|
1
|
|
|
2
|
- Concepts:
- coefficient, balanced chemical reaction, ion exchange reaction, net
ionic reaction, spectator ion(s)
- solubility rules, soluble, insoluble, strong acid, weak acid,
monoprotic acid, diprotic acid, polyprotic acid, organic acid,
inorganic acid
- Skills:
- Know what acids decompose into a gas and water
- Know and be able to write equations for the general reactions of acids
with metals, oxides, hydroxides, carbonates, hydrogencarbonates,
sulfites and sulfides
- Know and use strong and weak acids in ion exchange reactions
- Be able to identify substances as either strong electrolyte or weak
electrolyte or nonelectrolyte
|
|
3
|
- 1. Combination/Synthesis
- Combination reactions are ones where the reactants are two different
elements or an element and a compound or two compounds which combine to
produce a single compound.
- Element A + Element B à
Single Compound containing A and B
- A metal and a non-metal can combine to form an ionic compound or two
non-metals can combine to form a covalent compound.
- Two metals cannot combine to form compounds however. (They do mix to
give alloys, which is a mixture and not a compound however.)
- Or
- Element A + Compound BC à
Single Compound containing A, B & C elements
- Or
- Compound AB + Compound CD à Single Compound containing A, B, C & D elements
- Sometimes these reactions are also referred to as a synthesis reaction.
|
|
4
|
- 2. Combustion
- Combustion reaction is reaction between a substance (element or
compound) and oxygen.
- This is essentially the reaction that takes place when a substance burns
in air.
- Combustion reaction is the source of most of the energy we use.
- Combustion of natural gas (methane) is the reaction that release heat
energy used in cooking food.
- Combustion of petrol is the reaction that take place in the engine of a
motor vehicle the energy evolved driving it.
- The product(s) of combustion of an element is always the oxide of the
element.
- Mg(s) + O2(g) à MgO(s)
- S(s) + O2(g) à
SO2(g)
- C(s) + O2(g) à
CO2(g)
- N2(g) + O2(g) à NO(g)
|
|
5
|
- H2(g) + O2(g) à H2O(l) (the oxide of hydrogen)
- Notice that the reaction between an element and oxygen can be classified
as both combination and combustion.
- When a compound burns the oxides of the elements that make up the
compound are formed.
- When you burned methane in the lab, for instance, the products formed
are carbon dioxide and water.
- The reason those two oxides are formed is because methane is made up of
carbon and hydrogen.
- CH4(g) + O2(g) à CO2 + H2O(l)
- 3. Ion-exchange/double displacement
(replacement)/metathesis/precipitation reaction
- Salt solution 1 + salt solution 2 à precipitate of insoluble salt + solution of other salt
- As you know by now, for the above reaction to occur, one of the
products has to be insoluble.
|
|
6
|
- 4. Next we will look at firstly a variety of reactions involving acids,
namely:
- i) Metal-acid—displacement reactions
- ii) Metal oxide-acid
- iii) Metal hydroxide-acid—neutralization reaction (acid base reaction)
- iv) Carbonate-, hydrogencarbonate-, sulfite-, hydrogensulfite-,
sulfide-acid
- 5. And also at Oxide hydration reactions
|
|
7
|
- Acids (according to Arrhenius definition) are compounds that produce
hydrogen ions in solution.
|
|
8
|
- Classification by type: inorganic
(HCl, HBr, H2SO4) and organic (CH3COOH).
- Classification by composition: binary (HCl, HBr) and oxyacids (H2SO4,
HNO3, HClO4, H2CO3).
- Classification by strength: Strong (HCl, HBr, H2SO4)
and weak (H2S, H2CO3, CH3COOH).
- Classification by the number of hydrogen in it: monoprotic (HBr, HNO3,
HClO4, CH3COOH), diprotic (H2SO4,
H2CO3) and
polyprotic (H3PO4).
|
|
9
|
- Many oxides of non-metals when dissolved in water produce acids. The
oxides of non-metals, the starting materials for inorganic acids are
referred to as acid anhydrides (anhydride = “without water”).
- Acid anhydrides produce acids (oxacids) when dissolved in water
(hydrated).
- Most oxacids have a corresponding acid anhydride. The following
equations show some selected acid anhydrides undergoing hydration to
produce their corresponding acid.
