Give the intermolecular force that is responsible for the solubility of ethanol

Question

Give the intermolecular force that is responsible for the solubility of ethanol in water. dispersion forces dipole-dipole forces hydrogen bonding ion-dipole forces ionic forces Answer: _____ Which of the following ions should have the most exothermic Dleta H hydration? Na^+ Mg^2+ Al^3+ Ca^2+ Sr^2+ Answer:_____ Determine Delta H_lattice for KBr if the Delta H_solution (KBr) = +19.9 kJ/mol and the Delta H_hydration (KBr) = -670. kJ/mol. +650 kJ/mol -650 kJ/mol +690 kJ/mol -710 kJ/mol -690 kJ/mol Answer:_____ A solution is formed at room temperature by vigorously dissolving enough of the solid solute so that some solid remains at the bottom of the solution. Which statement below is true? The solution is considered unsaturated. The solution is considered supersaturated. The solution is considered saturated. The solution would be considered unsaturated if it were cooled a bit to increase the solubility of the solid. None of the above are true. Answer:____

Explanation / Answer

1) The solubility of ethanol in water is due to H- bonding. BOth of them have H- bonds in them, thus can form H-bond betwen them, making them miscible.

2) HYdration is more for smaller cations with higher charge.

Al+3 is the ion with small size and highest charge among the given species.

Thus Al+3 ion is the most hydrated ion, thus has highest enthalpy of hydration.

3) We know enthalpy of solution = enthalpy of hydration + lattice enthalpy

Thus +19.9 kJ = -670kJ + lattice enthalpy

Therefore lattice enthalpy = 19.9 + 670 = 689.9 kJ

The sign of lattice enthalpy here is +ve because during dissolution , it is the energy suppled.

However , the actual lattice enthalpy is defined as the amount of energy liberated when one mole of ionic crystalline solid is formed from the constituent ions. Thus it must be reported with negativ esign.

There fore the delta H lattice = -689.9 kJ/ mol rounded up as -690kJ/mol

5) A solution with some solute remaining undissolved at room temperature is a saturated solution.

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