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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

What concentration of HCl do you send out for the sodium carbonate standardisation prac? The text book asks for concentrated but I'm not giving them that! RiskAssess has 8-10M is ok for 11&12. (Conc. is teacher only).

Not a great lot of help, Rosalie but our guys do a standardisation of NaOH and they get 0.1M NaOH and 0.1M HCl.

I agree - wouldn't give them conc acid

Merilyn1 wrote: ↑20 May 2024, 14:22 Not a great lot of help, Rosalie but our guys do a standardisation of NaOH and they get 0.1M NaOH and 0.1M HCl.

I agree - wouldn't give them conc acid

That's the one I am familiar with. I think they're using new textbooks this year. New teacher as well. Brick cleaner was the alternative "brick cleaner or concentrated HCl" so I looked up brick cleaner and it's about 1.4M so I've said to the teacher I will give 2M and hopefully it works... Now that I think about it, I should probably find out what M they've made up for their standard solution and give something similar to that! Good to know I'm not just being overly stingy or cautious though

LOL! I get worried about giving some teachers conc HCl.