- SO2 (g) + H2O (l) ® H2SO3 (aq) SO3 (g) + H2O
(l) ® H2SO4
(aq)
- N2O5 (g) + H2O (l) ® 2HNO3 (aq) N2O3
(g) + H2O (l) ® 2HNO2 (aq)
- P2O5 (s) + 3H2O (l) ® 2H3PO4 (aq) P2O3
(s) + 3H2O (l) ® 2H3PO3 (aq)
- CO2 (g) + H2O (l) ® H2CO3 (aq)
|
|
10
|
- For now, bases are hydroxides of metals. Later we will refine this
definition further.
- Some of the hydroxides dissolve in water (called alkalis) to produce
hydroxides ion, while others are insoluble but react with acids to
produce salt and water.
- The term anhydride also applies to bases. All oxides of metals are
referred to as base anhydrides.
- Just as many acid anhydrides undergo hydration to produce their
corresponding acid, group IA oxides, and only these, undergo hydration
to produce their corresponding base.
- M2O (s) + H2O (l) ® 2MOH (aq)
- Where, M = group IA metal. For example:
- Na2O (s) + H2O (l) ® 2NaOH (aq)
- K2O (s) + H2O (l) ® 2KOH (aq)
|
|
11
|
- Strong acids are acids that dissociate (ionize) completely in water,
while weak acids are acids that either do not undergo dissociation at
all or undergo only partial dissociation.
- The strong acids you need to know are: HCl (aq), HBr (aq),
HI (aq), H2SO4 (aq), HNO3 (aq),
HClO4 (aq)
- Example of some weak acids are: HF (aq), H2S
(aq), H2CO3 (aq), H2SO3 (aq),
CH3COOH(aq). (You will add more to this list.)
- What does complete and partial dissociation mean?
- HB(s l or g)
H+(aq) + B–(aq)
- Complete dissociation means that all of HB will ionize into the hydrogen
ions and the anion.
- One mol of the acid HB will produce in 1 mol each of H+(aq)
and B–(aq) ions in the solution.
|
|
12
|
- A strong acid HA (left) is completely ionized in water. A weak acid HB
(right) exists mostly as undissociated HB molecules in water. Note that
the water molecules are not shown in this figure.
- Examples:
- HCl(aq) is completely ionized.
- Ethanoic acid (CH3COOH) exists in water mostly as
undissociated molecules. Only a small percentage of the molecules are
ionized.
|
|
13
|
- HB(s l or g) H+(aq)
+ B–(aq)
- Partial dissociation means that if 1 mol of the acid is dissolved in
water, some molecules of HB will remain intact, and so less than 1 mol
each of H+(aq) and
B–(aq) ions result (see previous slide).
- Another way of putting it is to say that a 1M solution of strong acid
such HCl will produce a solution that is 1molar in concentration of both
H+ and Cl– ions.
- But 1M solution of ethanoic acid (CH3COOH) will contain some
undissociated (unionized) CH3COOH molecules, and therefore
will be less than 1 mol dm–3 of each of H+
and CH3COO– (ethanoate) ions.
|
|
14
|
- Similarly, strong bases are bases that dissociates completely in water
just like strong acids.
- For now, bases are hydroxides of metals. Later we will refine this
definition further.
- All hydroxides of Group IA metals and Ca, Sr, and Ba are strong bases.
- They dissolve in water to produce hydroxide ions.
- These are referred to as alkalis.
- Other metal hydroxides are insoluble but react with acids to produce
salt and water
|
|
15
|
- Weak bases do not dissociate completely.
- Ammonia is a weak base.
- Aqueous ammonia is a solution of ammonia which reacts with water and
forms ammonium and hydroxide ions only to some degree.
- NH3 (aq) + H2O (l) l NH4+ (aq) + OH –(aq)
|
|
16
|
|
|
17
|
- Because strong acids undergo complete dissociation, they are better
conductors of electricity in solution than weak acids, they are stronger
electrolytes than weak acids.
- An electrolyte is a compound which in solution conducts electricity.
- Free floating ions are responsible for conduction of electricity by a
solution.
