Separate chemistry 1

• What are most metals classified as?

  Transition metals
• What are the typical properties of transition metals?

  High melting point, high density, formation of coloured compounds, and catalytic activity
• What is one example of a transition metal that exhibits catalytic activity?

  Iron
• Why do transition metals have high melting points?

  Due to electrostatic forces of attraction between positively charged metal ions and the 'sea' of electrons
• What is a characteristic of transition metals regarding their ions?

  They have ions with many different charges
• What is corrosion?

  Destruction of materials by chemical reactions with substances in the environment
• What is required for iron to rust?

  Both air and water
• What is the process of rusting in iron?

  Oxidation, which is the gain of oxygen resulting in corrosion
• How can rusting of iron be prevented?

  • Exclusion of oxygen and water
  • Methods include:
  • Painting
  • Coating with plastic
  • Using oil or grease
• How does aluminium protect itself from corrosion?

  It has an oxide coating that excludes oxygen and water
• What is a desiccant used for in preventing rust?

  To absorb water vapor and keep it away from metals
• How can oxygen be kept away from metals to prevent rusting?

  By storing the metal in a vacuum container
• What is sacrificial protection in rust prevention?

  Using a more reactive metal that rusts first to protect the desired metal
• What metal is commonly used for galvanizing iron?

  Zinc
• What is the purpose of electroplating metal objects?

  • Acts as a barrier to exclude oxygen and water
  • Improves appearance by using unreactive metals like gold
• How is electroplating performed?

  Using the metal to be plated as the cathode and the plating metal as the anode in a solution containing ions
• Why are pure metals often converted into alloys?

  • To increase strength and hardness
  • Pure metals are often too soft for everyday use
• How does the structure of pure metals differ from that of alloys?

  Pure metals have uniform ion sizes allowing layers to slide easily, while alloys have different sized ions disrupting this structure
• What are the components of steel?

  Mixtures of carbon and iron
• What is the use of low-carbon steels?

  They are easily shaped and used for sheeting
• What are high-carbon steels used for?

  They are hard and used for cutting tools
• What is the characteristic of stainless steels?

  They are resistant to corrosion and contain chromium and nickel
• How are the properties of metals related to their uses? Give examples.

  • Aluminium: low density, used for aircraft
  • Copper: good conductor, used in electrical cables
  • Gold: good resistance to corrosion, used in jewelry
  • Magnalium (aluminium + magnesium): low density, used in cars and planes
  • Brass (copper + zinc): hard, resistant to corrosion, used in coins
• How is the concentration of a solution measured?

  In moles per given volume of solution, e.g., mol/dm³
• What is the formula to calculate moles of solute in a given volume of a known concentration?

  moles = concentration x volume
• What effect does a smaller volume or larger number of moles of solute have on concentration?

  It gives a higher concentration
• What effect does a larger volume or smaller number of moles of solute have on concentration?

  It gives a lower concentration
• How do you convert concentration from g/dm³ to mol/dm³?

  Divide by the molar mass in grams
• How do you convert concentration from mol/dm³ to g/dm³?

  Multiply by the molar mass in grams
• What is the method for carrying out an accurate acid-alkali titration?

  1. Add acid to burette using a funnel and record the starting volume.

  2. Add a known volume of alkali to a conical flask and add some indicator.

  3. Place the conical flask on a white tile to see the color change clearly.

  4. Add acid to alkali until reaching the end point.

  5. Calculate how much acid has been added (titre).

  6. Repeat until you get concordant titres.
• What do you know about the volume of acid that reacts with the volume of alkali in a titration?

  You know the exact volume of acid that reacts with the exact volume of alkali
• How do you calculate the concentration of an alkali after a titration?


  Calculate moles of acid, use the mole ratio, and then calculate the concentration of the alkali
• What is the formula to calculate percentage yield of a reaction?

  Percentage yield = (Amount of product produced / Maximum amount of product possible) x 100
• What is the term used for the amount of product obtained from a reaction?

  Yield
• Why is the actual yield of a reaction usually less than the theoretical yield?

  Due to incomplete reactions, practical losses, and side reactions
• What are the causes of actual yield being less than theoretical yield?

  • Incomplete reactions (not all reactants have reacted)
  • Practical losses during the experiment (some product left in the weighing boat)
  • Side reactions (some products react to form other products)
• What is atom economy?

  A measure of the amount of starting materials that end up as useful products
• Why is high atom economy important?

  It is important for sustainable development and economic reasons
• How do you calculate atom economy?

  Atom economy = (Mr of desired product from reaction / Sum of Mr of all reactants) x 100
• What factors should be considered when choosing a reaction pathway to produce a specified product?

  • High atom economy
  • High yield
  • Fast rate
  • Equilibrium position towards products
  • Usefulness of by-products