chem test 2

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chem test 2
2010-05-12 15:18:06
chem test

chem test 2
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  1. HW 18: RQ CH 16
    1. What defines a material as being a mixture?
    A material is a mixture if the substanes making up the mixture retain their own properties.
  2. HW 18/CH 16
    RQ 2
    How can the components of a mixture be separated from one another?
    Components of a mixture can be separated by physical means. One method is filtration, another is distillation.
  3. HW 18 CH 16 RQ 3
    How does distillation separate the components of a mixture?
    Distillation separates the components by using the different boiling points or components. The component that boils at a lower temperature is vaporized and is collected by exposing it to cooler temperatures over a receiving flask which collects the condensed purified liquid.
  4. HW 18 CH 16 RQ5
    How is a solution different from a suspension?
    A solution is a homogeneous mixture in which all components are in the same phase. A suspension is a homogeneous mixture in which the various components are in different phases.
  5. hw 18, ch 16, rq 8
    Why is ruby considered a solution?
    Ruby is a solid solution of trace quantities of red chromium compounds in transparent aluminum oxide. The solution is homogeneous and both components are in the solid phase.
  6. hw 18, ch 16, rq 9
    Distinguish between a solute and a solvent.
    A solvent is the component in a solution that is present in the largest amount. A solute is any component in a solution that is not the solvent.
  7. hw 18, ch 16, rq 11
    One mole of particles is a very large number of particles or a very small number?
    • One mole is a very large number of particles.
    • 1 mole = 602,000,000,000,000,000,000,000,000 particles.
  8. hw 18, ch 16 ex 1
    Classify each of the following as a homogeneous mixture, a heterogeneous, an element, or a compound.
    milk - homogeneous mixture; steel - homogeneous mixture; ocean water - heterogeneous mixture; blood - homogeneous mixture; sodium - element
  9. P 4
    Show that 45 gm of sodium chloride is needd to make 15 L of a solution than concentration of 3.0 gm of sodium chloride per liter of solution.
    • Concentration= Mass of solution
    • ______________
    • volume of solvent = 3.0 gm/L

    • molarity = 2 moles of NaCl
    • ---------------------
    • .5 L of water = 4 M
  10. 11.
    If you had 2 moles of pennies, how many pennies would you have?
    • 1 mole = 602,000,000,000,000,000,000,000 pennies
    • 2 moles= 1,204,000,000,000
  11. What is the purpose of coefficients in a chemical equation?
    The coefficients tell exactly the quantities of the reactants and products.
  12. How many chromium atoms and how many oxygen atoms are indicated on the side of this balanced chemical equation?
    4 Cr (s) + 3 )2 (g) -> 2 Cr2O3 (g)
    There are four chromium atoms and six oxygen atoms on the right side.
  13. 3
    What do the letters (s), (l), (g) and (aq) stand for in a chemical equation?
    (s) stands for solids, (l) stands for liquid, (g) stands for gas, and (aq) stands for aqueneous (which is a material dissolved in water).
  14. 4.
    Why is it important that a chemical equation be balanced?
    Chemical equations have to be balanced due to the nature of conservation of mass. You have to have the same number of atoms on each side of the equation.
  15. 8.
    What is the mass of a single sodium atom in atomic mass units?
    22,990 amu
  16. 9
    What is the formula mass of nitrogen monoxid, NO, in atomic mass units?
    30,006 amu
  17. 11
    If you had 2 moles of pennies, how many pennies would you have?
    • 1 mole = 602,000,000,000,000,000,000,000
    • 2 moles = 1,204,000,000,000,000,000,000,000
  18. 12
    How many moles of water are there in 18 gm of water?
    There is one mole of water in 18 gm of water.
  19. 13
    How many molecules of water are there in 18 gm of water?
    602,000,000,000,000,000,000,000 water molecules
  20. 21
    What does a catalyst do to the energy barrier of a reaction?
    The catalyst lowers the energy barrier of a reaction.
  21. 24
    If it takes 436 kJ to break a bond, how many kilogoules are released when the same bond is formed
    436 kJ, because it takes the same to break the bond as to form the bond.
  22. 26
    What is released by an exothermic reaction?
    Energy is released in an exothermic reaction.