For a lab, I have to find the experimental values of i (Van T'Hoff factor).
so far this is what i have, but it's incorrect. could you please tell me what i'm doing wrong??? thanks.
given info:
the lab varied the concentration of Mg(NO3)2
the theoretical value of i is 3
the kg of water is .05129 kg
the delta T is 1.9 (101.9-100)
the g of Mg(NO3)2 is 9.20 g
i = kb*g*deltaTb/GMW*kg of solvent
i = (.515 degreesCkg/mol*9.20g*1.9 degrees C)/(210.33g)(.05129)
i=10?!?!?! ...i stopped bc ten is wayyy off.
For starters I found the molar mass Mg(NO3)2 to be 148.149. Did you use a hydrated form of Mg(NO3)2 or did you just add the numbers wrong.
Second, I find with these equations that it is too easy to make a math error with all the slashes for divisions, especially in the denominator. If I use your numbers (with the 210.33 for the molar mass) I found 4.32. Using my value of 148.15 I found 3.047. I think you would be well advised to do the problem piece-meal. Like so.
Delta T = 1.9 as you have.
mols Mg(NO3)2 = 9.2/148.15 = 0.06210
m = mols/kg = 0.06210/0.05129 = 1.2108
i = delta T/(Kb*m) = 1.9/(0.515*1.2108) = 3.047. You may not be allowed that many significant figures but you can check your work with my readings. Check my work. Check my thinking.
[Putting it all together, I find the final equation to be like this but check me out.
i = (delta T*kg solvent*GMW)/(Kb*grams solute) = 3.047.
thank you so much! the molar mass was a major problem...i didn't realize i was so off. thank you for pointing that out.
To find the experimental value of i (Van T'Hoff factor), you are using the correct formula, but there seem to be a few errors in your calculations. Let's go through the calculations step by step to identify and correct the mistakes.
First, let's break down the formula:
i = θb * g * ΔTb / (MW * kg of solvent)
θb represents the van't Hoff factor for the solute, g is the mass of the solute in grams, ΔTb is the change in boiling point in degrees Celsius, MW is the molar mass of the solute, and kg of solvent represents the mass of the solvent in kilograms.
Now let's go through the values provided and perform the calculations:
θb (theoretical value) = 3
g = 9.20 g
ΔTb = 1.9 °C
MW of Mg(NO3)2 = 148.3 g/mol
kg of water (solvent) = 0.05129 kg
i = (θb * g * ΔTb) / (MW * kg of solvent)
= (3 * 9.20 * 1.9) / (148.3 * 0.05129)
Now, let's calculate it step by step:
i = (3 * 9.20 * 1.9) / (148.3 * 0.05129)
= 52.56 / 7.6197
= 6.89 (rounded to two decimal places)
Therefore, the experimental value of i is approximately 6.89, which is different from the theoretical value of 3. This suggests that there could be factors influencing the observed behavior of the solute that deviate from the expected theoretical value.
Make sure to double-check your calculations and use the correct values in your formula to get an accurate result.