help me plz!?
2015-10-08 6:08 am
a compound with molecular mass of 88 g is found to contain carbon , hydrogen and oxygen on combustion. 5.17 mg of this compound gives 10.32 mg of carbon dioxide and 4.32 mg of water.Determine the molecular formula of this compound.(given:atomic masses of carbon = 12g , hydrogen = 1 g and oxygen = 16g)
回答 (2)
2015-10-08 6:33 am
10.32 X 12/44 = 2.815 mg C ---- / 12 = 0.235 mmole C
4.32 X 2/18 = 0.48 mg H ---- / 1 = 0.48 mmole H
5.17 - 0.48 - 2.815 = 1.875 g O ---- / 16 = 0.1171875 mmole O
.... divide by smallest
0.235 mmole C / 0.1171875 = 2.005 ~ 2
0.48 mmole H / 0.1171875 = 4.096 ~ 4
0.1171875 mmole O / 0.1171875 = 1
Emp. Formula --- C2H4O ... mass = 44
88/44 = 2
2X (C2H4O) = C4H8O2 <<< molecular formula
4.32 X 2/18 = 0.48 mg H ---- / 1 = 0.48 mmole H
5.17 - 0.48 - 2.815 = 1.875 g O ---- / 16 = 0.1171875 mmole O
.... divide by smallest
0.235 mmole C / 0.1171875 = 2.005 ~ 2
0.48 mmole H / 0.1171875 = 4.096 ~ 4
0.1171875 mmole O / 0.1171875 = 1
Emp. Formula --- C2H4O ... mass = 44
88/44 = 2
2X (C2H4O) = C4H8O2 <<< molecular formula
2015-10-08 6:30 am
[There is no reason to using atomic masses with fewer significant digits than the other given data.]
(10.32 mg CO2) / (44.00964 g CO2/mol) x (1 mol C / 1 mol CO2) x (12.01078 g C/mol) = 2.81646 mg C
(4.32 mg H2O) / (18.01532 g H2O/mol) x (2 mol H / 1 mol H2O) x (1.007947 g H/mol) = 0.48340 mg H
(5.17 mg total) - (2.81646 mg C) - (0.48340 mg H) = 1.87014 mg O
(88 g/mol) x (2.81646 mg C) / (5.17 mg) / (12.01078 g C/mol) = 3.99
(88 g/mol) x (0.48340 mg H) / (5.17 mg) / (1.007947 g H/mol) = 8.16
(88 g/mol) x (1.87014 mg O) / (5.17 mg) / (15.99943 g O/mol) = 1.99
Round to the nearest whole numbers to find the molecular formula:
C4H8O2
(10.32 mg CO2) / (44.00964 g CO2/mol) x (1 mol C / 1 mol CO2) x (12.01078 g C/mol) = 2.81646 mg C
(4.32 mg H2O) / (18.01532 g H2O/mol) x (2 mol H / 1 mol H2O) x (1.007947 g H/mol) = 0.48340 mg H
(5.17 mg total) - (2.81646 mg C) - (0.48340 mg H) = 1.87014 mg O
(88 g/mol) x (2.81646 mg C) / (5.17 mg) / (12.01078 g C/mol) = 3.99
(88 g/mol) x (0.48340 mg H) / (5.17 mg) / (1.007947 g H/mol) = 8.16
(88 g/mol) x (1.87014 mg O) / (5.17 mg) / (15.99943 g O/mol) = 1.99
Round to the nearest whole numbers to find the molecular formula:
C4H8O2
收錄日期: 2021-04-18 00:23:48
原文連結 [永久失效]:
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