Chem

• Law of Conservation of Energy


  Energy can either be created or destroyed. It can be transferred between the system and surroundings.
• ΔEsys=-ΔEsurr is the equation of?

  Law of Conservation of energy
• The negative sign indicates the flow of energy.
• the first law of thermodynamics states that in any process, the change in energy of a system is equal to the heat absorbed (q) by the system and the work done on it.
• Work is positive (+w) when work is done on the system, it also gains energy.
• Work is negative (-w) when the system does the work, it uses up or transfers some of its energy.
• When the system absorbs heat the q is (+q) and when the system release heat to surroundings it will be (-q).
• Thermochemical Equation indicates the physical state of the reactants and products involved in the reaction.
• Enthalpy (H) is a form of chemical energy. It indicates the amount of heat absorbed or released by a chemical reaction at constant atmosphere pressure.
• Enthalpy of reaction (delta H) is the difference of between the enthalpy of products and reactants.
• ΔH is positive when the chemical reaction is endothermic, while negative when the reaction is exothermic.
• The standard molar enthalpy of reaction (ΣΔHorxn) can be calculated by subtracting the sum of the enthalpies of formation of the products and the sum of the enthalpies of formation of reactants.
• Chemical Kinetics is the study of rates of chemical processes that includes reaction mechanisms and how different factors affects it.
• The rate of reaction is a change in amount or concentration of a substance (reactant or product) per unit time.
• Collision Theory states that the rate of a chemical reaction is proportional to the number of collisions between reactant molecules.
• Only a small fraction of the collisions are effective collisions.
• Effective Collision = New Product
• To produce an effective collision, reactant particles must possess some minimum amount of energy used to initiate the reaction called activation energy.
• The larger the sample, the greater the number of effective collisions, and the faster the rate of reaction.
• The number of particles possessing enough energy is dependent on the temperature of the reactants.
• If the reactant particles do not possess the required activation energy when they collide, they bounce off each other without reacting. True or False?

  True
• Some chemical reactions also require that the reactant particles must be in a proper orientation to produce an effective collision.
• To have an effective collision, the reactants must collide with each other. True or False?

  True
• There can be an effective collisions whatever the orientation of the molecules. True or False?

  False
• To have an effective collision, the molecules must have sufficient activation energy to initiate the reaction. True or False?

  True
• System - a definite area where thermodynamic processes may take place.
• Surrounding - the area or region outside the system.
• Universe - the system plus the surroundings.
• Thermodynamics studies how changes in energy, entropy, and temperature affect the spontaneity of a process or chemical reaction.
• Spontaneity is a spontaneous process that occurs without outside intervention.
• A reaction is said to be spontaneous if it favors the formation of the products at the conditions under which the reaction is occurring. True or False?

  True
• Reaction occurs if there is a decrease in enthalpy and an increase in the entropy of the system.
• Enthalpy is the thermal energy stored in a system.
• Enthalpy Change, ∆H is the thermal energy change at a standard condition.
• Entropy ∆S, is a measure of randomness or disorder.
• The greater the disorder of the system, the greater its entropy.
• The value of entropy depends on the state of the system. Particles in gas phase are more disorderly compared to those in liquid phase which results in a positive ∆S.
• The SI unit of entropy is Joules per Kelvin (J/K).
• We can express entropy as ∆S= qrev/T wherein ∆S is the entropy, qrev is the heat and T is the temperature in Kelvin.