Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Molthisok on August 27, 2020, 10:43:53 AM
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.10 mol NaF
.10 mol IF_3
.10 mol HF
My best guess was IF_3 because it had the largest molar mass, but my professor’s key says I’m wrong
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Why do you consider IF3 to be a stable ionic compound in the water? You will never get an aqueous solution of this compound - it decomposes completely at -28°C.
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The answer could depend on what are the the IF3 decomposition products. However, there is definitely an error in your reasoning, as
because it had the largest molar mass
molar mass doesn't matter here at all.
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The chemistry of interhalogen compounds is very far from general chemistry.
IF3 at -28°C disproportionates to form iodine and iodine pentafluoride. IF5 is fairly stable but reacts vigorously with water to form iodic acid (HIO3) and hydrofluoric acid (this reaction can be found in Wikipedia).
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If we ignore the IF3 decomposition, we could say:
NaF is an ionic compound with full water solubility. Each mole of NaF creates one mole of F- in water.
HF is a weak acid, so 1 mole of HF will dissociate partially to create less than one mole of HF is water.
IF3 is a covalent compound, so it will not dissociate in water at all, making zero moles of F- in water.
The molar mass does not matter because have already been given moles as your unit.
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If we ignore the IF3 decomposition, we could say:
IF3 is a covalent compound, so it will not dissociate in water at all, making zero moles of F- in water.
This is chemical nonsense. We will never introduce IF3 into the water, but possibly the equivalent (taking into account fluorine) amount of IF5 that decompose in the water giving 0.3 M HF.
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If we ignore the IF3 decomposition, we could say:
IF3 is a covalent compound, so it will not dissociate in water at all, making zero moles of F- in water.
This is chemical nonsense. We will never introduce IF3 into the water, but possibly the equivalent (taking into account fluorine) amount of IF5 that decompose in the water giving 0.3 M HF.
If the professor is asking a question like this, I assume this is the answer they want. For all we know, the person assigning the question doesn't even know IF3 is unstable. Generally, non-acidic and non-basic covalent compounds do not make ions in water. I assume based on the fact that this is undergraduate general chemistry forum.