[Bers55]

For my chemistry science fair project I have to do this lab.  You mix NaClO_(l) and Na₂S₂O_3(l) it's supposed to be an exothermic reaction and increase the temperature of the solution.  You keep changing the ratio of the amount of mL of each and the ratio in which all the reactants are used is the correct one.

But when I do it there is no increase in temperature.  The only thing I could think of is that the bleach has partially been decomposed, but I got it somewhat recently (two months ago) and it's been in a sealed container.  Does NaClO decompose that fast?  Could I use store bought bleach?  It says I need .5M and store bought bleach only comes in %.  Also would it work if I used Ammonia instead?  And lastly is it possible that I'm doing something else wrong?

I'm kinda asking a lot here but any help would be appreciated.

[cliverlong]

I suppose one simple test of the "Potency" of the bleach is to add a few drops of dilute hydrochloric acid in a fume cupboard and test for chlorine production with damp litmus paper

2 H⁺ (aq) + OCl⁻ (aq) + Cl⁻ (aq)   Cl₂ (g) + H₂O (l)

Can you work out what the expected rise in temperature should be for the quantities you are using via:  :delta: H = mc :delta: T ?

Is your calorimater well insulated or could it be "sucking heat" from the reaction?

How sensitive is your thermometer?

Can you test the apparatus using a strongly exothermic reaction such as mixing acid and alkali?

Clive

[Bers55]

Well I'm using a styrofoam cup as my calorimeter .
And the thermometer is a standard one you would find in any classroom (the long glass ones with the red liquid in it).

My teacher gave me the answers so i already know how much it is going to increase by. the problem is that I can't produce those results.

I didn't think of testing the bleach with litmus paper though to see if it's still basic.  What do you need the hydrochloric acid for though?

[BetaAmyloid]

Well I'm using a styrofoam cup as my calorimeter .

I would suggest taking your styrofoam cup and docking it onto another styrofoam cup (stack the styrofoam cup you are using inside another styrofoam cup), this cuts out any chance of the table you are working on sucking the heat from the cup - causing a false temperature measurement. I also would suggest making some sort of top for the styrofoam cup, which cuts out any chance of the atmosphere sucking any heat from the solution.

I didn't think of testing the bleach with litmus paper though to see if it's still basic.  What do you need the hydrochloric acid for though?

It allows for the production of chlorine gas and water.