ok. so my proj is the effect of diiferent solutes on the temperature of boiling water
i chose six solutes.
and my hypotheisis is that salt will cause the maximum rise in the temperature. and sugar will cause the lowest
i went by intution and my teacher says i shld hv reasons to support my hypothesis.
wat should be my hypothesis
2007-07-06 19:15:15 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
The change in BP and FP is related to how much salt is added to the solvent: delta T (change in T) = Km where K is either what's called the molal freezing-point depression constant or molal boiling-point elevation constant; m is the molality of the solution defined as moles of solute (salt) / kilograms of solvent. By knowing the constant for the solvent, how much solvent you have and how much solute you add, you can predict by how much (in degrees C) the BP or FP will change.
The increase in boiling point depends on the number of molecules you add to the liquid. Now salt is a very small molecule. In addition it splits into two particles when in water, the sodium atom and the chloride atom. In numbers: if you add 6g of salt into water you add about 4,400,000,000,000,000,000,000 (4.4 * 10^22) particles to the water.
Sugar has a molecular weight that is 3 times larger than that of salt. It does not split up in different particles when in water. So adding 6 g sugar into water you add around 700,000,000,000,000,000,000 particles (7.3 * 10^21) to the water. Still a huge number, but considerably less than with salt. To get the same effect with sugar that you get with salt, you will have to use about 6 times as much sugar as salt.
The same is true in principle with lowering the freezing point of liquids. That is the reason why we use salt in winter on our streets and not sugar - as we would need 6 times as much for the same effect. But it would work with sugar too, if you use enough of it.
2007-07-07 06:34:30 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The more particles per unit formula of solute, the higher the boiling point will go.
Covalent molecules give one particle. Ionic solutes give two or more, depending on the formula.
2007-07-07 03:20:49 · answer #2 · answered by Gervald F 7 · 0⤊ 0⤋