posted by Anonymous .
Which of the following pairs of aqueous solutions will react when mixed?
K2CO3 + HNO3
HCl + LiOH
MgCl2 + KOH
Li2S + HCl
All of these solution pairs will produce reactions.
All, but you need to know how to tell.
There will be a reaction if one of the following is true.
1. A gas is released. You know the elements that are gases; i.e., H2, O2, N2, F2, Cl2 plus the common ones that are compounds like CO2, SO2, SO3, acetylene, etc. Rxns 1 and 4 are examples. CO2 for #1 and H2S for #4.
2. An insoluble precipitate is formed. Here is a simplified list of solubility rules.
An example is Mg(OH)2 from #3.
3. A slightly ionized material is formed. That means a weak electrolyte. H2O is an example in #2.
There are other rules for different kinds of reactions (redox reactions for example) but these three are good to remember for the non-redox reactions. Some redox reactions fall into this category, also.