DAT Destroyer Gen Chem #87 Help!

[egan]

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Hey guys,

Here's the question:

87. A solution of LiCl has a density of 1.13g/cm3 at 25 degrees C. If the solution is 20% by weight LiCl, which is the molarity?

Answer:
20g LiCl/100g solution x 1.13g solution/1cm3 x 1000cm3/1 liter x
1 mol LiCl/42.5g LiCl

It all makes sense except for the second step if 1.13 is the density of LiCl how can u use that as the density of the solution to get grams LiCl? I think I'm missing something conceptually here but can't figure it out

Let me know what you guys think.

 

[rockclock]

Hey guys,

Here's the question:

87. A solution of LiCl has a density of 1.13g/cm3 at 25 degrees C. If the solution is 20% by weight LiCl, which is the molarity?

Answer:
20g LiCl/100g solution x 1.13g solution/1cm3 x 1000cm3/1 liter x
1 mol LiCl/42.5g LiCl

It all makes sense except for the second step if 1.13 is the density of LiCl how can u use that as the density of the solution to get grams LiCl? I think I'm missing something conceptually here but can't figure it out

Let me know what you guys think.

I think you have your answer

 

[ForeverKhaled]

1.13 is the density of the solution not the LiCl

I had the same problem a while back but this should help you

 

[AllahIsGreater]

1.13 is the density of the solution not the LiCl

I had the same problem a while back but this should help you

its a dimensional analysis problem. the only reason you use the density, is recall 20% means you have 20 grams or LiCl per 100 grams of solution or (20g/100g)

so Molarity = mol / L

so using the actual weight we can get the moles, however to go from 100g of solution to liters of solution, we must use the density as our middleman. i know this is a crappy explanation, but if u want i can email you a paint document explaining the work.