# How Do You Balance Complex Chemical Equations in Ionic and Neutral Forms?

• 1question
In summary, the author attempted to solve an equation for Cu3AsS4, but got stuck on the neutral form. They then explained how to balance charge and why the hydrogen was on the right.
1question

## Homework Statement

Write the balanced chemical reactions in ionic and neutral forms for:
i) Enargite leaching by sodium bisulfide in basic solution to form chalcocite and thioarsenate.
ii) Oxygen pressure oxidation of As2S5 in acid solution to form scorodite. Assume all sulfide sulfur forms sulfate. (Assume that ferric ion is present in solution).

N/A

## The Attempt at a Solution

i) Cu3AsS4 + HS- = Cu2S + AsS43-
Balancing:
Cu3AsS4 + HS- = 3/2Cu2S + AsS43-
Cu3AsS4 + HS- = 3/2Cu2S + AsS43- +H+
Cu3AsS4 + HS- +e-= 3/2Cu2S + AsS43- +H+

? I cannot seem to balance the last equation properly. I do know that the e- present in the equation means that there should be 2 half reactions, not one as above, but cannot figure those out either.

ii) As2S5+O2 = AsO43-+SO42-

Left side:
As2S5 = AsO43-+SO42-
As2S5 = 2AsO43-+5SO42-
As2S5+28H2O= 2AsO43-+5SO42-
As2S5+28H2O= 2AsO43-+5SO42-+56H+
As2S5+28H2O= 2AsO43-+5SO42-+56H++40e-

Right side:
O2 = ?
O2 = 2H2O
O2 + 4H+= 2H2O
O2 + 4H++4e-= 2H2O

Add together (and cancel out e-):
As2S5+28H2O= 2AsO43-+5SO42-+56H++40e-
10*(O2 + 4H++4e-= 2H2O)

Ionic Form ===> As2S5+8H2O+10O2 = 2AsO43-+5SO42-+16H+

It is balanced (I checked).

But, I get into trouble when I try to get the neutral form. Nothing on the right requires ferric (the cation I use to put all aq terms into neutral form), thus there is an imbalance of iron. Also, how do I deal with the 2H2O that appears as part of scorodite? Do I just assume that it has become part of the solution?

EDIT: Figured out 1)ii) Use H+ (and NOT ferric, Fe3+) as the cation to turn products into neutral compounds (and thus the entire reaction into neutral form).
i.e. As2S5+8H2O+10O2 = 2H3AsO4+5H2SO4

Last edited:
1question said:
i) Enargite leaching by sodium bisulfide in basic solution to form chalcocite and thioarsenate.

In basic solution means you should use water and OH- to balance hydrogen and oxygen. I don't see them in your equation.

Have you tried to decide what is getting oxidized and what is getting reduced?

I solved it:

Cu3AsS4 + 3/2HS- = 3/2Cu2S + AsS43-

I can't believe I didn't see that earlier. Thanks for the reply!

(Why can't I edit my post after a given amount of time? It would be nice to be able to grab the formatted stuff from there and change it to suit my current needs...)

1question said:
Cu3AsS4 + 3/2HS- = 3/2Cu2S + AsS43-

And where is the hydrogen on the right?

(Why can't I edit my post after a given amount of time? It would be nice to be able to grab the formatted stuff from there and change it to suit my current needs...)

I am afraid we had to do so because some people abuse the editing system. Locking the post means you can't edit the post once caught on posting nonsense.

@Borek Yes, the 3/2H+ on the right exists, I just didn't put it on here, sorry.

Ah, I see. Thanks.

What about balancing charge? -3/2 on the left, -3 on the right.

## 1. How do you balance a chemical reaction?

In order to balance a chemical reaction, you must ensure that the number of each type of atom on the reactant side is equal to the number of each type of atom on the product side. This can be done by adjusting the coefficients (numbers in front of each molecule) until the equation is balanced. It is important to note that you cannot change the subscripts (numbers written below and to the right of each element) as this would change the chemical formula.

## 2. Why is balancing a chemical reaction important?

Balancing a chemical reaction is important because it follows the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. By balancing the equation, we are ensuring that the same number of atoms are present on both sides of the reaction, thus following this law.

## 3. What are some tips for balancing chemical reactions?

One tip for balancing chemical reactions is to start by balancing the elements that appear in only one molecule on each side. Another tip is to balance polyatomic ions as a whole rather than individual elements. It is also helpful to double check your work and make sure that the number of each type of atom is equal on both sides of the equation.

## 4. How do you know when a chemical reaction is balanced?

A chemical reaction is considered balanced when the number of each type of atom is equal on both sides of the equation. This means that the coefficients (numbers in front of each molecule) are the same on both sides and the subscripts (numbers written below and to the right of each element) have not been changed.

## 5. Can chemical reactions be balanced algebraically?

Yes, chemical reactions can be balanced algebraically by setting up a system of equations for each element and solving for the coefficients. However, this method can be more time-consuming and it is recommended to use the trial and error method of adjusting coefficients until the equation is balanced.

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