Limiting reactant probLimiting reactant prob

CHEMISTRY The Central Science

9th Edition

David P. White

Nitrogen monoxide can be prepared by the oxidation of ammonia by the following equation:

NH3 (g) + O2 (g) NO (g) + H2O (g)

If 45.7 g of NH3 and 52.5 g of O2 react

together, how many g of NO will be

formed?

If 18.59 mol of H2 is burned in air, what is the theoretical yield (in mol) of H2O?

If 7.50 mol H2O are formed, what is the percent yield?

If 18.59 mol of H2 is burned in air, what is the theoretical yield (in mol) of H2O?

H2 + O2 H2O

If 7.50 mol H2O are formed, what is the percent

yield?

Electrolytic Properties

• Water is a poor conductor of electricity• Aqueous solutions of ions can conduct electricity.• Three types of solutes:

• Strong electrolytes: (solute is all ions)• Weak electrolytes: (some ions, mostly molecules)• Non-electrolytes: (no ions, all molecules)

Chapter 4: Chapter 4: All about Aqueous SolutionsAll about Aqueous Solutions

Models of dissolution Models of dissolution (figure 4.3)(figure 4.3)Ionic substance in water

Molecularsubstance in H2O

Ionization vs. dissociationIonization vs. dissociation

Ions form in water in two ways

Dissociation: ionic substance dissociates (separates)

Ionization: molecular substance (no ions) reacts with water to form ions

Strong and Weak Electrolytes

• Strong electrolytes: Exist as 100% ions, conducts electricity

Nearly 100%

•Weak electrolytes: •make a small % of ions when dissolved.•ions in equilibrium with the molecule.•Can be very soluble, just not ionized

Compounds in SolutionCompounds in Solution

Ionic compounds are strong electrolytes

Polyatomic ions remain intact as ions when dissolving in water

Molecular compounds remain intact as moleculeswhen dissolving in water (non-electrolytes)

no ions in solution = nothing to transport electric charge.

Picture of strong electrolytePicture of strong electrolyte

Strong acid: HCl(g) + H2O(l) H3O+(aq) + A-(aq)

Picture of weak electrolytePicture of weak electrolyte

Weak acid: HA(aq) + H2O(l) H3O+(aq) + A-(aq)

Soluble vs. electrolyteSoluble vs. electrolyte

Don’t confuse solubility and strong vs. weak electrolytes.

Electrolyte means only that substance exists as ions in water

Ionic? Soluble? Electrolyte?

HCl

KOH

BaSO4 No

HC2H3O2 YES

Precipitation reactionsPrecipitation reactions

Double replacement reaction:

ions switch

Special case of double replacement reactionsalso called exchange or metathesis

A solid (precipitate) forms in these reactions

??How do we know what the precipitate will be??

Precipitation ReactionsPrecipitation Reactions

Solubility rules to rememberSolubility rules to remember

Soluble only means greater than 0.01 moles dissolve in 1 L of solution

1. All nitrates, acetates, ammonium and Group 1 salts are soluble

2. Solubility of chlorides, bromides and iodides(all soluble except Ag+ Pb2+ and Hg2

2+)

3. Hydroxides (all insoluble except rule 1, Ca, Sr, Ba)

4. What to know

• Sulfates mostly soluble

• Phosphates and carbonates (insoluble except rule 1)

Net Ionic reaction Concept checkNet Ionic reaction Concept check

Predict the products when NaOH (aq) is combined with HCl (aq), write a balanced chemical equation (including states of matter)

Write the total ionic equation

Write the net ionic equation

• Molecular equation (or “complete” equation): all species listed like molecules with full formulas:

HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)

total ionic equation: lists all ions:H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)

H2O(l) + Na+(aq) + Cl-(aq)

Net ionic reactionsNet ionic reactions

•Cross out “spectators” or ions on both sides of the arrow (lazy bums that don’t react)

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) H2O(l) + Na+(aq) + Cl-(aq)

•Net ionic equation: lists unique ions, only those that react:

H+(aq) + OH-(aq) H2O(l)

1. Write a balanced complete equation.

2. Dissociate any and only strong electrolytes.

3. Cross out spectators.

4. What’s left is the net ionic eq.

Steps to write net ionic equations:

These forms of compounds do not make ionsmoleculesweak electrolytesWatergases precipitates

Keep together, they don’t exist as ions in solution

Concept check:Concept check:

What is the complete equation?

