In an ionic equation, how do you know what pairs with what? For example:?

[land_of_ice]

molecular:
Pb(NO3)2 (aq) + 2 KI (aq) ----->2KNO3 (aq) + Pbl2 (s)
Ionic equation
Pb2+ (aq) + 2NO3- (aq) + 2 K (aq) + 2 I- (aq)----->2K+ (aq)+ 2NO3- (aq) + PbI2 (s)

I know why they break apart in the ionic part, its because ionic things aer broken up, but how would you know that they join together to form 2K+ (aq)+ 2NO3- (aq) + PbI2 (s) at the end? like in that order?

and one more question, how do you know that when certain things join together, that they form a solid, such as they way PbI2 (s) forms, because at first Pb was (aq), and I2 was (aq) also

 

[Borek]

how would you know that they join together to form 2K+ (aq)+ 2NO3- (aq) + PbI2 (s) at the end? like in that order?

Order doesn't matter, 2NO3- (aq) + PbI2 (s) + 2K+ (aq) is perfectly valid. Note that K⁺ and NO₃^- should be removed, as they are just spectators.

how do you know that when certain things join together, that they form a solid, such as they way PbI2 (s) forms, because at first Pb was (aq), and I2 was (aq) also

Do you know solubility rules?

 

[land_of_ice]

Order doesn't matter, 2NO3- (aq) + PbI2 (s) + 2K+ (aq) is perfectly valid. Note that K⁺ and NO₃^- should be removed, as they are just spectators.



Do you know solubility rules?

Can you explain how it uses the solubility rules? Because That's the part I don't understand. I know the solubility rules, just not how the solubility rules affect it and thanks so much for the help

 

[Borek]

You have four ions present: K⁺, Pb²⁺, I^-, NO₃^-. Basically you check all combinations that can create a salt (that means cation and anion) and you check if it is soluble or not.

In this particular case there are following combinations possible (do you see why?):
K⁺ & I^-
K⁺ & NO₃^-
Pb²⁺ & I^-
Pb²⁺ & NO₃^-

Try to apply solubility rules to find out which of the possible salts is insoluble and will precipitate.