Chemistry: How do I write an ionic equation for this reaction?

• HunterDX77M
In summary: Thanks for the input!In summary, Homework Statement states that the student is having difficulty with a HW problem, and is looking for help. After attempting to solve the problem on their own, they find that Wolframalpha is not able to help and they are stuck. They end their summary by asking if there is any way to do the problem with the assumption that the compounds do not completely separate.
HunterDX77M

Homework Statement

I was doing this problem for HW online, that asks to write the ionic equation for a reaction, but I'm completely stuck. After using all my attempts (i.e., I can no longer submit the answer even if it is right, ) I still couldn't get the right answer. We've only done very simple ionic equations in class, so I couldn't apply what we did in class to the problem. Anyway here is the reaction to make an ionic equation for:

$$Ba(OH)_2 (aq) + H_{3}PO_{4} (aq) \rightarrow$$

Not applicable.

The Attempt at a Solution

Here is the last answer I attempted. Wolframalpha told me that the compound phosphoric acid (H3PO4) was "very soluable" so I separated it into ions. That was about all it was able to help me with. I assumed that the phosphate separated from the hydrogen atoms to combine with the barium and create an insoluable solid (according to my textbook, any non-alkali metal combined with phosphate is insoluable). So with all that, I thought the ionic equation would logically be:

$$3H^{+}(aq) + 2{PO_4}^{-3}(aq) + 3Ba^{+2}(aq) + 2OH^{-}(aq) \rightarrow Ba_3(PO_4)_2(s) + 3H^{+}(aq) + 2OH^{-}(aq)$$

This is wrong as my fifth and final attempt told me . . . The super vague reason the system gives me for this being wrong is that "Your answer contains an ambiguous or incomplete reaction equation. Check all the components on the reactant-side of the equation. Check all the components on the product-side of the equation." If you need anymore information on my thought process or anything like that, please ask. Thanks in advance for any help.

Do you need to remove the spectator ions?

BloodyFrozen said:
Do you need to remove the spectator ions?

For the net ionic equation, yes, I have to remove the spectator ions. But for this equation (just the plain old ionic equation) I must keep the spectator ions.

H++OH- - don't you think they will react?

Phosphoric acid is soluble, but it is a weak acid, so it is not dissociated completely.

Barium hydroxide is weakly soluble, but it is a strong base, so it is completely dissociated.

It is a little bit tricky if you ask me. Not clear to me what they can expect.

Borek said:
H++OH- - don't you think they will react?

Umm, do they make water? I'm not sure.

Borek said:
Phosphoric acid is soluble, but it is a weak acid, so it is not dissociated completely.

How do you represent something that only partially dissociates in the equation, though?

HunterDX77M said:
Umm, do they make water? I'm not sure.

Yes.

How do you represent something that only partially dissociates in the equation, though?

That's why I have no idea what kind of answer they expect. 1M solution of phosphoric acid acid is approximately 8% (H++H2PO4-) and 92% H3PO4. It is not something you can write in a simple way.

Borek said:
1M solution of phosphoric acid acid is approximately 8% (H++H2PO4-) and 92% H3PO4.

Wow we definitely didn't learn that in class. I think based on other problems we're supposed to make the simplifying assumption that the compounds either completely separate or don't separate at all. Is there any way to do this problem with that in mind?

The closest would be to assume molecular (undissociated) H3PO4.

1. What is an ionic equation?

An ionic equation is a type of chemical equation that shows the chemical species that are involved in a reaction, specifically those that are present in their ionic form. This type of equation is commonly used in reactions involving ionic compounds.

2. How do I determine which species are ionic in a reaction?

In order to write an ionic equation, you must first identify the ionic compounds that are present in the reaction. These are typically compounds that contain a metal and a nonmetal, or a polyatomic ion.

3. What is the process for writing an ionic equation?

The process for writing an ionic equation involves separating the reactants and products into their respective ions, and then canceling out any spectator ions (ions that are present on both sides of the equation and do not participate in the reaction). The remaining ions are then written as the ionic equation.

4. Can you provide an example of an ionic equation?

Sure! Let's take the reaction between sodium chloride (NaCl) and silver nitrate (AgNO3) as an example:

NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)

The ionic equation for this reaction would be:

Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) → Na+(aq) + NO3-(aq) + AgCl(s)

5. What is the significance of writing an ionic equation?

Writing an ionic equation can help to simplify a chemical reaction and focus on the species that are actually participating in the reaction. This can also make it easier to balance the equation and determine the products of the reaction.

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