[baqi]

hi,

I've run into a slight problem with the chem safety people regarding a chem project I was hoping to lead for grade 6 girls for a conference promoting science.

So, I wanted to do an indicator solution experiment
1. Demo : using universal indicator and dry ice
2. Hands on: exhaling CO2 (directly or with a straw) in the flask of indicator + 0.5 M NaOH solution ((here is the problem: backsplash, and accidental inhalation of the solution) (so I need to do an alternative hands on activity --> I don't know what I should substitute. Any suggestions??)
3. Polymer slime hands on. (After the slime I wanted them to add 0.5 NaOH (drop wise) to a small piece of slime ---so they could observe the effect of a base on the polymer and then add 0.5 HCl (drop wise) to see what happens to the polymer. (again there seems to be a safety problem-the girls will be wearing gloves and safety goggles but that is not enough) What else can I do to improve the safety??? --> Use a fume hood, and get the adult lab volunteers to add the acid?? any alternatives??

Thanks for all your help,
Baqi  

[Mitch]

What is the 0.5 m naoh for? Can't you just use it without the naoh?

[baqi]

Yeah, that was pretty vague!!

The NaOH is to make the solution basic (i.e. 25mL of water 3mL of 0.5M NaOH and 2mL of indicator solution) so when they exhale CO2 into flask. The CO2 reacts with the water it acts as a weak acid and it causes a pH change.

Bc I am doing a dry ice demo (basically using dry ice as a CO2 source--I thought it would be neat if they exhale CO2 into the flask!!)
---Just an hands on application of the dry ice demo. But, I am having trouble having it approved because of the hazard of having the it splash or inhaled!!
baqi

[Echooo]

2. Hands on: exhaling CO2 (directly or with a straw) in the flask of indicator + 0.5 M NaOH solution ((here is the problem: backsplash, and accidental inhalation of the solution)

Maybe a one-way valve might help with any accidental inhalation? I've seen some about the size of a straw before.

Seems to me something could be rigged up to stop any backsplash as well.

[LQ43]

The NaOH is to make the solution basic (i.e. 25mL of water 3mL of 0.5M NaOH and 2mL of indicator solution) so when they exhale CO2 into flask. The CO2 reacts with the water it acts as a weak acid and it causes a pH change.

Have no clue if this will work.... what about soaking a filter paper with the NaOH + indicator solution and have the students blow onto the soaked filter paper - should prevent enough backsplash. But I agree still a potential for hazard.

[skyjumper]

Universal indicator and no NaOH in the bubble blowing setup. The acid is completely (for a chem lab) safe. .5 molar? Unless they are dripping it directly on there eyes. Iv splashed 2 and 6 molar on my hands (alright the 6 molar did hurt a little) and no adverse affects were shown.