HELP! confused about chemistry!?

Question

people have been trying to heelp me but i still dont understand...

write the net ionic equation corresponding to the precipitation reaction that occurs.

a) Na+(aq) + Cl-(aq) + Ag+(aq) + NO^3-(aq) - AgCl (s) + Na+ (aq) + NO^3- (aq)

b) 2 NH^4+(aq) + CO^3^2-(aq) + Ca^2+(aq) + 2 CI-(aq) - CaCO^3 (s) + 2NH^4+(aq) + 2CI- (aq)

c) Pb^2 (aq) + 2 NO^3- (aq) + 2 H+(aq) + 2 Br- (aq) - PbBr^2 (s) + 2 NO^3- (aq) + 2 H+(aq)

d) Fe^2+ (aq) + 2 CI- (aq) + 2K+(aq) + S^2- (aq) - FS (s) + 2 CI- (aq) + 2 K+(aq)

Answer 1

we have to cancel any duplication of species on the left and right side.
a) Cl-(aq) + Ag+ (aq) >> AgCl(s)
b) Ca2+ (aq) + CO32- (aq) >> CaCO3 (s)
c) Pb2+ (aq) + 2 Br- (aq) >> PbBr2 (s)
d) Fe2+ (aq) + S2- (aq) >> FeS (s)

Answer 2

The net ionic reaction is the one that makes the reaction "go" by forming an insoluble salt, a gas (which escapes), or an only slightly ionized substance (H2O or a weak acid). Formation of any of these types of products takes ions out of the reaction. The other ions are "spectator ions:" They're just sorta there.

a) Cl-(aq) + Ag+(aq) ===> AgCl(s)
b) CO3=(aq) + Ca2+(aq) ===> CaCO3(s)
c) Pb2+(aq) + 2Br-(aq) ===> PbBr2(s)
d) Fe2+(aq) + S=(aq) ===> FeS(s)

Answer 3

Cancel out the ions that "are common on both sides of the equation" and are spectator ions to get the net ionic equation:

a) Ag+(aq) + Cl-(aq) --> AgCl(s)
b) Ca+2(aq) + CO3-2(aq) --> CaCO3(s)
c) Pb+2(aq) + 2Br-(aq) --> PbBr2(s)
d) Fe+2(aq) + S-2(aq) --> FeS(s)

Answer 4

Think about the definition of 'net'. Basically this is like a math equation.
Each value on each side will cancel out. For example, on the first equation, the Na+'s and the NO3- are present on both sides of the equation. Therefore you can cancel them to be zero on both sides. Now what are you left with?
The parts that do not cancel out, which are Ag+ and Cl- on one side...why? Because it is a solid, or 'percipitate', on the right hand side of the equation.

Yeah ok - the people above me are right, but don't just copy their answer. This is one of the cornerstones of chemistry, so please try to understand WHY they are right.