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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: FouRRaW on February 14, 2007, 09:20:57 PM

Title: PbCO3
Post by: FouRRaW on February 14, 2007, 09:20:57 PM

How do you know that PbCO₃ is a solid?
I'm supposed to write out the total net ionic equation of Pb(NO₃)_2(aq) and Na₂CO₃.

And i know that when double replacement happens PbCO₃ is a solid but the other is aqueous, because my teacher said so?
Why is it a sold, how do you know it is a solid and how do you figure it out when doing a net ionic equation?

Anybody know? Help Appreciated, thanks.

Title: Re: PbCO3
Post by: constant thinker on February 14, 2007, 09:32:27 PM

Start with a regular balanced equation.

You already know you have:
Pb(NO₃)₂ (aq) + Na₂CO₃ (aq) -->

You said it was double displacement, which it is. The products shouldn't be heard to predict. You also already know that one of your products is PbCO₃, and that it will be your precipitate (the solid).

Title: Re: PbCO3
Post by: FouRRaW on February 14, 2007, 09:48:30 PM

okay, i'm just wondering how my teacher knew that PbCO₃ was a solid?

(oh and in the original question both compounds are aqueous)

Title: Re: PbCO3
Post by: constant thinker on February 14, 2007, 09:51:05 PM

A lot of lead compounds are insoluble I believe. He probably found out originally from looking a solubility table. They're really useful.

Title: Re: PbCO3
Post by: FouRRaW on February 14, 2007, 09:53:05 PM

okay, so there was no way of figuring it out in your head? Or could you some how figure out that PbCO₃ is insoluble?

Title: Re: PbCO3
Post by: Yggdrasil on February 14, 2007, 09:56:54 PM

AFAIK, the only way you could know that PbCO₃ is insoluble is by looking it up in a solubility table.  It's one of those things in chemistry that's been determined purely empirically.

By the way, if anyone has a more theoretical explanation of why certain salts are soluble which can predict solubility, I'd love to hear it.

Title: Re: PbCO3
Post by: FouRRaW on February 14, 2007, 09:58:05 PM

Thank you so much, what does AFAIK MEAN?

Title: Re: PbCO3
Post by: Yggdrasil on February 14, 2007, 09:58:56 PM

AFAIK = as far as I know

Title: Re: PbCO3
Post by: AWK on February 15, 2007, 01:41:04 AM

Quote from: FouRRaW on February 14, 2007, 09:48:30 PM

okay, i'm just wondering how my teacher knew that PbCO₃ was a solid?

(oh and in the original question both compounds are aqueous)

Therer are some simple solubility rules come from chemist experirence, eg only carbonates od alkali metals (Li, Na, K Rb, Cs) and ammonia are soluble in water.
Search internet for solubility rules. They are quite simple if you know some inorganic chemistry and a periodic table