Stoichiometric reactions with weight percent

In summary, the conversation involves a question about calculating the amount of aqueous HF needed for a chemical reaction, using the given information of concentration and volume. The steps taken involve finding the moles of Th(4+), converting to moles of HF, and then determining the grams of HF needed for a 50% excess. The final answer is 0.627g.
  • #1
emc92
33
0
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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  • #2
How many moles of F- do you need? What mass of HF will contain this number of moles?
 
  • #3
i tried to solve it again..
i came up with 0.627g. is this right?
 
  • #4
Show how you got it.
 
  • #5
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
 
  • #6
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.
 

1. What is a stoichiometric reaction with weight percent?

A stoichiometric reaction with weight percent is a chemical reaction in which the reactants are combined in precise proportions based on their weight percent. This ensures that the reactants are in the correct ratio for the reaction to take place.

2. How is weight percent calculated in stoichiometric reactions?

Weight percent is calculated by dividing the mass of a specific element in a compound by the total mass of the compound and multiplying by 100. This will give the percentage of that element in the compound by weight.

3. Why is weight percent important in stoichiometric reactions?

Weight percent is important in stoichiometric reactions because it allows for precise measurement and control of the reactants. This ensures that the reaction will proceed as expected and produce the desired products.

4. How does weight percent affect the outcome of a stoichiometric reaction?

The weight percent of the reactants directly affects the outcome of a stoichiometric reaction. If the weight percent is not accurate, the reaction may not proceed as expected and the resulting products may be different than intended.

5. Can weight percent be used to determine the amount of product produced in a stoichiometric reaction?

Yes, weight percent can be used to determine the amount of product produced in a stoichiometric reaction. By calculating the weight percent of the reactants and knowing the balanced chemical equation, the amount of product produced can be determined. This is helpful in determining the efficiency of the reaction and predicting the amount of product that will be produced.

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