Australia's Science Forum

Hi all,
I need to put together a prac test for Yr11 Chem that comes under Heat of Reaction. The suggested procedure is temperature of 50mLs NaOH, added to 50mLs HCl. Note rise in temperature. Then do NaOH and H2SO4. Should there be much difference in the final temperatures in these two reactions?
Any suggestions along this vein would be appreciated.
Ellice.

The addition of steel wool to copper sulfate soln(1M)_ is a good one to do....temp increase about 15 degrees.
Do it in polystyrene cups.

Shouldn't the teacher be writing the test? Does it need to be an actual reaction? Adding sodium hydroxide to water produces heat. Maybe you could get them to measure it out accurately to make 100ml of 1M or 2M NaOH and collect it at the end and keep it to save you making it up later!

Oh hey Rosalie - brilliant!

Anything to make life easier I know there are ones that get cold as they dissolve too, but not off the top of my head.

Thodium Thiosulphate I believe.

hi ellice
You shouldnt be the sucker trying to figure this one out!
Sorry..... you know who will get the blame if it all turns out wrong!
Thats why the teacher gets payed the extra bucks.
Matchstick

Hi all,
Thanks for the ideas. After a few trials, we are going to go with a procedure that involves 25mLs of NaOH added to different volumes of HCl (10, 20.....70mLs). Taking temp before and after. Kids work out heat of reaction point, do graphs, blah, blah.
Now the hard part. 46 students require 200mLs NaOH, and 300mLs HCl. I am busy gathering bottles and making BUCKETS of solutions! It's like a processing plant in here today!
Then I guess I'd better label everything with safety stuff (just thought of that). Thank heavens for Chemwatch!
Ah! Looking forward to the weekend.
Take care, Ellice.

Re: copper sulfate and steel wool reaction...

We had kids doing a prac exam last term where they put steel wool in copper sulfate. It was left in the labs over the holidays and now I have a delightful mess of brown sludge with blue crystals growing up the sides of the beakers. What do I do with this mess?? Do I keep it for disposal? Add more steel wool to remove all blue and put in the bin? Any suggestions how to get the rust stains out of the beakers? One class was transferred to one beaker but the other is still all in the individual beakers.

Can the sludge be dried out to be put in the bin? I'd scrape out the solid copper sulfate and put it in the bin, too. If it's liquid, you could let it evaporate a bit to reduce how much you have to dispose of, or you could try more steel wool. (I have to collect all my heavy metal waste, it can't go down the sink at all so never use the steel wool trick.)
As for cleaning the beakers - 4M HCl works a treat. You can keep reusing it, just label as such. To reduce how much you need, you could do one or two beakers at a time and keep pouring it into the next one. I have a batch I use for cleaning test tubes of rust stains.