[toadesque]

Just a little background information

I did a lab. I had to measure the temperature of NaoH and HCL. I had to do that for 5 minutes. On the 6th minute I mixed the 2 solutions together and then for another 15 minutes I measured the temperature of the mixture. OK

Now it wants me to graph my information.

So for example I have

HCL
0 minute - 23.8
2 minutes - 23.1
4 minutes: 22.9

NaOH
1 minute - 22.5
3 minutes - 22.5
5 minutes: 22.5

Then on the 6th minute I mixed them together. On the 7th minute I started recording the temperature again. The temperature sky rockets here, to like 35 degrees.

OK so now I have to graph this. This is the part I'm not understanding, It says:

"You must hand in a graph of temperature vs time, from which you will determine of the temperature at time ox mixing for the run"

I have to find Delta T, so basically the change in temp. But what I don't understand is does it want me to use the Final Temperature which will be the mixture and subtract the Mixture at minute 7 when I first mixed them? Or does it mean from at minute 0?

I forgot to add. At minute 6 when I mix them, I just record the time of the mixing but I don't take the temperature.

[toadesque]

Also the thing that doesn't make sense is if I take my final temperature....how can I subtract the initial temperature if it's 2 different solutions? That wouldn't make sense. But if I subtract the temp from when I first mixed them, then I'll get a negative answer since the solution cools down as time passes. And that wouldn't be right.

[Borek]

:delta: T should be maximum measurement after mixing minus the last measurement before mixing. In you case that'll mean first temperature after mixing minus last before mixing, but that's not always the case. If the reaction is slow you will observe slow rise in the temperature after mixing, followed by temperature falling once the mixture starts to cool down. Then maximum measured temperature will be not first after mixing.

Problem is, you have not mixed reactants having the same temp, so you should calculate temperature of the mix assuming no reaction took place and use this value for :delta: T.

[toadesque]

Well I'm looking at the questions and it says it is necessary for me to graph this in order to find the Delta T. But the problem is I don't know how to graph it!

You said

"so you should calculate temperature of the mix assuming no reaction took place and use this value for delta T."

Not quite sure what you mean. Do you mean use the mixture temp at its peak? But what do I subtract from that?

[Borek]

What's the problem with graphing? Put time on x axis and temperature on y.

Using spreadsheet - enter data in two columns (time first, temp. second), select it, and select graph scatter (XY) type.

[toadesque]

Yeah but the whole part I'm confused about is where to start off at. Do I start my graph off with 2 lines to represent both solutions? Then  how do I show it when I mix the solutions together?

[sjb]

Problem is, you have not mixed reactants having the same temp, so you should calculate temperature of the mix assuming no reaction took place and use this value for :delta: T.

So assume you have perhaps 5 ml of water at 20°C, and 5 ml at 25°C. What's the temperature when you mix them?

I don't know what volumes of HCl and NaOH you used, but the principle is the same.

[Arkcon]

Yeah but the whole part I'm confused about is where to start off at. Do I start my graph off with 2 lines to represent both solutions? Then  how do I show it when I mix the solutions together?

A suggestion:  Try graphing all your data, then, stare at it.  Seriously.  That's why we collect data, to see what's going on, and we chart data, to make sense of it.  See if you can tell, from the chart, how it answer the question.  Maybe, just maybe, your chart will have extra data, that you won't need.  But it doesn't hurt the graph paper any to hold extraneous data.