emtahanat

• Stable Ion with a two plus charge


  An element which is in group two of the periodic table
• The least reactive element in period 3 is a noble gas, which is argon
• Chlorine is used in water treatment to kill microorganisms
• The main impurity in iron ore is silicon
• Calcium carbonate is added to react with the silicon dioxide impurity to form slag
• Phosphorus is an important component in fertilizers
• Group 1 metals are stored under oil to prevent reaction with water
• Aluminum is used in food containers because it is light and good at keeping air out
• Sulfur is found in zinc blende
• Reaction of calcium with water to form calcium hydroxide

  Calcium + Water → Calcium Hydroxide + Hydrogen
• Calcium oxide also reacts with water to form calcium hydroxide
• Weakly alkaline


  pH between 8 and 10
• The ion responsible for making the solution alkaline is OH-
• Lime water is used to test for carbon dioxide
• Making a sample of lime water


  Add excess solid calcium hydroxide to water and filter out the excess
• The reason for adding excess solid calcium hydroxide is to ensure a saturated solution
• Testing for calcium ions in lime water

  Add aqueous sodium hydroxide, which will displace the calcium to form a white precipitate of calcium hydroxide
• Buret


  The apparatus used to measure the volume of acid in a titration
• Neutralization


  The type of reaction that takes place in the titration
• An indicator must be added to the conical flask to determine when the solution is neutralized
• Determining the concentration of calcium hydroxide in lime water

  Calculate the moles of HCl in 20 cm3 of 0.05 M HCl

  2. Determine the moles of calcium hydroxide in 25 cm3 of lime water using the reaction equation

  3. Calculate the concentration of calcium hydroxide in mol/dm3

  4. Convert the concentration to g/dm3 using the molar mass of calcium hydroxide
• Isotopes


  Atoms of the same element with the same proton number but different neutron number
• Manganese has only one isotope
• The nuclear number (mass number) of manganese is 55
• Determining the number of protons, neutrons and electrons in the chromium(III) ion

  The proton number is 24

  2. The number of neutrons is 28 (mass number 52 - proton number 24)

  3. The number of electrons is 21 (proton number 24 - charge of 3+)
• Transition elements


  • Form colored compounds

  2. Can act as catalysts

  3. Have variable oxidation states
• Hydrated copper sulfate is blue, hydrated cobalt chloride is pink
• Electrical conductivity of transition and group 1 metals

  Due to the presence of free moving, delocalized electrons
• Copper sulfate


  When hydrated, it will be blue
• Cobalt chloride


  When hydrated, it will be pink
• Chemical properties of transition elements

  • Can act as a catalyst
  • Have variable oxidation states
• Transition elements and group 1 elements are metals
• Conducting electricity


  Requires free moving ions or electrons
• Transition elements and group 1 elements conduct electricity because they have free moving, mobile electrons</b>
• Malleable


  Describes a material which can be hammered into shape
• Ductile


  Describes a material which can be made into wires
• Physical properties of transition elements compared to group 1 elements

  • Higher density
  • Higher melting points
• Fluorine

  Pale yellow gas
• Determining molecular formula


  1. Calculate mass of sulfur

  2. Calculate mass of fluorine

  3. Divide masses by respective atomic masses to get number of atoms

  4. Molecular formula is S2F10
• LiCl is a solid at room temperature


  Due to strong ionic bonding