Calculating Molarity & Volume of Cu(NO3)2

  • Thread starter Thread starter gurpalc
  • Start date Start date
  • Tags Tags
    Molarity Volume
AI Thread Summary
To calculate the molarity and volume of Cu(NO3)2, the user has 0.50 g of copper and 5 mL of 10M HNO3. The limiting reagent is copper, and the calculations indicate the number of moles of copper nitrate is likely correct. To find the final volume of Cu(NO3)2, it is suggested to assume the final volume remains close to 5 mL, despite potential changes during the reaction. Accurate calculations are hindered by the significant figures of the initial data, which introduce considerable uncertainty in the final concentration results. Understanding the limitations of the data is crucial for accurate molarity calculations.
gurpalc
Messages
16
Reaction score
0

Homework Statement



My problem is in the attachment. I am trying to find the molarity and volume of Cu(NO3)2 while I only know Cu has .50 g and HNO3 is 10M and is 5mL.

Homework Equations





The Attempt at a Solution



I have done my calculations on the right. What I have circled is what I believe to be the moles of Cu(NO3)2. The copper is limiting I assume. I don't know where to go from there. Please help.
 

Attachments

  • chem pic.jpg
    chem pic.jpg
    39 KB · Views: 443
Physics news on Phys.org


Your calculations are barely readable. Number of moles of copper nitrate seems to be OK.

You need final volume to calculate concentration. Hard to help not seeing the question, but if you are not given any other information, assume 5 mL.
 


Borek said:
Your calculations are barely readable. Number of moles of copper nitrate seems to be OK.

You need final volume to calculate concentration. Hard to help not seeing the question, but if you are not given any other information, assume 5 mL.
How do I find final volume of Cu(NO3)2. That's what I'm stuck on. I don't know how to make the calculations.
 


Have you read what I wrote?
 


Yes but I don't get it.
 


Some acid was consumed and replaced with copper. Even if the volume of the liquid changed during the reaction, it didn't change by much. This is only an approximation, but there is no better one available.

On a very general level it would be possible to calculate more exact volume given density tables of nitric acid solutions and nitric acid/copper nitrate solutions. Two problems with this idea. First, I have never seen density table for a mixture of nitric acid and copper nitrate (and I have seen plenty of density tables). Second, you are limited by the accuracy of mass and volume, as they are given with one significant digit only - using very accurate method for inaccurate data won't give a better result.

Don't read if you are already confused:
0.5 g means anything between 0.45 and 0.55 g, 5 mL means anything between 4.5 mL and 5.5 mL. That in turn means amount of copper is between 7.08x10-3 and 8.66x10-3 moles, and concentration something between 7.08x10-3mol/0.0055L=1.29M and 8.66x10-3mol/0.0045L=1.92M - almost 50% difference. Error you are making assuming final volume of 5mL is most likely not larger than 10% - so much smaller than the one already intrinsic to the data.
 
Thread 'Confusion regarding a chemical kinetics problem'
TL;DR Summary: cannot find out error in solution proposed. [![question with rate laws][1]][1] Now the rate law for the reaction (i.e reaction rate) can be written as: $$ R= k[N_2O_5] $$ my main question is, WHAT is this reaction equal to? what I mean here is, whether $$k[N_2O_5]= -d[N_2O_5]/dt$$ or is it $$k[N_2O_5]= -1/2 \frac{d}{dt} [N_2O_5] $$ ? The latter seems to be more apt, as the reaction rate must be -1/2 (disappearance rate of N2O5), which adheres to the stoichiometry of the...
I don't get how to argue it. i can prove: evolution is the ability to adapt, whether it's progression or regression from some point of view, so if evolution is not constant then animal generations couldn`t stay alive for a big amount of time because when climate is changing this generations die. but they dont. so evolution is constant. but its not an argument, right? how to fing arguments when i only prove it.. analytically, i guess it called that (this is indirectly related to biology, im...
Back
Top