4. A scientist is investigating the properties of a mixture of CH3OH and H2CO. The scientist generat — Hybridization, Intermolecular Forces, Phase Changes, Thermodynamics Chemistry Question
Problem Context
- A scientist is investigating the properties of a mixture of CH3OH and H2CO. The scientist generates the following diagram to represent the mixture.
A. Identify the hybridization of the valence orbitals of the C atom in the H2CO molecule.
Model Answer
sp² (extracted from the rubric as *2sp* due to formatting) [1].
B. In the diagram provided, draw a SINGLE dashed line (----) to represent a strong hydrogen-bonding attraction between one CH3OH molecule and one H2CO molecule in the mixture.
Model Answer
The diagram should show a dashed line between the O atom in one H₂CO
molecule and the H atom in the OH group of one CH₃OH molecule [1].
C. The scientist plans to cool a gaseous mixture of CH3OH and H2CO to form a liquid mixture and finds data on the two compounds. The data are summarized in the table.
i. Propose a temperature to which the mixture should be cooled such that CH3OH and H2CO will both be liquids.
Model Answer
The proposed temperature should be in the range 181 K−254 K [2].
ii. The scientist analyzes the mixture after it is cooled and determines that 8.59 g of CH3OH(l) is present. Calculate the amount of thermal energy, in kJ, that was removed to condense the 8.59 g of CH3OH (molar mass 32.04 g/mol) at its boiling point.
Model Answer
8.59 g CH₃OH × (1 mol CH₃OH / 32.04 g CH₃OH) × (-37.6 kJ / 1 mol
CH₃OH) = -10.1 kJ, so 10.1 kJ are removed [2].
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