Stoichiometric reactions with weight percent

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Discussion Overview

The discussion revolves around calculating the mass of 6.000 wt% aqueous HF required to provide a 50% excess for a reaction with 10.0 mL of 0.0236 M Th4+. The focus is on stoichiometric calculations related to the reaction Th(4+) + 4F- → ThF4 (s).

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant seeks help with calculating the grams of HF needed for the reaction.
  • Another participant asks how many moles of F- are required and what mass of HF would contain that number of moles.
  • A participant claims to have calculated 0.627g of HF but is uncertain about its correctness.
  • Another participant requests to see the calculations leading to the claimed mass.
  • A participant explains their calculation process, stating they multiplied the moles of Th by 4 to find the moles of HF, resulting in 9.44*10^-4 moles, which converts to 1.88*10^-2g. They then account for the 50% excess to arrive at 0.376g, leading to a total of 0.627g for the 6% wt solution.
  • One participant acknowledges understanding the calculations but points out a potential confusion between 50% and 100% excess.

Areas of Agreement / Disagreement

Participants are engaged in a collaborative problem-solving process, with some uncertainty regarding the calculations and the distinction between different excess percentages. No consensus on the correctness of the final mass calculation has been reached.

Contextual Notes

The discussion includes various assumptions about the stoichiometry of the reaction and the calculations involved, which may depend on the definitions of weight percent and the interpretation of excess.

emc92
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i can't figure out how to calculate this. Please help!

How many grams of 6.000 wt% aqueous HF are required to provide a 50% excess to react with 10.0 mL of 0.0236 M Th4+ by the following reaction?

Th(4+) + 4F - → ThF4 (s)

I found the molarity for Th(4+) to be 2.36*10^-4.. I'm not really sure where to go from here =/
 
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How many moles of F- do you need? What mass of HF will contain this number of moles?
 
i tried to solve it again..
i came up with 0.627g. is this right?
 
Show how you got it.
 
using the moles of Th, i multiplied that by 4 to find the number of moles of HF, which turns out o be 9.44*10^-4. Then i changed it to grams, giving me 1.88*10^-2g. since it said 50% excess, the total grams of HF would be 0.376g. then 6 %wt would be 0.627g
 
emc92 said:
using the moles of Th, i multiplied that by 4 to find the number of moles of HF, which turns out o be 9.44*10^-4. Then i changed it to grams, giving me 1.88*10^-2g.

OK up to now.

since it said 50% excess, the total grams of HF would be 0.376g. then 6 %wt would be 0.627g

You ate zero, but I think I know what you did. 50% excess and 100% excess are two different things.
 

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