Australia's Science Forum

Do you, labbies out there, titrate and work out the molarity of standards?
I have a replacement coming for next term and I hope he can do it, as I have always done it for the chemistry teachers.
Is this part of our job, or just to make it the standards and let teacher work it out?

Lada

I don't do it. If something needs standardising it is usually part of the prac to make up their own standard solution and calculate the exact molarity of whatever they are standardising. Otherwise, as far as I know, the measurements I do when making up solutions are good enough. I am always as accurate with my weighing solids and measuring liquids as I can be.

Same here. Our kids make their own solutions and then do their own calculations.

Hi Lada,
The kids here make their own standard Sodium carbonate, then use this to titrate against some hydrochloric that I provide. But I adjust the molarity, so it gives a good titration, and this involves titrating and standardising I guess. I do the same for another prac that involves vinegar and sodium hydroxide. I quite enjoy it! Like you, all my years of titrating come to the fore, and my results are excellent!
Ellice

Yeah They do thier own here too. As long as they have the exact measurements for the soulitons I have prepared they should be able to do the calculations for themselves.

The standardisation is part of the Chemistry course - so i do not do it..
I make the usual bulk lab solutions which are roughly Molar etc. but anything more precise is up to teachers - remember they get PAID to do this and they get paid much more than we do - so don't fall for it!

I'm with sunray18. Not part of our duties. We are really only meant to be gophers, intellligent ones at that

I just standardised a 0.1M NaOH solution, tried to make it stronger rather than weaker so weighed out ~8.5g NaOH for 2 litres, but it came out at 0.9025M. I used aliquots of 0.51g KHP and average of 3 titres was 27.7ml - all in close range. There's only ~1% impurities listed on the NaOH pack so I'm guessing the pellets have absorbed some moisture from the air. Is my math OK or something else wrong?

whoops, meant 0.0902M

wher