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Can you determine the empirical formulas for the following compounds (showing the...

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lkehoe | Valedictorian

Posted November 1, 2013 at 10:52 PM via web

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Can you determine the empirical formulas for the following compounds (showing the work)?

2.  A 6.21 gram sample of a compound contains 4.54 grams of iodine and the rest is cerium.

3.  The compound benzoic acid contains 68.8% carbon, 4.95% hydrogen, and 26.2% oxygen by mass.

4.  Freons are gaseous compounds used in refrigeration.  One particular Freon contains 9.93% carbon, 58.6% chlorine, and 31.4% fluorine by mass.

5.  A germicidal compound is found to be 33% sodium, 36% arsenic, and 31% oxygen.  What is the formula of this compound?  What is this compounds name?

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted November 2, 2013 at 4:16 AM (Answer #1)

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The compound is made up of iodine and cerium. A 6.21 gram sample of the compound contains 4.54 grams of iodine and 1.67 grams. The molar mass of iodine is 126.9 g/mole and the molar mass of cerium is 140.1 g/mole

1.67 g of cerium is equivalent to 0.012 moles and 4.54 g of iodine is equivalent to 0.036 moles. For each mole of cerium, the compound has 3 moles of iodine.

This gives the empirical formula of the compound as `CeI_3`

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lkehoe | Valedictorian

Posted November 6, 2013 at 7:43 PM (Reply #1)

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Can you show your work on this problem?

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Yojana_Thapa | TA , Grade 10 | Valedictorian

Posted January 25, 2014 at 7:06 PM (Answer #2)

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2.  A 6.21 gram sample of a compound contains 4.54 grams of iodine and the rest is cerium.

  • Iodine: 4.54g

     Atomic Mass: 127

    # of moles of element: (4.54/127)= 0.035

    Simplest ratio of moles: (0.035/0.011)= 3

  • Cerium: 1.67g

    Atomic Mass: 140

    # of moles of element: (1.67/140)= 0.011

    Simplest ratio of moles: (0.011/0.011) = 1

Empirical Formula = I3Ce

3.  The compound benzoic acid contains 68.8% carbon, 4.95% hydrogen, and 26.2% oxygen by mass.

  • Carbon: 68.8%

    Atomic Mass: 12

    # of moles of element: (68.8/12)= 6

    Simplest ratio of moles: (6/2) = (3 x 2) = 6

  • Hydrogen: 4.95%

    Atomic Mass: 1

    # of moles of element: (4.95/1)= 5

    Simplest ratio of moles: (5/2) = (2.5 x 2) = 5

  • Oxygen: 26.2%

    Atomic Mass: 16

    # of moles of element: (26.2/16)= 2

    Simplest ratio of moles: (2/2) = (1 x 2) = 2

Empirical Formula = C6H5O2

5.  A germicidal compound is found to be 33% sodium, 36% arsenic, and 31% oxygen.  What is the formula of this compound?  What is this compounds name?

  • Sodium: 33%

    Atomic Mass: 23

    # of moles of element: (33/23)= 1.434

    Simplest ratio of moles: (1.434/0.48) = 3

  • Arsenic: 36%

    Atomic Mass: 75

    # of moles of element: (36/75)= 0.48

    Simplest ratio of moles: (0.48/0.48) = 1

  • Oxygen: 31%

    Atomic Mass: 16

    # of moles of element: (31/16)= 1.937

    Simplest ratio of moles: (1.937/0.48) = 4

Empirical Formula = Na3ASO4 (Sodium Arsenate)

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parama9000 | TA , Grade 11 | Valedictorian

Posted January 30, 2014 at 7:27 AM (Answer #3)

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CeI3

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parama9000 | TA , Grade 11 | Valedictorian

Posted January 30, 2014 at 7:32 AM (Answer #4)

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C6H502

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