Chem 20 Solutions 3 & 4
Chemical reactions/entities in Solution
When substances dissolve, they become individual ions (if ionic) or individual
molecules (if molecular).
Turn water into wine, milk, beer experiment
Follow the instructions on the handout and demo for the class.
Hints:
The wine is created by phenolphthalein indicator turning red in a base
The milk is created by a precipitate.
The concentrated hydrochloric acid in the fumehood is very dangerous. Use
goggles! A watchglass must be used to cover the fumes.
Review the rules for listing entities before answering the following questions.
Questions:
1. What is the name of the precipitate that caused the milk?
2. Why did the final glass have a yellow color (what indicator was responsible)?
Listing Entities in Solution and predicting reactions
1. First, you must classify the type of compound as ionic, molecular, acid or metal
a) Ionic: contains a metal. Exception: NH4 (polyatomic ion) compounds
eg. CaCl2, Mg3(PO4)2, NH4NO3 , Ba(OH)2
_____________________________________________________________
b) Molecular: Contains no metals. Remember, H acts like a metal but is not a
true metal.
eg. C2H5OH, SO2, Cl2, H2O2
_____________________________________________________________
c) Acid: Formulas can be of two types:
H____(aq) or _____COOH(aq)
eg. HNO3(aq) or CH3COOH(aq)
_____________________________________________________________
d) Metal: Monoatomic metal formula
eg. Fe, Cu, Mg, Ca
p 202 #8 , and p 41 #24 (Classify the type of substance present and
give the formula or name)
2. Next, follow the rules for each compound type:
a) Ionic:
Charged water molecules pull apart ions from soluble ionic compounds (solute):
http://www.youtube.com/watch?v=EBfGcTAJF4o&feature=related
Soluble ionic compounds dissociate into ions. Therefore ions are listed.
eg. NaCl… Na+(aq) , Cl-(aq) , H2O(l)
Al2(SO4)3 (aq) …. Al3+(aq) SO42- (aq) , H2O(l)
Ba(OH)2….. Ba2+(aq), OH-(aq) , H2O(l)
Low soluble ionic compounds do not dissociate to any great degree
eg. AgCl…. AgCl(s) , H2O(l)
_____________________________________________________________
b) Molecular:
Soluble molecular compounds are aqueous, but don’t dissociate into ions
eg. C6H12O6…. C6H12O6 (aq) , H2O(l)
Insoluble molecular compounds remain in the state they were in
eg. C8H18 (l)…. C8H18 (l) , H2O(l)
_____________________________________________________________
c) Acid:
Strong acids ionize 100%
eg. HCl(aq)…. H+(aq) , Cl-(aq) , H2O(l)
HNO3(aq)….. H+(aq) , NO3 -(aq) , H2O(l)
Weak acids remain mainly in molecular form and do not ionize to any great
degree
eg. CH3COOH(aq) …. CH3COOH(aq) , H2O(l)
_____________________________________________________________
d) Metal :
Remain as solid metals
eg. Fe…. Fe(s) , H2O(l)
----------------------p. 202 Lab ex 5B, 1-3, 8 (list entities and write dissociation/ionization equations
for each compound), p 41 #24 (list entities and write dissociation/ionization
equations for each compound)