Separate Chemistry 1

• Properties of transition metals.

  High melting point, high density, form coloured compounds, transition metals and their compounds can be used as catalysts.
• What causes corrosion?

  Oxygen reacts with the metals to form a metal oxide.
• Why is corrosion a redox reaction?

  The metal loses electrons so is oxidised, oxygen gains electrons so is reduced.
• How can oxygen and water be excluded to prevent iron rusting?

  Paint the metal, coat it in oil/grease, cover the metal in plastic, kept the metal in a vacuum.
• Sacrificial protection.

  Galvanised with a more reactive metal so it will corrode instead.
• Electroplating.


  A process in which a metal is coated with a layer of another metal.
• Electroplating process.

  Metal being coated at the cathode, the coating metal at the anode. The electrolyte must contain ions of the coating metal.
• What is an alloy?

  A mixture of two or more metals or a metal and another element.
• Why is iron alloyed to make alloy steels?

  It is relatively brittle. Low carbon steel - Malleable so used for sheeting. High carbon steel - Hard so used for cutting tools. Stainless steel - Corrosion resistant so used for cutlery.
• Why is a cooper used in electrical cables?

  Ductile and a very good electrical conductor.
• Why is aluminium used for aircraft parts?

  Low density.
• Why is gold used for jewellery?

  Very unreactive so resistant to corrosion, appearcne won’t be affected overtime.
• Magnalium.


  Alloy of magnesium and aluminium, lighter and stronger than aluminium and more resistant to corrosion, used for cars and aircraft.
• Brass.


  Alloy of copper and zinc, hard and resistant to corrosion. Used for decorative hardware like plumbing fittings.
• Concentration (mol/dm3) = moles/volume(dm3)


  Concentration (mol/dm3) = concentration (g/dm3)/Mr
• How do you convert cm3 to dm3?

  Divide by 1000
• Acid-alkali titration to find the concentration of alkali method.

  Rinse the pipette with the alkali solution, use this pipette to add alkali to a conical flask. Add a few drops of phenolphthalein, rinse and and fill the beaker with acid. Gradually add the acid until the alkali solution turns colourless, repeat and use results to calculate a mean titre and the concentration of alkali.
• If you know the volume of acid required to neutralise an alkali, how could you calculate the concentration of the acid, given the alkali concentration and volume?


  Calculate the number of moles of the alkali, use the chemical equation to work out the ratio of acid and alkali then find the moles of acid, divide the moles of acid by the volume used in neutralisation to find concentration.
• Theoretical yield.


  The amount of product that would be collected under perfect reaction conditions.
• Percentage yield calculation.


  (Percentage yield/theoretical yield) x 100
• Why could the actual yield be less than expected?

  Incomplete reaction, competing, unwanted side reactions, practical losses/human error, for example some solid may get lost when being transferred between beakers.
• Atom economy of a reaction.

  A measure of the efficiency of the reaction,

  Atomy economy = (Mr of desired product/Mr of reactants)x100
• Why might one reaction pathway be chosen over another?

  Higher atom economy, higher yield, faster rate, equilibrium position favours products more, by products are more useful/less harmful.
• Avogadro’s law.


  At the same temperature and pressure, equal amounts of gas will occupy the same volume.
• What is the molar volume of a gas?

  The volume occupied by one mole of molecules of any gas at room temperature and pressure, 24 dm3.
• What is RTP?

  Room temperature and pressure, 20 degrees, 1 atmosphere.
• Molar volume of gas calculation.

  Molar volume = volume (dm3)/moles of gas
• Steps in the Haber process.

  Obtained gases compressed at 200 atm and heated to 450 degrees, pumped into tank containing layers of catalytic iron beads, ammonia forms, ammonia and unreacted hydrogen and nitrogen pass inot a cooling tank, ammonia collected as liquid and hydrogen and nitrogen recycled back into the tank.
• Why is a catalyst used in the Haber process?

  To increase the rate of reaction so more product is produced quicker.
• Factors that should be considered for industrial reactions.

  Availability and cost of raw materials, energy requirements, optimum temperature and pressure for high yield and fast reaction rate, need for a catalyst.
• What chemical compounds might fertilisers contain?

  Nitrogen, phosphorus and potassium compounds.
• What compounds are found in NPK fertilisers?

  A combination of nitrogen, phosphorus and potassium compounds.
• What does each compound help with?

  Nitrogen - Healthy leaves.

  Phosphorus - Healthy roots.

  Potassium - Growth and healthy fruit/flowers.
• Which ammonium salt is most commonly used for fertilisers?

  Ammonium nitrate
• Salt ammonium nitrate formation equation.

  Ammonia and nitric acid.

  NH3 + HNO3 - NH4NO3
• Chemical equation for the formation of ammonium sulfate from ammonia and sulfuric acid.


  2NH3 + H2SO4 - (NH4)2SO4
• How can ammonium sulfate be prepared in a laboratory?

  Titration between ammonia (alkali) and sulfuric acid. Repeat, adding the exact volumes of reactants without the indicator (as it is an impurity), remove the water by evaporation and crystallisation, leaving pure crystals.
• How can ammonium sulfate be produced on an industrial scale?

  Raw materials obtained from the Haber process (ammonia) and the contact process (sulfuric acid). a larger reactor chamber is filled with ammonia gas, sulfuric acid is sprayed into the chamber from above, ammonium sulfate crystals form.
• Laboratory method

  Faster rate of reaction, small reactant quantities can easily be bought, room temperature and pressure, simple equipment required, very small yield.


  Industrial process

  Very expensive and complex, continuous process so continuous yield, larger volumes of product, slow rate of reaction, higher energy requirement, Haber process needed.
• Chemical cell.

  Two metals of different reactivities are placed in an electrolyte. The more reactive releases electrons, positive charge. The electrons flow to other electrode which become negatively charged, the difference between the electrodes ability to release electrons causes voltage to be produced.