Help with balance of matter with chemical reaction

[Dionisio Mendoza]

The question arises in which procedure to follow, a balance by element or by compound?
The excersise is this:
A mineral of a process contains contains 90% FeS2 and 10% inerts by weight. This materialit is calcined with 25% excess air, according to the reaction:

FeS2 + 02 ► Fe203 + S02

The solid mixture leaves the calciner with 13% inerts by weight and the rest FeS2 and Fe203

a) Calculate the weight of solids leaving the calciner.

b) Determine the% conversion based on FeS2 •

c) Calculate the Orsat analysis of the gases produced.

So far i only be able to averigue the O2 and N2 wheights.

 

[Chestermiller]

Your handwritten solution is unreadable. Please describe what you did, including your reasoning for each step. The only thing I got out of your writeup is that you started by choosing a basis of 100 g for the FeS2. This was a good start.

 

[Dionisio Mendoza]

What I did first was to make the flow diagram, then calculate the theoretical moles of oxygen with the calculation base of 100g 90% FeS2 in the feed, obtaining
theoretical oxygen = 90g * 11/4 = 2.06
Then calculate the excess oxygen = theoretical oxygen * excess airflow = 2.06 * .25 = .515moles
After the total oxygen = 2.06 + .515 = 2.575moles
with a rule of three I got that the N2 would be 9.68 mole.
Multiply each one of those values by their molecular weight and the result that I obtained added them and got 581.02 grams, which would be total weight of air

 

[Chestermiller]

I confirm your moles of O2 and N2. But I get the total number of grams of air as 355.4 gm.

How did you calculate the number of grams of solids leaving the container? I get 76.92 gm. What are the number of moles of Fe atom leaving the container in the solids?

 

[Dionisio Mendoza]

[QUOTE = "Chestermiller, post: 6134226, miembro: 345636"] Confirmo sus moles de O2 y N2. Pero obtengo el número total de gramos de aire como 355.4 gm.

¿Cómo calculaste la cantidad de gramos de sólidos que salen del contenedor? Tengo 76,92 gm. ¿Cuál es el número de moles de átomo de Fe que sale del contenedor en los sólidos? [/ QUOTE]

Multiplica el número de moles de oxígeno por su peso molecular, como el N2.
2.575 mm * 32 g / mol = 309.98 g
9.68 mm * 28 g / mol = 271.04 g
Y sumando ambos obtuve el aire total.El número de lunares que salen de Fe no lo sé.

 

[Chestermiller]

[QUOTE = "Chestermiller, post: 6134226, miembro: 345636"] Confirmo sus moles de O2 y N2. Pero obtengo el número total de gramos de aire como 355.4 gm.

¿Cómo calculaste la cantidad de gramos de sólidos que salen del contenedor? Tengo 76,92 gm. ¿Cuál es el número de moles de átomo de Fe que sale del contenedor en los sólidos? [/ QUOTE]

Multiplica el número de moles de oxígeno por su peso molecular, como el N2.
2.575 mm * 32 g / mol = 309.98 g

2.575 X 32 = 82.4

 

[Chestermiller]

The number of moles of Fe atoms leaving the container in the solids is the same the number of moles of FeS2 entering. (There is no Fe in the gas).

 

[Dionisio Mendoza]

[QUOTE = "Chestermiller, post: 6134230, miembro: 345636"] 2.575 X 32 = 82.4 [/ QUOTE]
O god I am wrong its 353.44g of total air

 

[Dionisio Mendoza]

and the moles of the entry if they are .75?

 

[Chestermiller]

and the moles of the entry if they are .75?

Correct. So the total mass of solid leaving is 76.92 gm, and, since the mass of inserts is 10 gm, the total mass of FeS2 plus Fe2O3 leaving the container is 66.92. Let x = mass of FeS2 exiting and let (66.92-x) = mass of Fe2O3 exiting. In terms of x, what is the number of moles of FeS2 exiting, and what is the number of moles of Fe2O3 exiting? Based on this, in terms of x, what is the number of moles of Fe atoms exiting?

 

[Dionisio Mendoza]

but how you obtain the 76,92 g

 

[Chestermiller]

but how you obtain the 76,92 g

$$0.13 y = 10$$

 

[Dionisio Mendoza]

$$0.13 y = 10$$

Oh rigth. but in the other I do not follow you

 

[Chestermiller]

If the total solids in the exit is 76.92 gm, and the mass of inerts in the exit stream is 10 gm, what is the combined mass of FeS2 and Fe2O3 in the exit stream?