Chemistry lab

Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
Mixing Aqueous Solutions of Two Ionic Compounds
Aqueous solutions of ionic compounds are made by mixing soluble ionic compounds into water. When an ionic
compound dissolves in water, it breaks down into its component ions. For example, when NaCl dissolves in water
what is REALLY in the solution are the ions Na+ and Cl- surrounded by water molecules.
When mixing aqueous solutions together, think about what is REALLY being mixed: the aqueous ions. A reaction occurs
ONLY if one or more of the possible products if these ions come together is a solid, liquid or gas. A product is a solid
if it is insoluble (not soluble) in water. For this exercise, evidence that a reaction occurs is the formation of a solid
product. If all of the possible products of the reaction are soluble, no reaction occurs.
If aqueous lithium phosphate (Li3PO4(s)) and aqueous magnesium nitrate (Mg(NO3)2(s)) are mixed, start with the
solid form of the compounds and dissolve them in water:
Li3PO4(s) → 3 Li+(aq) + PO43-(aq)
Mg(NO3)2(s) → Mg2+(aq) + 2 NO3-(aq)
(Li3+ and Li33+ are not correct ions)
((NO3)2- is not a correct ion)
Next, determine the possible products. Consider what happens if:
• Lithium ion (Li+) and nitrate ion (NO3-) come together; and
• Magnesium ion (Mg2+) and phosphate ion (NO3-) come together.
Since magnesium ion has a 2+ charge and phosphate ion has a 3- charge, the compound needs 3 Mg2+ ions and 2
PO43- ions to form a neutral compound. To get that number of ions, the first equation must be multiplied by 2 and the
second must be multiplied by 3 to yield:
2 Li3PO4(s) → 6 Li+(aq) + 2 PO43-(aq)
3 Mg(NO3)2(s) → 3 Mg2+(aq) + 6 NO3-(aq)
The possible products are: LiNO3 and Mg3(PO4)2
If a reaction occurred, one or more of the products must be a solid, liquid and/or a gas.
Both of the possible products are ionic compounds, so they cannot be liquid or gas at room temperature. Since the
environment is water, compare each compound to the solubility rules (below) for compounds in water:
• LiNO3 is soluble in water, no solid forms in the aqueous solution;
• Mg3(PO4)2 is not soluble in water, a solid forms in the aqueous solution.
Thus, because a solid formed, a reaction did occur.
For this exercise:
STEP 1: Make sure the equation is correctly-balanced and do not forget to include the states of matter (s, l, g, aq).
Write the molecular equation for the reaction:
2 Li3PO4(aq) + 3 Mg(NO3)2(aq) → Mg3(PO4)2(s) + 6 LiNO3(aq)
Page 1
Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
STEP 2: Since a solid formed, a reaction DID occur. Write yes.
STEP 3: Write the complete ionic equation. This equation shows what ions are being mixed together, what
product(s) formed and what ions remain. Make sure the equation is correctly-balanced and do not forget to include
the states of matter (s, l, g, aq). Write:
6 Li+(aq) + 2 PO43-(aq) + 3 Mg2+(aq) + 6 NO3-(aq) → Mg3(PO4)2(s) + 6 Li+(aq) + 6 NO3-(aq)
STEP 4: Identify the spectator ions. These are the ionic species that do not participate in the formation of the
product. Look for the ionic species that are the same on both the reactants and products sides of the reaction. In
this reaction the spectator ions are Li+ and NO3-. Write:
Li+(aq) and NO3-(aq)
STEP 5: The net ionic equation represents the actual formation of the product. Start with the complete ionic
equation, subtract the spectator ions, to yield the net ionic equation. Make sure the equation is correctly-balanced
and do not forget to include the states of matter (s, l, g, aq). Write:
2 PO43-(aq) + 3 Mg2+(aq) → Mg3(PO4)2(s)
STEP 6: The systematic name for the product. Write:
Magnesium phosphate
Page 2
Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
Fill in the table below:
• For each set of aqueous solutions being mixed, write the correct form of the ions being mixed.
Circle the ions that form an insoluble product — only if one forms; and
• Write the formula of the insoluble salt — only if one forms.
Reaction
1
Compounds in Mixture
CaCl2 + Na2CO3
2
AgNO3 + NaCl
3
LiNO3 + Na2SO4
4
BaBr2 + Li3PO4
5
MgCl2 + NaOH
6
SrI2 + Cs2CO3
7
Li2CrO4 + MgBr2
8
NH4NO3 + Na3PO4
Ions in Mixture
Ca2+
Cl-
Na+
CO32-
Formula of Insoluble Salt (if any)
On the following pages:
For each combination of solutions in the above table, write the correctly balanced molecular
equation. Compare possible products with the Solubility Rules. Did a reaction occur? Write
yes or no. If a solid product did not form, go on to the next set of solutions.
If a reaction did occur, continue through the following steps:
1. Write the correctly-balanced complete ionic equation;
2. Write the formulas for the spectator ions;
3. Write the correctly-balanced net ionic equation.
4. Write the systematic name of the ONE product formed.
In every reaction equation, include all of the states of matter (s, l, g, aq).
Page 3
Name: ____________________________
Date: _______________________
Reaction 1
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Reaction 2
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Page 4
Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
Reaction 3
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Reaction 4
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Page 5
Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
Reaction 5
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Reaction 6
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Page 6
Soluble and Insoluble Salts
Name: ____________________________
Date: _______________________
Reaction 7
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Reaction 8
Write the BALANCED Molecular Equation
Did a reaction occur? (Yes or No)
1. ONLY if so, write the BALANCED complete ionic equation
2. Write the formulas for the spectator ions
3. Write the BALANCED net ionic equation
4. Write the systematic name for the product
Page 7
Soluble and Insoluble Salts