ned help answering these I keep getting them wrong 3/18/2018 11:00 PM 0 85.2/100

Question

ned help answering these I keep getting them wrong

3/18/2018 11:00 PM 0 85.2/1003/13/2018 04:01 PM Print Calculator Periodic Table uestion 10 of 24 Sapling Learning macmillan learning A sample of C3H8 has 3.44 x 1024 H atoms. How many carbon atoms does the sample contain? Number 1.29 x 104 C atoms What is the total mass of the sample? Number 18.92 x 1024 g C, H There is a hint availablel ew the hint by clicking on the divider bar again to hide the hint. Close botiom divider on the O Previous Give Up search

Explanation / Answer

1) A sample of C3H8

mass Hydrogen = 3.44 x 10^24 atoms

moles Hydrogen = 3.44 x 10^24 atoms/6.023 x 10^23 = 5.711 moles

in the molecule we have,

3 moles C to every 8 moles Hydrogen

So,

moles Carbon = 5.711 moles x 3/8 = 2.142 moles

mass of Carbon in sample = 2.142 moles x 6.023 x 10^23 = 1.30 x 10^24

Total mass = 2.142 moles x 12 g/mol + 5.711 moles x 1 g/mol = 31.415 g

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2) moles C = 15.8 g/44 g/mol = 0.36 moles

mass C = 0.36 moles x 12 g/mol = 4.31 g

moles H = 2 x 6.46 g/18 g/mol = 0.72 moles

mass H = 0.72 moles x 1 g/mol = 0.72 g

Mass O = 7.90 - (4.31 + 0.72) = 2.87 g

moles O = 2.87 g/16 g/mol = 0.18 moles

divide by smallest factor,

C = 0.36/0.18 = 2

H = 0.72/0.18 = 4

O = 0.18/0.18 = 1

So empirical formula becomes = C2H4O

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3) First dilution,

50 ml of 1.60 M solution diluted to 288 ml

final concentration = 1.60 M x 50 ml/288 ml = 0.28 M

Second dilution,

144 ml of 0.28 M solution diluted by adding 153 ml water

Total final volume = 144 + 153 = 297 ml

Final concentration = 0.28 M x 144 ml/297 ml = 0.136 M

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