Limiting reactant prob

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Limiting reactant prob
CHEMISTRY The Central Science 9th Edition
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?
David P. White
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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?
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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?
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Chapter 4 All about Aqueous Solutions

• 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)

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Models of dissolution (figure 4.3)
Ionic substance in water
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Molecularsubstance in H2O
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Ionization 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
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• 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

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Compounds in Solution
Ionic compounds are strong electrolytes Polyatomi
c 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.
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Picture of strong electrolyte
Strong acid HCl(g) H2O(l) H3O(aq)
A-(aq)
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Picture of weak electrolyte
Weak acid HA(aq) H2O(l)
H3O(aq) A-(aq)
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Soluble vs. electrolyte
Dont confuse solubility and strong vs. weak
electrolytes. Electrolyte means only that
substance exists as ions in water
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Precipitation reactions
Double replacement reaction ions switch Special
case of double replacement reactions also called
exchange or metathesis A solid (precipitate)
forms in these reactions ??How do we know what
the precipitate will be??
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Precipitation Reactions
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Solubility rules to remember
Soluble only means greater than 0.01 moles
dissolve in 1 L of solution

• All nitrates, acetates, ammonium and Group 1
  salts are soluble
• Solubility of chlorides, bromides and
  iodides(all soluble except Ag Pb2 and Hg22)
• Hydroxides (all insoluble except rule 1, Ca, Sr,
  Ba)
• What to know
• Sulfates mostly soluble
• Phosphates and carbonates (insoluble except rule
  1)

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Net 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
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Net ionic reactions

• 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)

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• Cross out spectators or ions on both sides of
  the arrow (lazy bums that dont 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)

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Steps to write net ionic equations

• Write a balanced complete equation.
• Dissociate any and only strong electrolytes.
• Cross out spectators.
• Whats left is the net ionic eq.

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• These forms of compounds do not make ions
• molecules
• weak electrolytes
• Water
• gases
• precipitates
• Keep together, they dont exist as ions in
  solution

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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?

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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
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Acids

• 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).

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Bases
Bases

• Bases form OH-, or react with acids (NH3,
  Drano, Milk of Magnesia).
• Metal hydroxides are strong basesBa(OH)2
  Ba2 2OH -

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Bases 2
Bases

• Some molecules, like amines, are weak bases.
• Weak bases ionize in water to make OH -

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Memorize strong acids and bases

• Memorize 7 strong acids
• HCl, HBr, HI H2SO4, HNO3, HClO3, HClO4
• OR
• Memorize the _________ common weak acids
• Soluble hydroxides are strong bases

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Reactions 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

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Concept check

• Which substance has the most ions form when
  dissolved in aqueous solution?
• NaC2H3O2
• K2CO3
• Na3PO4

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Concept 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
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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?
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Concentration for calculations
20.0 mL 0.0183 g/mL 0.366 g cobalt (II)
nitrate
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Concentration 2
Molarity, or number of moles per liter of solution
Molarity can be used like a conversion factor
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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
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To make a 250.0 mL solution of 1.00 molar NaCl
2. Dissolve in some water
4. M moles/L
14.58 g x 1 mol/58.54 g x 1/0.2500 L
1.000 mol/L
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0.20 L of 2.0 M solution 0.20 L x 2.0 mol/L
0.40 moles total
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
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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?
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Molarity, 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
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Molarity, moles/L
How many g of potassium sulfate are required to
make 235.0 mL of 0.152 M solution?
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Molarity, moles/L
How many g of potassium sulfate are required to
make 235.0 mL of 0.152 M solution?
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The mole highway
From mass To Moles With g/mole ratio or M
To mass With g/mole ratio or M From Moles
mole
mole
Use mole ratio from equation
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How many g of lead (II) iodide can be made by
mixing 25.0 mL of 0.230 M potassium iodide
with 25.0 mL of 0.140 M lead (II)
nitrate? Write molecular and net ionic
equations. Draw a mental model.
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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?
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pH is a measure of the acidity of a solution pH
is calculated as pH - log10H or H
10-pH What is pH of solution if H 1.3510-4
M? -log 0.000135 ______ (use 2 decimals) What
is H if pH 4.25? pH
scale
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Figure 16.5
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• auto-ionization of water

55.6 M Water treated like a molecule (very
few ions)
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Oxidation 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)
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Oxidation 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.

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Figure 4.13
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Activity 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.

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A copper strip in silver (I) nitrate solution
Time 0
Time 60 min
Which is more active, copper or silver? What is
the chemical reaction equation?
http//www.avon-chemistry.com/chem_intro_lecture.h
tml
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Zinc is higher than copper. Is zinc more
active? Will Cu2 ions oxidize Zn? Will Zn2 ions
oxidize Cu?
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http//imet.csus.edu/imet1/antares/folio/Teaching_
Units/echem/elec_04.gif
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Oxidation numbers

• Oxidation numbers
• A tool to judge whether a substance has been
  oxidized or reduced.
• Elements
• Monatomic ion
• Oxygen
• Hydrogen
• halogens

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Oxidation 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

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a castle in Westphalia, Germany, built in 1702
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Lincoln Castle, Lincolnshire, England
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Sulfate deposition LINK
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2.4 million tonnes
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14.8 million tons

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

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Pseudoephedrine HCl
Hydrochloride Citrate Sulfate Tartrate
sildenafil citrate
Oxycodone HCl
Glucosamine sulfate