NiCl2(aq) + 2AgNO3(aq) 2AgCl(s) + Ni(NO3)2(aq)

What is the total ionic equation?

What is the net ionic equation?

A solution of lead (II) nitrate is mixed with a solution of sodium chloride.

Write the balanced chemical equation, the total ionic equation, and the net ionic equation for the reaction

• Acid = substance that ionizes to form H+ in solution (HCl, HNO3, CH3CO2H, citric, vitamin C).

H+ also written as H3O+ (hydronium)

• one acidic proton= _______________(HC2H3O2).

• two acidic protons = _______________

(H2SO4).

AcidsAcids

• Bases = form OH-, or react with acids (NH3, Drano™, Milk of Magnesia™).

• Metal hydroxides are strong bases:Ba(OH)2 Ba2+ + 2OH -

BasesBasesBasesBases

• Some molecules, like amines, are weak bases.

• Weak bases ionize in water to make OH -

BasesBasesBases 2Bases 2

•Memorize 7 strong acids:

HCl, HBr, HI H2SO4, HNO3, HClO3, HClO4

OR

Memorize the _________ common weak acids

•Soluble hydroxides are strong bases

Memorize strong acids and basesMemorize strong acids and bases

Reactions of acids and basesReactions of acids and bases

•Neutralization: acid + base are mixed:

HNO3(aq) + KOH(aq) ???

•Salt = ionic compound cation from base anion from acid.

•Neutralization of acid with metal hydroxide produces water and a salt.•Acids + carbonates = CO2 and H2O

Concept checkConcept check

Which substance has the most ions form when dissolved in aqueous solution?

1. NaC2H3O2

2. K2CO3

3. Na3PO4

Concept checkConcept check

Classify each of the following as a strong (1), weak (2) or non-electrolyte (3)

When dissolved in water:

NaCl

(NH4)2CO3

C12H22O11

HF (weak acid)

CH3OH

Concept check:Concept check:

A solution of nickel (II) chloride is mixed with a solution of silver nitrate, a ppt forms.

What is the complete equation?

What is the total ionic equation?

What is the net ionic equation?

Concentration for calculationsConcentration for calculations

20.0 mL * 0.0183 g/mL = 0.366 g cobalt (II) nitrate

Concentration 2Concentration 2

Molarity, or number of moles per liter of solution

Volume of solution (liters)

Molarity = moles of solute = M

Molarity can be used like a conversion factor

A 1.0 M (molar) NaCl solution has 1.0 mol or 58.5 g of NaCl dissolved in water to make 1.0 L

Volume x moles = moles

L

Moles x L = volume (L)moles

To make a 250.0 mL solution of 1.00 molar NaCl

4. M = moles/L

1. Measure mass

14.58 g

3. Fill volumetric flask to known volume

0.2500 L

2. Dissolve in some water

14.58 g x 1 mol/58.54 g x 1/0.2500 L = 1.000 mol/L

Pour ½ in each beaker

in each beaker:

0.10 L of 2.0 M solution:

0.10 L x 2.0 mol/L = 0.20 moles

Same conc, fewer particles

0.20 L of 2.0 M solution:

0.20 L x 2.0 mol/L = 0.40 moles total

Pour 0.10 L H2O into beaker

0.10 L of solution + 0.10 L H2O = 0.20 L

0.10 L x 2.00 mol/L = ______________

0.20 moles = _____ 0.20 L new solution

Same # of moles, but more dilute

What is molarity if 0.450 mol of NaCl is dissolved to make 0.3500 L of solution?

