taramgrant0543664
  • taramgrant0543664
So I've seen a bunch of these questions recently so I put together a simple step by step example for freezing point depression let me know what you think!!
Chemistry
  • Stacey Warren - Expert brainly.com
Hey! We 've verified this expert answer for you, click below to unlock the details :)
SOLVED
At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
chestercat
  • chestercat
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
taramgrant0543664
  • taramgrant0543664
Question: 31.65 g of sodium chloride is added to 220.0 mL of water at 34 °C. How will this affect the freezing point of the water? Assume the sodium chloride completely dissociates in the water. Given: density of water at 35 °C = 0.994 g/mL Kf water = 1.86 °C kg/mol
taramgrant0543664
  • taramgrant0543664
Solution: To find the temperature change elevation of a solvent by a solute, use the equation: ΔT = iKfm where ΔT = Change in temperature in °C i = van 't Hoff dissociation factor Kf = molal freezing point depression constant or cryoscopic constant in °C kg/mol m = molality of the solute in mol solute/kg solvent.
taramgrant0543664
  • taramgrant0543664
Step 1: Calculate the molality of the NaCl molality (m) of NaCl = moles of NaCl/kg water From the periodic table atomic mass Na = 22.99 atomic mass Cl = 35.45 moles of NaCl = 31.65 g x 1 mol/(22.99 + 35.45) moles of NaCl = 31.65 g x 1 mol/58.44 g moles of NaCl = 0.542 mol kg water = density x volume kg water = 0.994 g/mL x 220 mL x 1 kg/1000 g kg water = 0.219 kg mNaCl = moles of NaCl/kg water mNaCl = 0.542 mol/0.219 kg mNaCl = 2.477 mol/kg

Looking for something else?

Not the answer you are looking for? Search for more explanations.

More answers

taramgrant0543664
  • taramgrant0543664
Step 2: Determine the van 't Hoff factor The van 't Hoff factor, i, is a constant associated with the amount of dissociation of the solute in the solvent. For substances which do not dissociate in water, such as sugar, i = 1. For solutes that completely dissociate into two ions, i = 2. For this example NaCl completely dissociates into the two ions, Na+ and Cl-. Another example could be CaCl2 which dissociates into three ions, Ca2+ and 2Cl-. But, i = 2 for this example.
taramgrant0543664
  • taramgrant0543664
Step 3: Find ΔT ΔT = iKfm ΔT = 2 x 1.86 °C kg/mol x 2.477 mol/kg ΔT = 9.21 °C
taramgrant0543664
  • taramgrant0543664
So the final answer is: Adding 31.65 g of NaCl to 220.0 mL of water will lower the freezing point by 9.21 °C.
taramgrant0543664
  • taramgrant0543664
The normal freezing point of water is 0°C with the addition of NaCl the freezing point for this solution would be -9.21 °C.
Photon336
  • Photon336
nice job tara
arindameducationusc
  • arindameducationusc
Nice one... @taramgrant0543664
Photon336
  • Photon336
one other thing: remember that delta T is the temperature change not the final temperature that the substance was raised or lowered to. so if they ask for the final temperature you'll need to do some rearranging: \[\Delta T = (Tf-Ti) \] to get \[\Delta T + Ti = Tf \]
Zale101
  • Zale101
Awesome work @taramgrant0543664
taramgrant0543664
  • taramgrant0543664
Thanks everyone! And yes @Photon336 thanks for pointing that out!
Photon336
  • Photon336
There should be a way for us to find these tutorials in the future though
taramgrant0543664
  • taramgrant0543664
There's one of the mods that runs a tutorial site thing on behalf of openstudy or in conjunction with or something along the lines I know that I can't remember which one it is though
Photon336
  • Photon336
@taramgrant0543664 do you know that mod's name? ah.. okay
Photon336
  • Photon336
ok.. thanks
shreehari499
  • shreehari499
Good one @taramgrant0543664 ... And yeah I've given a tutorial on genetics 2 days back as well.. Please check it out..:)
taramgrant0543664
  • taramgrant0543664
You did @shabbaranks genetics is my favourite bio course! I must have missed it normally I don't miss too much but ill definitely check it out!
Photon336
  • Photon336
after a while you cant bump up the tutorial to the top; i'm guessing you can just paste the link to your profile description?
anonymous
  • anonymous
good job :)
Ciarán95
  • Ciarán95
Brilliant work @taramgrant0543664 ! :D

Looking for something else?

Not the answer you are looking for? Search for more explanations.