Limiting Reactant & Excess Reactant Calculation for CaF2 + H2SO4

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In summary, the conversation is about understanding limiting reactants and determining the amount of product that can be formed. The given information includes adding 10.0g CaF2 and 10.0g H2SO4 to 1L H2O, and the chemical equation is CaF2 + H2SO4 -> CaSO4 + 2HF. The limiting reactant is H2SO4, meaning that CaF2 is in excess. The calculations for the amount of CaSO4 and excess CaF2 are not entirely accurate due to rounding errors.
  • #1
in the rye
83
6
Homework Statement

I wanted to check my work on this to make sure I'm understanding limiting reactants.

You added 10.0g CaF2 to 10.0g H2SO4 to 1L H2O
1. How much CaSO4 can you possibly make?
2. Which is the limiting reagent?
3. Which reactant is in excess? By how much?

The attempt at a solution

CaF2 + H2SO4 -> CaSO4 + 2HF

10g CaF2(1 mol CaF2/78g CaF2) = 0.13 mol CaF2
10g H2SO4(1mol H2SO4/98H2SO4) = 0.10 mol H2SO4

I believe this answers questions 2 and 3. The limiting reactant is H2SO4, meaning the reactant that is in excess is CaF2. For this part since it is 1:1 I assumed that I'd subtract 0.10 from 0.13 and I was left with 0.03 mol CaF2. Converting that back to grams:

0.03 mol CaF2(78g CaF2/1 mole CaF2) = 2.34g CaF2

Then for 1 I got:
10g H2SO4(1 mole H2SO4/98g H2SO4)(1 mole CaSO4/1 mole H2SO4)(136g CaSO4/1 mole CaSO4) = 14g CaSO4

1. 14g CaSO4
2. H2SO4
3. 2.34g CaF2

I don't mind if my math is a tad off, I'm more concerned with the concept at this point. Thanks for your time, again. :)
 
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  • #2
It looks OK to me.

Chet
 
  • #3
Chestermiller said:
It looks OK to me.

Chet

Thanks Chet, appreciate you. :)
 
  • #4
Logic is OK, math not so.

Watch your significant figures. 14g of CaSO4 is in the right ballpark, but it should have 3 sigfigs, not 2.

Don't use rounded down amounts in your calculations. Use as many digits as you have (but report the rounded down values). Because of rounding errors your mass of excess CaF2 is off by about 15%.
 

1. What is a limiting reactant?

A limiting reactant is the substance in a chemical reaction that is completely consumed, thus limiting the amount of product that can be formed.

2. How do you determine the limiting reactant in a reaction?

To determine the limiting reactant, you must first write out a balanced chemical equation. Then, calculate the moles of each reactant present. The reactant with the lower number of moles is the limiting reactant.

3. What is an excess reactant?

An excess reactant is the substance in a chemical reaction that is left over after the limiting reactant is completely consumed. It is present in a greater amount than what is needed for the reaction to occur.

4. How do you calculate the amount of excess reactant remaining after a reaction?

To calculate the amount of excess reactant remaining, you must first determine the moles of the limiting reactant that were consumed. Then, use the balanced chemical equation to calculate the moles of the excess reactant used. Finally, subtract the moles of excess reactant used from the initial moles of excess reactant to determine the amount remaining.

5. Can you have more than one limiting reactant in a reaction?

Yes, it is possible to have more than one limiting reactant in a reaction. This occurs when the reactants are present in a ratio that does not match the ratios in the balanced chemical equation. In this case, the reactant that produces the least amount of product is the limiting reactant.

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