Gchem Problem

[StudentDoc1234]

---

Members do not see this ad.

Can someone please help me out with this problem. Not sure where to start to figure this out. The correct answer is E.

 

[onlykhs]

.

 

[StudentDoc1234]

I'm not sure, but I think the correct answer is C

The answer is E.... here is an explanation for it but it's still not clear to me.

 

[onlykhs]

.

 

[cacajuate]

Thats the most complicated explanation ever.

This is how I solve it. When looking for the conc of Mg3(PO4)2, use this formula N1M1V1=N2M2V2. N=normality. Mg3(PO4)2 has a normality of 3. so

(.005 L)(.005 M MgCl2)= (3)(M2)(.015L) You solve for M2. That give you the concentration of Mg3(PO4)2. Then you just subtract the mole amount of Mg2+ from the concentration found above.

Basically

mole Mg2+ - ((N1M1V2/N2V2)

 

[StudentDoc1234]

Thats the most complicated explanation ever.

This is how I solve it. When looking for the conc of Mg3(PO4)2, use this formula N1M1V1=N2M2V2. N=normality. Mg3(PO4)2 has a normality of 3. so

(.005 L)(.005 M MgCl2)= (3)(M2)(.015L) You solve for M2. That give you the concentration of Mg3(PO4)2. Then you just subtract the mole amount of Mg2+ from the concentration found above.

Basically

mole Mg2+ - ((N1M1V2/N2V2)

Okay that clears a lot up for me but I don't understand why are we subtracting Mg2+ moles at the end? The question asks for the concentration of Mg3(PO4)2, isn't M2 from
(.005 L)(.005 M MgCl2)= (3)(M2)(.015L) supposed to be the concentration of Mg3(PO4)2?

 

[StudentDoc1234]

Anyone? Is it really that obvious?

 

[cacajuate]

Honestly have no idea. I deduced that from the answer choices.

Doubt you will see something on the DAT that complicated. Probably just find the concentration of mg3(po4)2