thermal decomposition(3)Reaction between NH4Cl and hydrated Ba(OH)2 (4)Reaction between NH4NO3 and Water(5)Bond breaking 5. Standard enthalpy change -> Conditions temp.=298k/25oC Pressure=1atmConcentration=1MNormal physical state6. Definition- Standard enthalpy change of combustion of a substance is the enthalpy change which one mole of substance is completely burnt in oxygen under standard condition.i.e. C12H22O11 + 12 O2 12 CO2 + 11 H2O- Standard enthalpy change of neutralization of a substance is the enthalpy change which one mole of water is formed form neutralization between an acid and alkali under standard condition.i.e. NaOH + HCl NaCl + H2O

- Standard enthalpy change of solution of a substance is the enthalpy change which one of substance is dissolved in a sufficiently large amount of solvent under standard condition.i.e. NaCl + (aq) Na+ + Cl-- Standard enthalpy change of formation of a substance is the enthalpy change which one mole of substance is formed in the standard physical state under standard condition.i.e. 2 H2 + O2 2 H2O 7. Calculation [ delta H = mc delta T / n ]

8. Hesss LawThe overall enthalpy change of a chemical reaction is the same regardless of the route by which the reaction takes place.9. Chemical reaction rate a. Extremely fast i.e. 2H2 + O2 2H2O b. Rapidly -- i.e. Ag+ + Cl- AgCl c. At a moderate speedi.e. Mg + 2HCl MgCl2 + H2d. Slowly i.e. 4Fe + 3O2 + 2nH2O 2Fe2O3.nH2O10. Average rate of reaction = Total change in amount of product (or reactant) / total time taken11. Effective Collision Reactant particles are moving at different speeds only a small fraction of collisions is successful in forming products. Those collisions resulting in a chemical reaction are call effective collisions. 12. Quenchinga)+ice-water(cooling) b) H+ added c) removing the catalyst (if it is needed)13. Reaction rate (k) directly proportional to (no. of effective collisions / time taken)

14. Example of answering question As CO2 is formed as the only gaseous product, we can carry out the reaction in a closed system. The increase pressure inside the apparatus at different times can be monitored by using a pressure sensor connected.15. Measurement ConcentrationCH3COOH+NaOH CH3COONa+CH3OHQuenched-Measure the change in concentration by titration

Gas volumeMg + 2HCl MgCl2 + H2On-going-Measure the change in volume of H2 gas with a gas syringe

Gas pressure Mg + 2HCl MgCl2 + H2On-going-Measure the change of pressure of the system with a pressure senorn/a

Mass CaCO3 +2HCl CaCl2+CO2+H2OOn-goingMeasure the change in mass of reaction mixture with electronic balance

Color Intensity2MnO4-+5C2O42-+16H+ (60oC)2Mn2++8H2O+10CO2On-going-Measure the change in color intensity of reaction with colorimetern/a

Transmittance of lightS2O3-+2H+ SO2+H2O+SOn-goingMeasure the time taken for the blot out of the cross using stop watchn/a

16. Avogadros law: Equal volume of all gases of the same temp. and pressure contain the same no. of molecule(no. of mole). (no. of mole = volume/24 dm3 )17. Explanation of effect of concentration/pressure/temp on reaction rate(a) Concentration/pressure: pressure increase->volume decrease->[reactant] increase -> effective collision increase -> rate increase(b) Temperature: temp. increase -> average K.E. increase -> speed of particles increase -> effective collisions increase -> rate increase(c) Surface area of solid reactants: surface increase-> chance to collide-> effective collision increase-> rate increase(d) Catalyst: positive catalyst : rate increase ; negative catalyst : rate decrease => give an alternative energy routs or profilee.g. 2 H2O2 2 H2O + O2 (MnO2 +ve catalyst; H+ -ve catalyst)

18. Equilibrium can only be established in a closed system. rate of forward reaction = rate of backward reaction At equilibrium, [P] and [R] remain unchanged : No observable change19. Kc equilibrium constant-> a ratio with a constant value at a given temperature.Homogeneous equilibrium All the reactants and products are in the same phrase.Heterogeneous equilibrium Two or more phases are present.20. Irreversible reactions: chemical reactions proceeding in one direction only. 4 Fe + 3 O2 + 2n H2O 2 Fe2O3 . n H2O Reversible reactions: chemical reaction proceeding in either direction depending on the condition.CaCO3 CaO + CO2