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# Molecular, complete ionic, and net ionic equations

In the molecular equation for a reaction, all of the reactants and products are represented as neutral molecules (even soluble ionic compounds and strong acids). In the complete ionic equation, soluble ionic compounds and strong acids are rewritten as dissociated ions. In the net ionic equation, any ions that do not participate in the reaction (called spectator ions) are excluded. As a result, the net ionic equation shows only the species that are actually involved in the chemical reaction. Created by Sal Khan.

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• In the case of NaCl, it disassociates in Na and Cl. So, can we call this decompostiton reaction?
• No, we can't call it decomposition because that would suggest there has been a chemical change. If you dissolve crystals of NaCl in water, you get a solution of Na+ and Cl- ions, but if you evaporate the water you get back your crystals of NaCl - overall, you've gone through a cycle and nothing has changed.
• How do we know which of the two will combine to form the precipitate if we're not given (aq) and (s)?
• At ,would the formula have equal charges or not? Both sides have a charge of 0, but the different charges are different. One side has "+,-,+,-" but the other is just "+,-". Can someone help me, I'm confused.
• As you point out, both sides have a net charge of zero and this is the important bit when balancing ionic equations.

In ionic equations, precipitates, which are solids, are not written as ions. Hence, AgCl, which is a precipitate, is not written as Ag+ and Cl-.

In general, solids, gases and liquids (eg, H2O) are not written as ions when writing ionic equations.
• At , it is said that the compund breaks into individual ions, when dissolved in water. But, if this happens, they will no longer be compunds. How are they be able to retain the characterictics of the initial compund?
• When they dissolve, they become a solution of the compound. It is still the same compound, but it is now dissolved.
• So when compounds are aqueous, unlike in solids their ions get separated and can move around ?
• Yes, that's right. The ions is solutions are stabilised by the water molecules that surround them but are free to move around.
• How can you tell which are the spectator ions? Isn't NaNo also formed as part of the reaction, meaning that the Cl and Ag ions were the spectators?
• NaNO3 is very soluble in water so it isn't formed as a compound, Na^+ and NO3^- ions are instead, that is why they both are (aq).

AgCl on the other hand is not soluble in water, it precipitates out of solution, that is why its state is (s).

Spectator ions are those that appear on both sides of the equation as ions. They don't take part in the chemical reaction.

Note that NaNO3 would be formed in addition to AgCl if you removed all the water.
• Why is it that AgCl(s) is not very water soluble even though it is an ionic compound?
• In some ionic compounds the electrostatic forces holding the ions together are stronger than the ion-dipole forces attempting to disrupt the solid lattice. Essentially the amount of energy required to break the silver chloride lattice is larger than solvation by water is able to provide. So silver chloride not dissolving in water, even though one is ionic and the other is polar, is an exception to the "like dissolves like" rule.

Hope that helps.
• What if we react NaNO3(aq) and AgCl(s)? Will it react? Why?