What is molar concentration when 3.18 g of NaNO3

is dissolved to make 150.0 mL of solution?

Molarity, moles/LMolarity, moles/L

What is molar concentration when 3.18 g of NaNO3 is dissolved to make 150.0 mL of

solution?

3.18 g NaNO3 x 1 mol/84.99g = 0.0374 mol

0.0374 mol/0.1500L =

Molarity, moles/LMolarity, moles/L

How many g of potassium sulfate are required to make 235.0 mL of 0.152 M solution?

Molarity, moles/LMolarity, moles/L

How many g of potassium sulfate are required to make 235.0 mL of 0.152 M solution?

molemole

Use mole ratio from equation

From mass To MolesWith g/mole ratio or M

To massWith g/mole ratio or MFrom Moles

The mole highwayThe mole highway

How many g of lead (II) iodide can be made by mixing

25.0 mL of 0.230 M potassium iodide with25.0 mL of 0.140 M lead (II) nitrate?

Write molecular and net ionic equations.

Draw a mental model.

0.879 M H2SO4 is added to 45.0 mL of 0.100 M NaOH, until the acid is just completely neutralized.

How many mL of H2SO4 were added?

pH is a measure of the acidity of a solution

pH is calculated as pH = - log10[H+]

or [H+] = 10-pH

What is pH of solution if [H+] = 1.35*10-4 M?

-log 0.000135 = ______ (use 2 decimals)

What is [H+] if pH = 4.25?

pH scale

Figure 16.5

• “auto-ionization” of water

H2O(l) + H2O(l) H3O+(aq) + OH−(aq)

55.6 MWater treated like a molecule (very few ions)

Oxidation and reductionOxidation and reduction

Some reactions are a transfer of e-

Mg(s) +2HCl(aq) MgCl2(aq) + H2(g)

Write net ionic equation:

Mg(s) +2H+(aq) Mg2+(aq) + H2(g)

Oxidation and reductionOxidation and reduction

Mg(s) +2H+(aq) Mg2+(aq) + H2(g)

• In the above rxn, Mg(s) loses e-, H+ gains e-

• Oxidized: atom, molecule, or ion becomes more positively charged.

• Reduced: atom, molecule, or ion becomes less positively charged.

Figure 4.13Figure 4.13

Activity seriesActivity series

• Some metals are easily oxidized (lose e–), others are not.

• Activity series: list of metals in decreasing ease of oxidation.

• Metals higher on the activity series are more active lose e– more easily.

• Any metal can be oxidized by the ions of elements below it.

Which is more active, copper or silver?What is the chemical reaction equation?

A copper strip in silver (I) nitrate solution

Time = 0 Time = 60 min

http://www.avon-chemistry.com/chem_intro_lecture.html

Zinc is higher than copper.

Is zinc more active?

Will Cu2+ ions oxidize Zn?

Will Zn2+ ions oxidize Cu?

http://imet.csus.edu/imet1/antares/folio/Teaching_Units/echem/elec_04.gif

Oxidation numbersOxidation numbers

• Oxidation numbers:• A tool to judge whether a substance has been

oxidized or reduced.– Elements– Monatomic ion– Oxygen– Hydrogen– halogens

Oxidation reationsOxidation reations• What elements are oxidized or reduced

CH4 + 2O2 CO2 + 2H2O

Fe2O3 + 3CO 2Fe + 3CO2

Br2 + 2NaI 2NaBr + I2

Cu(OH)2 + 2HNO3 Cu(NO3)2 + 2H2O

                                                         a castle in Westphalia, Germany, built in 1702

Lincoln Castle, Lincolnshire, England

http://water.usgs.gov/nwc/NWC/pH/img/usphst5.imf

Sulfate deposition LINK

2.4 million tonnes

14.8 million tons

SOx from coal, (some from oil) NOx from cars

Pseudoephedrine HCl

Glucosamine sulfate

HydrochlorideCitrateSulfateTartrate

Oxycodone HCl

sildenafil citrate