Writing Reactions --for unbalanced students. A few things to recall-- Synthesis Decomposition Single...

Writing Reactions

--for unbalanced students

A few things to recall--

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Other redox

AB A+B

A+BC AC+B

Or

D+BC C+BD

AB+CD AD+BC

AB+CD a whole bunch of other

things.


• Metallic oxides and water make hydroxides

• M2O+H2O2MOH

• MO+H2OM(OH)2

• 2M2O3+3H2O 2M(OH)3


• Nonmetallic oxides and water make acids

• YO + H2O H2YO2

• YO2 + H2OH2YO3

• YO3 + H2OH2YO4

• 2Y2O5 + H2O2HYO3


• 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


• 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


• Carbonates decompose with heat or acid


• In a redox reaction, hydrogen ions and water can be reactants or products.


• In a redox reaction, you have to balance the charge as well


• 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!


• 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


• 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?








It will burn

What do you see?








Can only be

oxidized

What do you see?








Look for a precipitate

What do you see?







solution of iron (III) chloride. Look for a precipitate

What do you see?







solution of iron (III) chloride. Can be reduced

What do you see?







solution of iron (III) chloride. Weak base

What do you see?








Can be reduced

What do you see?








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)

Writing Reactions --for unbalanced students. A few things to recall-- Synthesis Decomposition Single...

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