Chalk

[rosaliemb]

Quest 2, textbook for year 8 has an experiment for exploring rate of reaction using chalk with hydrochloric acid. What do people use? Is the blackboard chalk used nowadays which is probably calcium sulphate rather than calcium carbonate OK. The idea is to think of grinding it to increase surface area, rather than be presented with ready made powder. And marble chips does not grind all that easily!
Thanks for all the help and hints I get from these forums.
Rosalie (another one)

[smiley]

We use Aspro Clear for reaction rates. It's cheap, easy and results are eminently graphable.

We first dissolve one in room temp water (100mL). Then we vary reaction rates using hot water, or breaking them in half, or crushing. The kids are supposed to propose their own variation and test it. All in all, it's a very successful prac.

Cheers, K

[lada]

We use CaCO3 powder with dil HCl, works well.
If you want it for rate of reaction , use marble chips for small surface area and the powder for large surface area.
Lada

[rosaliemb]

Thanks Lada and Smiley
I have recomended Aspro Clear to teachers.
Rosalie

[Prima]

Found this thread yesterday and it saved my life - the Aspro Clear works perfectly! Much more effective (as well as a lot easier in every respect) than the chalk and HCl! Now to start preparing about 200 setups for Year 8. Thank you - once again ChemTalk to the rescue