By the way, use 58 as the molar mass of salt. Oh, and the Kf of water is 1.86ºC/m.
Thank you in advance for your help.
2007-03-13 13:23:28 · 3 answers · asked by Random G 3 in Science & Mathematics ➔ Chemistry
I think you mean freezing at -5 degrees C, since the freezing point goes DOWN when you add salt.
delta T = -Kf * m * i
-5 = - 1.86m * (moles of salt)/5 kg * 2
The 2 comes about because for every one mole of NaCl that dissolves in solution, 2 moles of ions are formed.
moles of salt = 6.72 moles NaCl
6.72 moles * 58 g/mol = 390 grams of NaCl
2007-03-13 13:30:12 · answer #1 · answered by ihatedecaf 3 · 0⤊ 0⤋
It will never freeze at 5 C no matter how much salt you add. The freezing point of water is 0 C and salt lowers the freezing point.
2007-03-13 20:27:01 · answer #2 · answered by xox_bass_player_xox 6 · 0⤊ 0⤋
You're going to have to put a lot of pressure on the water to get it to freeze at 5 C. And I do mean a lot.
2007-03-13 20:28:44 · answer #3 · answered by morningfoxnorth 6 · 0⤊ 0⤋