Hello
would this be right ,sorry for asking i wasnt there when my teacher went over this
That's fine.
Also how do you know if the molecule is polar or non polar i am quite confused
So like, people will shy away from this method - mainly because it involves learning something new - but I personally think this is the easiest way to learn polarity. First, you need to learn about vectors and how to add vectors to each other geometrically:
https://www.mathsisfun.com/algebra/vectors.htmlRead this - it's an amazing resource. All you need to understand is:
a) What a vector is (a direction with magnitude)
b) How to add one vector to another (head-to-tail)
If you don't understand the website, just ask - but it should be straightforward. You don't need to understand how subtraction, scalar multiplcation, notation, or how ANYTHING else works. Just how to add vectors together. Got it? Awesome.
If you look at the picture attached, you can actually draw vectors over a pair of atoms. You can think of these vectors as a "force" that the electrons exert when they're more attracted to one atom over the other. (it's slightly more complicated than that, but this intuition is enough to explain polarity on a basic level) You'll notice there's a plus on the not-pointy end - you can use this plus to remember which side is more positive. There are three rules you need to know about these arrows:
- The arrow points towards the more electronegative atom.
- The bigger the difference in electronegativity, the bigger the vector will be.
- The arrows ONLY exist between two atoms - lone pairs don't count.
Using this, how can you tell if a molecule is polar or not? Well, if you draw all of these arrows between each pair of bonding atoms (we call these "dipole vectors"), and add them all up, then the molecule will be NON-POLAR is the arrows return to the starting point, and POLAR if they do not. If you look at my second picture, there's an example for ACl
3 - in this case, since the arrows return to the starting point (in red), the molecule must be non-polar. However - if you were to do this with HCN (this molecule is linear, with a single bond connecting the H to the C and a triple bond to the C and N), then the two dipole vectors would be different sizes, and would point to somewhere that isn't the middle - try it out for yourself!
The only problem with this method, is you need to add the vectors in 3D - so it's harder to do for parent geometries with 4, 5, or 6 electron domains. However, something that is handy to know - in a tetrahedral atom, if all of the dipole vectors are the same size, then the molecule will be non-polar. The same for a trigonal bipyramidal molecule or an octahedral molecule. Hopefully knowing this will make it easier for you to try and imagine what's happening in 3D.
and thank you for your really detailed explanation above!
All good, man!
Hi, could someone please help me with the following?
1. How do we predict half-equations for organic molecules and acid-base reactions in general? I know this is a vague question, but I don't understand how to predict reactions to perform calculations related to volumetric analysis
Half-reactions is something we discuss for redox reactions, not acid-base reactions or typical organic reactions. The general trick is:
a) If it's an acid base reaction, you'll be making a salt + water
b) If it's an organic molecule, you need to understand its reactivity and possible reaction pathways
c) If you have no clue and the question hasn't told you what it should be, assume 1:1 stoichiometry. At the very least, you'll get consequential marks
2. I have no idea what this question is asking me to do and the solutions don't make sense to me:
"The amount of vitamin C in fruit juice can be determined by titration with a standard 0.0100 M iodine solution:
C6H8O6(aq) + I2(aq) → C6H6O6(aq) + 2H+(aq) + 2I–(aq)
If the maximum concentration of vitamin C is likely to be 0.00050 g mL–1, describe how you would perform the analysis. You should mention the volume of the fruit juice used and the maximum titre of iodine you would expect to obtain.
lol they're not trying to make this simple before. I feel the thinking is outside the study design a bit, but the calculations certainly aren't.
Essentially, the question wants you to describe an experiment that will tell you what the concentration of vitamin C is. They've even given away half the answer - the experiment you'll do is a titration! So you just need to explain how you would do that titration. You don't need to go step-by-step (although that would be one way to answer it - it wouldn't be wrong, certainly), but you need to explain roughly how you'd go about it. Eg, "I would pour the fruit juice all over the bench, then add iodine until there's a colour change and I reach the end point". Things to think about:
-This is a titration. So, you're going to have something in a burette, and something in a conical flask. What do you think would make more sense to put where, and how much of each are you going to put in where?
-If the amount of vitamin C they've given is correct, how much of it will react with the iodine? What volume would that correspond to?