Answer:
Molecular formula A: C₅H₁₀
Molecular formula B: C₇H₁₄
Explanation:
It is possible to obtain empirical formula of compounds using percent composition, thus:
C: 85.7% × (1mol / 12.01g) = 7.136 moles C
H: 14.3% × (1mol / 1.01g) = 14.158 moles H
Mole ratio of H:C is:
14.158mol / 7.136mol = 2
That means in compounds A and B you have 2 hydrogens per atom of carbon and empirical formila is:
CH₂
Using PV = nRT, moles of A and B are:
<em>Where P is pressure (750mmHg / 760 = 0.987atm), V is volume (0.8000L), R is gas constant (0.082atmL/molK), and T is temperature (150°C +273.15 = 423.15K)</em>
Moles A and B: n = PV / RT
n = 0.987atm×0.8000L / 0.082atmL/molK×423.15K
n = 0.0228 moles of A and B.
Using the mass of A and B it is possible to find molar mass of each compound:
A = 1.60g / 0.0228mol = 70.31g/mol
B = 2.22g / 0.0228mol = 97.56g/mol
As empirical formula of both compounds is CH₂, (molar mass = 14.03g/mol). Molecular formula of compounds is:
A = 70.31g/mol / 14.03g/mol = 5 → Molecular formula: 5×CH₂ = <em>C₅H₁₀</em>
B = 97.56g/mol / 14.03g/mol = 7 → Molecular formula: 7×CH₂ = <em>C₇H₁₄</em>
