Need help with dat acheiver question

[Dr rice]

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It would be sweet if someone could explain to me how number 59 of the second dat acheiver test works. I looked at the explaination for about 30 minutes and I can't figure it out. I have also noticed a lot of spelling and math errors in DAT acheiver. Has anyone else noticed this. The question deals with molality of 85% compound.
thanks

 

[pbure9]

Hey man. This one was ******ed.

The answer is B and if you look closely, the cancel out all the BS you don't need in this question, like the density.

This is how I solved it, then was like wtf when i saw the choices.

85% of H3PO4 is 85g H3PO4 in 15g of H2O and you need molality, so we need moles H3PO4 and kg H2O.... so:

85g H3PO4/15g H2O x (1000g/1kg) x (1 mole H3PO4/98g H3PO4) which if you cut through all the crap is B.

And while we're at it, did you understand number 68? How does H2O expand when it freezes? 😵

 

[g23armani]

Water is somewhat unique in that it has a lower density in solid form than in liquid form. This is why ice floats.

 

[pbure9]

Water is somewhat unique in that it has a lower density in solid form than in liquid form. This is why ice floats.

meaning that it expands upon freezing?

 

[g23armani]

Yes. Density is mass over volume. So with a given mass of water it will expand when it freezes, lowering the density.