Chemistry paper2

• Rate of reaction is the change in a quantity divided by time
• Quantity can be the reactant used or product formed
• Experiment: Reacting hydrochloric acid and sodium thiosulfate in a conical flask over a cross
• Increased turbidity indicates the product formed
• Graph of gas volume produced has quantity on y-axis and time on x-axis
• Rate can be increased by:

  • Increasing concentration of reactants in solution
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants (crushing into a powder)
  • Increasing temperature, particles move more quickly and collide with more energy
  • Adding a catalyst reduces activation energy
• Reversible reactions can go back to original reactants once products are made
• Example: Haber process - hydrogen and nitrogen make ammonia, which can break down back into separate gases
• Equilibrium reached when rates of forward and reverse reactions are the same
• Le Chatelier's principle: If a system at equilibrium is changed, the system will adjust to counteract that change
• Changing pressure, temperature, concentration or surface shifts equilibrium position
• Increasing temperature favors endothermic reaction, higher energy input
• Endothermic reactions require energy input, exothermic reactions release energy
• Breaking down of reactant is endothermic, in reversible reactions forward and reverse reactions have opposite energy changes
• Organic compounds have carbon forming the backbone of molecules
• Crude oil consists mostly of hydrocarbons (carbon and hydrogen atoms)
• Alkanes are chains of single covalently bonded carbon atoms with hydrogen atoms
• General formula for alkanes: CNH2N+2
• Fractional distillation separates crude oil into different length alkanes based on boiling points
• Longer alkanes have higher boiling points and are more viscous, shorter alkanes are more flammable
• Alkanes can be used as fuel, solvents, lubricants, detergents, and to make polymers
• Polymers are made from alkenes, which have a carbon-carbon double bond
• Alkenes can be tested with bromine water to show unsaturation
• Cracking breaks longer alkanes into shorter alkanes and alkenes
• Alcohols have an O functional group, names end with -ol
• Alcohols can combust to produce carbon dioxide and water
• Oxidizing alcohols without combustion produces carboxylic acids
• Polymers are long-chain alkanes made from repeating monomers
• Polymerization of alkenes to make polymers
• Condensation polymerization joins monomers with two functional groups
• Amino acids are building blocks of proteins, polymerized to make polypeptides
• DNA is made from nucleotides, starch is a natural polymer
• DNA is made from two polymers that spiral around each other in a double helix
• DNA is made from four different monomers called nucleotides
• Starch is a natural polymer with glucose as the monomer
• Cellulose is a polymer made from beta glucose
• Proteins have amino acids as their monomers
• Melting point or boiling point can be used to determine if a substance is pure
• Formulation is a mixture designed for specific purposes with specific quantities of substances
• Chromatography is used to separate substances in a mixture