chem sac 2

• less energy required to break hydrogen bonds means the energy efficiency of black coal is greater than brown coal
• biofuels are derived from plants and animals
• biofuels are renewable
• fuels are substances that release stored energy easily. energy which is released through combusion
• carbon neutral is when there is no net production of carbon dioxide (excluding processing). carbon dioxide is absorbed and released at the same rate
• positive delta H means endothermic
• negative delta H means exothermic
• if mol is doubled, then delta H is doubled
• if equation is reversed, delta H sign change (same magnitute)
• endothermic reactions absorb energy
• exothermic reactions release energy
• activation energy is the threshold that needs to be overcome for the reaction to take place (required to break bonds of reactants)
• in endothermic reaction the products are higher than the reactants
• in exothermic reactions the product is lower than the reactants
• combustion is when a substance reacts with oxygen, releasing energy
• non-renewable means a fuel is used up faster than they can be replaced
• renewable fuels are replaced ay a sustainable rate (faster or at the same rate theyre being used up)
• equilibrium is when the foward and backward reactions are equal
• Q = K at equilibrium
• when the equation is reversed, K becomes a reciprocal of itself
• if an equation is multiplied by x. then K is the is K to the power of x
• if the equation is divided by x. then K is K to the power of 1/x
• molar enthalpy is the enthalpy given per mol
• photosythesis is an endothermic reaction
• cellular respiration is an exothermic equation
• photosynthesis is. 6CO2+6H20->C6H12O6+O2
• complete combustion is in excess oxygen
• incomplete combustion is in limited oxygen
• heat of combustion is the heat energy released when a certain amount of substance burns completely
• heat of combustion should be a positive value (measured from the surrounding) for combustion
• enthalpy is measured from the system
• a prerequisite for dynamic equilibrium is a closed system
• K is the ratio of concentration of products to concentration of reactants at equilibrium
• if reactants are solid or liquid or pure, they have a concentration of 1
• K and Q are = c(products)/c(reactants)
• catalysts provide an alternate pathway with a lower activation energy
• only temperature and catalyst directly impact number of successful collisions (lower activation energy)
• the only thing that changes the value of K is temperature