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.
To determine if a reaction will occur when two aqueous solutions are mixed, you need to examine the solubility rules and the likelihood of a reaction occurring.
First, let's consider the solubility rules:
1. Compounds containing alkali metals (Group 1A) cations (e.g., Li+, K+) and ammonium (NH4+) are soluble and will usually stay in solution.
2. Compounds containing nitrate (NO3-) and acetate (CH3COO-) are also usually soluble and will remain in solution.
3. Most chlorides (Cl-), bromides (Br-), and iodides (I-) are soluble, except for those containing silver (Ag+), lead (Pb2+), and mercury (Hg2+) ions.
4. Most sulfates (SO4 2-) are soluble, except for those containing calcium (Ca2+), strontium (Sr2+), barium (Ba2+), lead (Pb2+), and silver (Ag+) ions.
5. Carbonates (CO3 2-), phosphates (PO4 3-), sulfides (S 2-), and hydroxides (OH-) are often insoluble, except for those containing alkali metals (Group 1A) and ammonium (NH4+) ions.
Now let's consider each pair of solutions:
1. K2CO3 + HNO3:
- K2CO3 is a soluble salt according to rule 1.
- HNO3 is a soluble acid.
- The reaction between the salt and acid will produce carbonic acid (H2CO3), which is unstable and decomposes into water (H2O) and carbon dioxide (CO2).
- Therefore, a reaction will occur.
2. HCl + LiOH:
- HCl is soluble according to rule 3.
- LiOH is soluble according to rule 1.
- The reaction between the acid and base will produce water (H2O) and a salt, lithium chloride (LiCl).
- Therefore, a reaction will occur.
3. MgCl2 + KOH:
- MgCl2 is soluble according to rule 3.
- KOH is soluble according to rule 1.
- The reaction between the acid and base will produce water (H2O) and a salt, magnesium hydroxide (Mg(OH)2).
- Therefore, a reaction will occur.
4. Li2S + HCl:
- Li2S is soluble according to rule 1.
- HCl is soluble according to rule 3.
- The reaction between the salt and acid will produce hydrogen sulfide gas (H2S) and lithium chloride (LiCl).
- Therefore, a reaction will occur.
Therefore, the correct answer is "All of these solution pairs will produce reactions."
The pair of aqueous solutions that will react when mixed is:
HCl + LiOH
When hydrochloric acid (HCl) and lithium hydroxide (LiOH) are mixed, they undergo a neutralization reaction, producing water (H2O) and forming lithium chloride (LiCl).
The reactions for the other solution pairs are:
K2CO3 + HNO3: Potassium carbonate (K2CO3) will react with nitric acid (HNO3) to form water (H2O), carbon dioxide (CO2), and potassium nitrate (KNO3).
MgCl2 + KOH: Magnesium chloride (MgCl2) and potassium hydroxide (KOH) will not react when mixed. No reaction occurs between them.
Li2S + HCl: Lithium sulfide (Li2S) and hydrochloric acid (HCl) will react to form lithium chloride (LiCl) and hydrogen sulfide (H2S).
Therefore, the correct answer is option:
HCl + LiOH
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.
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html
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.