Developing fuels

• Where is the energy transfer for endothermic reactions? How can we observe endothermic reactions?

  energy transferred from surroundings to system

  observed through a increase in temp of the system and decrease in temp of the surroundings
• How to find the empirical formula?

  1. divide each percentage by atomic mass

  2. divide each by the smaller one

  3. find lowest whole number ratio by rounding up or by multiplying up
• What does endothermic mean?


  more energy is used when breaking bonds of the reactants than is released when making bonds of the products
• What is an example of the name of a structure with 2 double bonds?

  buta-1,3-diene
• What does exothermic mean?


  more energy is released when making bonds in products than is used when breaking the bonds of the reactants
• Where is the energy transferred in exothermic reactions? How can we observe exothermic reactions?


  energy transferred from system to surroundings

  observed through a decrease in temp of system and an increase in temp of surroundings
• What does Hess' Law state?

  that bond enthalpy is the same which ever way you make the products
• What does the enthalpy change show?


  the quantity of energy transferred to and from the surroundings during a chemical reaction in an open container
• What are the values for enthalpy change of an exothermic reaction always? Why?


  negative because energy has been lost (from the system to the surroundings)
• What are the values for enthalpy change of an endothermic reaction always? Why?

  positive because energy has been gained (from the surroundings to the system)
• What conditions do enthalpy change depend on?

  temperate

  pressure

  concentration of solutions
• What are the standard conditions?


  298 kelvin (25°c)

  standard pressure of 1 atmosphere

  a standard concentration of 1moldm⁻³
• How do you convert from °c to kelvin?

  add 273
• How do you convert from kelvin to °c

  subtract 273
• What is absolute zero?

  0 kelvin
• What is the definition of the standard enthalpy of formation?

  when 1 mole of a compound is formed from its constituent elements in their natural states under standard conditions
• What is the symbol for the standard enthalpy of formation?


  ∆H⁰f₂₉₈
• What is the definition of the standard enthalpy of combustion?

  when 1 mole of substance is burned completely in standard conditions
• What is the symbol for the standard enthalpy of combustion?


  ∆H⁰c₂₉₈
• What is the definition of the standard enthalpy of reaction?


  when molar quantities of reactants (as stated in the equation) react together under standard conditions
• What is the symbol for the standard enthalpy of reaction?


  ∆H⁰r₂₉₈
• What is the definition of the standard enthalpy of neutralisation?

  when 1 mole of hydrogen ions react with 1 mole of hydroxide ions to form 1 mole of water under standard conditions
• What are the homologous series?

  alkanes

  alkenes

  cycloalkanes

  alcohols
• what is an ether?

  an oxygen atom bonded to 2 alkyl groups
• what is the general formula of an alkane?

  CnH₂n+₂
• What is the general formula for an alkene?

  CnH2n
• What is the general formula for cycloalkanes?

  CnH₂n
• What are aliphatic compounds?

  organic compounds in which carbon atoms form open chains and not aromatic rings
• What are aromatic compounds?


  organic compounds containing one or more benzene rings
• What are arenes?


  a group of aromatic compounds that contain benzene rings
• What is the symbol equation to find the energy transferred?

  E = mc∆T
• What is the word equation to find the energy transferred with units?


  energy transferred (J) = mass water (g) x specific heat capacity x temp change (°c)
• What is the value of specific heat capacity?


  4.18 (J/g/°c)
• What are the potential errors in practical combustion experiments?


  1. incomplete combustion

  2. heat loss to surroundings

  3. evaporation of fuel from the wick

  4. heat loss to calorimetre
• what is the equation to find the percentage error/ uncertainty?

  % error = value of uncertainty/ value of substance measured x 100
• What is needed for E/Z isomerism to occur?

  each carbon at either end of the carbon-carbon double bond must be bonded to 2 different groups
• What is a cis isomer?


  highest priority groups on the same side of the double bond. Must have 2 hydrogen atoms and 2 non-hydrogen atoms/groups
• What is a trans isomer?


  highest priority groups on different sides of the double bond. Must have 2 hydrogen atoms and 2 non-hydrogen atoms/groups
• When naming E/Z isomers, what has first priority and what has second priority?


  heavier molecules have first priority, lighter molecules have second priority
• What is an E isomer?


  higher priority groups on different sides of the double bond. Must have 1 hydrogen atom, 3 non-hydrogen atoms/groups