chemistry test

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bridgit
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29371
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chemistry test
Updated:
2010-08-17 03:04:32
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chemistry
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to help me study for the chemistry test on chapters 10,11 and 12
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  1. What are the physical properties that make water unique?
    • Boiling point: 100ºC
    • Frezzing point: 0ºC
    • Heat capacity: 4.2Jg-1ºC-1 (4.2 joules of energy is required to heat up one gram of water by one degree)
    • Solubility: ability to dissolve other substances
  2. What happen to water when it is frozen?
    • It expands
    • It becomes less dense, this is due to the alignment of every hydrogen atom with oxygen atoms. This means there is space created inbetwen H2O molecules.
  3. How much energy is required to heat up one gram of water by one degree?
    • 4.2 joules
    • 4.2Jg-1ºC-1
  4. What happens to soluble substances when placed in water?
    Water molecules pull other molecules apart if they are polar and are attracted. Then the water molecules surround the atom and it 'disapears'.
  5. How much enery i required to heat one gram of the following substances to one degree (water, ethanol, iron, lead, copper and sand)
    • Water: 4.2
    • Ethanol: 2.4
    • Iron: 0.45
    • Lead: 0.13
    • Copper: 0.39
    • Sand 0.48
  6. remember
  7. What units are used in concentration?
    • g/100g
    • g/litre
    • M/moles/litre
  8. What concentration equration do you use if moles stay the same?
    C1V1=C2V2 for dilution
  9. What is crystallisation?
    Solutions that are no longer soluble form a crystalisation this could be due to temperature change.
  10. What is supersaturation?
    It is a solution that contains more dissolved solutes than a saturated soultion. Any point above the solubility curve.
  11. What is a precipitation reaction?
    When two solutions are mixed and a solid id formed
  12. What is an ionic equation?
    An equation were the spectator ion are omitted
  13. What is flocculation?
    It is the process by which small particles suspended in the water join together to form larger heavier particles the sink to the bottom. This is achieved by adding aluminium sulfate and sometimes lime (to neutralise acids and provide a source of hydroxide ions).
  14. What in addition can be added for the process of flocculation?
    • Lime
    • Ca(OH)2(s)--->Ca(aq)+2OH(aq)
  15. What is added to achieve flocculation and what does it do?
    • Aluminium sulfate
    • Al(aq)+3OH(aq)--->Al(OH)3(s)
    • Aluminium hydroxide is produced in the form of gelatinous precipitate called floc, which traps other fine particles and removes color and some microorganiams from the water.
  16. What is settling?
    When the water is left to stand leting the floc settle to form sluge.
  17. What is filtering?
    Water from the settling tank is allowed to filter down through a bed of sand over gravel. This removes any suspended matter.
  18. What is chlorination?
    • After filtering, the clean water is usually treated with gaseous chlorine to destroy bacteria. Chlorine reacts with water.
    • Cl2(g)+H2O(l)--->HOCl(aq)+H(aq)+Cl(aq)
  19. What is hard water?
    Where more soap need to be used to produce a lather. It i caused by the presence of some metal ions, mainly calcium, magnesium and iron.
  20. What is desalination?
    The process of removeing salts from sea water in order to produce fresh water. There are three ways of doing this, though distillation, reverse osmosis and ion exchange.
  21. What are substances that dissolve readily in water?
    • Polar covalent compunds that can form hydrogen bonds with water
    • Polar covalent molecular compounds that ionise
    • Ionic compounds
  22. What is a polar covalent compound that can form hydrogen bonds with water?
    • hydrogen bonds between water molecules are broken
    • hydrogen bonds between eg ethanol molecules are broken
    • hydrogen bonds between water molecules and ethanol molecules are formed
  23. What are covalent molecular compunds tgat ionise?
    • polar covalent bonds within molecules are broken, production hydrogen ions and anions
    • a covalent bond forms between each H+ and an H2O molecule, giving H3O+ ions. Ion-dipole attractions between the newly formed ions and the pola water molecules are formed.
  24. How do ionic componds dissolve?
    • ionic bonds within the soild are broken
    • hydrogen bonds between water molecules are broken
    • ion-dipole attractions between the ions and the polar water molecules are formed
  25. How do you covert metric units of volume?
    millilitre÷10^3=litre
  26. calculate the amount of moles in a solution
    n=C*V
  27. Calculate the molar concentration in a soulution.
    c=n/v
  28. Calculate the amount of moles
    n=m/M

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