Jump to content
Sign in to follow this  

Lab Report Measuring the enthalpy change between Zn and CUSO4

Recommended Posts

In this lab I had several problems:

* Concentration of CuSO4 was 0.2 M.

*No major changes in temperature. Min: 28 Max: 34

*Huge percentage error of 207.38%

*We had to increase the amount of CuSO4 and Zn to be able to read the temperature because the thermometer couldn´t reach it.

* We used an old polyestirene cup and a normal thermal cup's lid.

*Lab instructions told me to use 25 ml of 1.0 M of CuSO4 and 6 grams of zinc, but I used 75ml of 0.2M of CuSO4 and 18 grams of zinc.

*The graph I plotted with the data I got from the experiment is awful. Also, I was asked to trace a perpendicular line from when the zinc was added and a tangent line from the maximum point and using the temperature found at the intersection point which was 38 ºC, find the enthalpy change. The problem is that the result was horrible.

*I was given a theorical value of -217

Can you explain me how these problems could have affected my experiment and why I had a huge percentage error. Also if Ive got any mistakes I would really appreciate someone pointing them out.

Thank you everyone!

Edited by akr1

Share this post


Link to post
Share on other sites

I've sent you a few comments to your inbox. as soon as you see this please remove your file because people can take it and plagiarise (although i don't think anyone would in this case...) just to stay safe.

is it DCP only or also CE?

Share this post


Link to post
Share on other sites

I've sent you a few comments to your inbox. as soon as you see this please remove your file because people can take it and plagiarise (although i don't think anyone would in this case...) just to stay safe.

is it DCP only or also CE?

hahaaha! yeah I think NO ONE will want to plagirize what I did! hahaha! thank you although! and yes I do have to conclude and evaluate...

Share this post


Link to post
Share on other sites

ok, so firstly your graph is supposed to look like this:

tempgraph2.gif

can't find a simpler picture, sorry, but it's something like that, which means after it increases significantly, you need to still record the temperature when it goes down until you get enough data points (I'd say at least 5) that you can extrapolate it. so you can talk about this in the evaluation and suggest to record the temp for a longer time period.

and then you used wrong amounts of reactants so you definitely have to admit this mistake.

and you used a lot more zinc than required (look at the numbers of moles...) and this mass of (excess, unused) zinc adds to the mass of your thing and this excess zinc absorbs some heat, causing systematic errors because the required amount of zinc for your used CuSO4 is only 1 g. the 17 g of zinc was just sitting there absorbing heat with some unknown specific heat capacity...

We had to increase the amount of CuSO4 and Zn to be able to read the temperature because the thermometer couldn´t reach it.

what do you mean the thermometer couldn't reach it? :o

oh well you can suggest to use data logger with temperature sensor instead. more precise.

it's also true to use more amount of reactants, to reduce the uncertainties.

We used an old polyestirene cup and a normal thermal cup's lid.

woah, nice. but then why were there still a lot of errors?

you can still talk about heat loss to surroundings i guess?

one of the most important things you should mention (probably the largest source of error) is the assumption of density of both CuSO4 & Zn are 1 g/ml and their specific heat capacity is 4.18 J/gK and then you can talk about measuring their real values.

your cup still absorbs heat no matter what.

did you mix them at the exact same time? like did you pour the solid all at once or did you pour little by little?

I guess that's all? good luck hey!

Share this post


Link to post
Share on other sites

could anyone tell the literature value of the enthalpy of this reaction?

Which H do you need? In this case there's lattice, formation, and bond enthalpy XD

Share this post


Link to post
Share on other sites

Maybe you didn't keep your controlled variables constant for the two experiments. There are lots of external factors that might affect your results, including the amount of chemicals used for each trial, external temperature, pressure, etc.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.