Life Sciences lab classes explained

If you work in a lab you will have to make up   stock solutions   of chemicals all the time - on Tuesday you will be getting some more practise at this, and I have already written a post that goes over how to correctly go about dissolving your chemical and making it up to the correct volume ( see previous post on making up stock solutions ).  But what about how you  calculate   how much chemical you want to weigh out in the first place? Here is a simple example.... Imagine you want to make 500 mls of a NaCl solution that has a concentration of 2 M. This is how I would go about figuring out how much NaCl I would need to weigh out if I was preparing this solution: First, I would write down a couple of my all time favourite equations   that are going to help me with this problem: Ok, so my aim is to figure out  what mass of NaCl I need to weigh out  - you can find  mass  in the equation on the right. But in order to figure out the...

In practical 3 you are going to have to make a  stock solution  f rom powdered glucose. There is a very definite correct and accurate way to do this that you will have to follow -  I thought I'd give you a nice pictorial guide here to try to help you remember what to do, and why!! First of all, what is a stock solution?   Well this is simply a concentrated solution of something that you can then use to make other solutions from by diluting it down and maybe also mixing it with other solutions. So, how do you go about making a stock solution?   Before you start you would have to calculate how much chemical you need to weigh out in order to make a solution of the concentration you require in the volume you want ..... Once you have done this you have to: And voila, you have a stock solution!