September 18, 2019, 04:40:30 PM
Forum Rules: Read This Before Posting


Topic: Need help identifying and understanding limiting reagents  (Read 683 times)

0 Members and 2 Guests are viewing this topic.

Offline demvp_demar

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Need help identifying and understanding limiting reagents
« on: March 09, 2019, 06:28:43 PM »
We did a lab yesterday and here are the results:


Pb(NO3)2+ 2KI   → 2KNO3 + PbI2

We had 0.95g of Lead (II) Nitrate and 1.10g of Potassium Iodide.

I've converted Pb(NO3)2 to Moles which gave me 0.00286 moles.

1.10g of KI2 are 0.00662 moles.

How do I find the limiting reagent and what are the steps specifically.

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 6558
  • Mole Snacks: +472/-79
  • Gender: Male
Re: Need help identifying and understanding limiting reagents
« Reply #1 on: March 09, 2019, 07:23:06 PM »
  Pb(NO3)2   +     2KI         → 2KNO3 + PbI2
0.00286 mol  0.00662 mol
What you can see?
AWK

Offline demvp_demar

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Re: Need help identifying and understanding limiting reagents
« Reply #2 on: March 10, 2019, 03:10:31 AM »
Yea I got that part. But do I have to divide by the coefficients after? Or can I always just look at the moles and decide?

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 6558
  • Mole Snacks: +472/-79
  • Gender: Male
Re: Need help identifying and understanding limiting reagents
« Reply #3 on: March 10, 2019, 05:21:24 AM »
0.00286 mol  0.00662 mol - starting reagents
         ?                ?           - after reaction - which is null, and which in excess
AWK

Offline chenbeier

  • Full Member
  • ****
  • Posts: 569
  • Mole Snacks: +55/-13
  • Gender: Male
Re: Need help identifying and understanding limiting reagents
« Reply #4 on: March 10, 2019, 03:25:42 PM »
Or in other words.

In the Equation you have a ratio 1 to 2.

Combine and compare it with the given values.

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 3807
  • Mole Snacks: +242/-16
Re: Need help identifying and understanding limiting reagents
« Reply #5 on: March 12, 2019, 09:49:02 AM »
It is the possible moles of product that one can make that is the key.  In order to know this, you have to use the stoichiometric coefficients and obey the normal rules of units cancellation.

Sponsored Links