Writing Reactions
--for unbalanced students
A few things to recall--
• Synthesis
• Decomposition
• Single replacement
• Double replacement
• Other redox
A+BAB
AB A+B
A+BC AC+B
Or
D+BC C+BD
AB+CD AD+BC
AB+CD a whole bunch of other
things.
A few things to recall--
• Metallic oxides and water make hydroxides
• M2O+H2O2MOH
• MO+H2OM(OH)2
• 2M2O3+3H2O 2M(OH)3
A few things to recall--
• Nonmetallic oxides and water make acids
• YO + H2O H2YO2
• YO2 + H2OH2YO3
• YO3 + H2OH2YO4
• 2Y2O5 + H2O2HYO3
A few things to recall--
• In a single replacement reaction—the more reactive element replaces the less reactive
• X +MYY +MX
means X is a more reactive nonmetal than Y
• A + BCB + AC
means A is a more reactive metal than B
A few things to recall--
• In a double replacement reaction, you need a molecule or a precipitate formed
• AB +CD AD + BC
if AD and BC are both soluble salts
A few things to recall--
• Carbonates decompose with heat or acid
A few things to recall--
• In a redox reaction, hydrogen ions and water can be reactants or products.
A few things to recall--
• In a redox reaction, you have to balance the charge as well
A few things to recall--
• Net ionic equations show dissociated ions, spectators are omitted
• AB +CD AD + BC, if AD is soluble,
• Write: B- +C+ BC
Predict the products
• AKA: Descriptive chemistry
• You are given to reactants. What products are formed? Go!
Predict the products
• Old Rules—– 8 sets, you choose 5– Don’t balance– Use a net ionic equation
• New rules– – Three sets, do all of them– Balance– Use a net ionic equation– Answer a question
Predict the products
• We will practice old rules first.
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
It will burn
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
Can only be
oxidized
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
Look for a precipitate
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride. Look for a precipitate
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride. Can be reduced
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride. Weak base
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
Can be reduced
What do you see?
• 1. A piece of solid bismuth is heated strongly in oxygen.• 2. A strip or copper metal is added to a concentrated
solution of sulfuric acid.• 3. Solutions of zinc sulfate and sodium phosphate are
mixed.• 4. Solutions of silver nitrate and lithium bromide are mixed.• 5. A stream of chlorine gas is passed through a solution of
cold dilute sodium hydroxide.• 6. Excess hydrochloric acid solution is added to a solution of
potassium sulfite.• 7. A solution of tin (II) chloride is added to an acidified
solution of potassium permanganate• 8. A solution of ammonium thiocyanate is added to a
solution of iron (III) chloride.
It’s complex
Arrhenius acids and bases
• Substances that ionize in water to form H+ ions are acids.
• Substances that ionize in water to form OH- ions are bases.
BrØnsted-Lowry Definition
• Substances that donate a proton (H+ ion) in a reaction are acids.
• Substances that accept a proton (H+ ion) are bases.
Lewis Definition
• Substances that accept an electron pair in a reaction are acids.
• Substances that donate an electron pair are bases.
Conjugates
• After an acid has donated a proton, the rest of the species is the conjugate base.
HAA- + H+
• After a base has accepted a proton, the resulting species is the conjugate acid.
B- + H+ HB
Please recall:
• Strong acids and bases dissociate completely in a water environment. Weak acids and bases do not.
• Strong acids= nitric, hydrochloric, sulfuric, hydrobromic, hydroiodic, perchloric
• Strong bases-Group 1 & 2 hydroxides—(group 2’s might not dissolve well)
We did not use:(but you still have to know)
These ions: Precipitate like:• MnO4
-, O2-2,CN- ,ClO4
- like NO3-
• F- like Cl-
• Mn+2,Fe+2 like Fe+3
• C2O4-2 like CO3
-2
• S-2 like OH-
• Hg2+2 like Ag+
• (oxides do not exist in a water solution!)
H+ + OH-H2O
• Just remember–
One H+ neutralizes one OH-
• It’s true for strong and weak acids and bases.
H+ + OH-H2O
• Just remember–
One H+ neutralizes one OH-
• It’s true for strong and weak acids and bases.
M1V1=M2V2
Moles of H+
Moles of OH-
A titration
• If 23.56 ml of a .115M NaOH solution neutralizes 10.00 ml of HCl solution, what is the concentration of the original acid?
Another titration
• If 14.78 ml of a .115M H2SO4 solution neutralizes 25.00 ml of NaOH solution, what is the concentration of the base?
Another titration
• If 14.78 ml of a .115M H2SO4 solution neutralizes 25.00 ml of NaOH solution, what is the concentration of the base?
Did you catch that?
Dilution
• Add more solvent to a solution, the concentration decreases.
M1V1=M2V2
Moles of
solute
Moles of
solute
A dilution
• If 150 ml of a .30 M NaOH solution is diluted to 250 ml, what is the new concentration of the base?
Another dilution
• What volume of solvent must be added to 100. ml of 1.5 M NaCl to make a solution that is .30 M [Cl-]?
Another dilution
• What volume of solvent must be added to 100. ml of 1.5 M NaCl to make a solution that is .30 M [Cl-]?
Did you catch that?
Not “to what new volume must it be diluted?”
“Life is pain, Your Highness.”
Wesley, from the Princess Bride by William Goldman
What is [Cl-]?
• 150 ml of .2 M NaCl,
• 250 ml of .4 M AlCl3• 200 ml of .35 M MgCl2 and
• 100 ml H20
--are mixed (assume volumes are additive, that is, Vfinal=700 ml)
What will happen…...if you add, to 1.0 L H2O at room
temperature, the following substances, in order:
5 g Na(s)5 g Mg(s) 5 g NaCl(s)
5 g Zn(C2H3O2)2(s)5 g HCl(g)
5 g H3PO4(l)