- Equal concentrations of strong and weak acids, because of the different
degree of dissociation, contain different concentration of ions—a strong
acid contains higher concentration of ions leading to better
conductivity.
- Similarly, bases (hydroxides) which dissolve in water (all hydroxides of
Group IA metals and Ca, Sr, and Ba) are strong electrolytes.
|
|
18
|
- (a) strong electrolyte, therefore strong conduction (b) weak
electrolyte therefore weak conduction
(c) non-electrolyte therefore no conductivity
|
|
19
|
- So, in general all strong acids, strong bases and soluble ionic
compounds are strong electrolytes.
- Weak acids and bases are weakly conducting, and therefore weak
electrolytes.
- Molecular compounds (such as CO, O2, C6H12O6)
that don’t produce ions in aqueous solution are nonelectrolytes.
|
|
20
|
- I. Reactions with metals—if they react with a metal, they produce salt
and hydrogen gas.
- General form of the molecular equation and examples:
- Metal(s) + Acid (aq) ® Salt (aq) + H2 (g)
- Strong acid: Zn (s) + 2 HCl (aq) ® ZnCl2 (aq) + H2
(g)
- Weak acid: Zn (s) + 2 CH3COOH (aq) ® Zn(CH3COO)2 (aq)
+ H2 (g)
- Full ionic equations:
- Strong acid: Zn (s) + 2 H+ (aq) + 2
Cl- (aq)
® Zn2+ (aq)
+ 2 Cl- (aq)
+ H2 (g)
- Weak acid: Zn (s) + 2 CH3COOH (aq) ® Zn2+ (aq)
+ 2 CH3COO- (aq) + H2 (g)
- General forms of the net-ionic equation and examples:
- Strong acid: Metal (s) + H+ (aq) ® Metal ion (aq)
+ H2 (g)
- Eg. Zn(s) + 2H+ (aq) ® Zn2+ (aq)
+ H2 (g)
- Weak acid: Metal (s) + HB (aq) ® Metal ion (aq)
+ B- (aq)
+ H2 (g)
- Eg. Zn(s) + CH3COOH (aq) ® Zn2+ (aq)
+ 2 CH3COO- (aq) + H2 (g)
|
|
21
|
- II. Reactions with solid metal oxides—they produce salt and water.
- General form of the molecular equation:
- Metal oxide (s) + Acid (aq) ® Salt (aq) + H2O (l)
- Strong acid: Na2O (s) + H2SO4 (aq)
® Na2SO4
(aq) + H2O (l)
- Weak acid: Na2O (s) + 2CH3COOH (aq)
® 2NaCH3COO (aq)
+ H2O (l)
- Full ionic equations:
- Strong acid: Na2O (s) + H+ (aq)
+ SO42- (aq) ® 2Na+ (aq)
+ SO42- (aq) + H2O (l)
- Weak acid: Na2O (s) + CH3COOH (aq)
® Na+ (aq)
+ CH3COO-(aq) + H2O (l)
- General form of the net-ionic equation and examples:
- Strong acid: Metal oxide (s) + H+ (aq)
® Metal ion (aq)
+ H2O (l)
- Eg. Na2O (s) + H+ (aq) ® 2 Na+(aq) +
H2O (l)
- Weak acid: Metal oxide (s) + HB (aq) ® Salt (aq) + H2O
(l)
- Eg. Na2O (s) + CH3COOH (aq)
® 2Na+ (aq)
+ 2 CH3COO- (aq) + H2O (l)
|
|
22
|
- III. Reactions with aqueous and solid hydroxides—results in salt and
water
- Aqueous hydroxides: General form of molecular equation and example:
- Metal hydroxide (aq) + Acid (aq) ® Salt (aq) + H2O
(l)
- E.g. NaOH (aq)
+ H2SO4 (aq)
® Na2SO4
(aq) + H2O (l)
- Full ionic equation:
- E.g. Na+ (aq) + OH- (aq) + H+ (aq) + SO42- (aq) ® Na+ (aq)
+ SO42- (aq) + H2O (l)
- General form of net-ionic equation and example:
- Strong acid: Metal hydroxide (s) + H+ (aq)
® Metal ion (aq)
+ H2O (l)
- E.g. OH- (aq)
+ H+ (aq) ® H2O (l)
- How do the equations change if a weak acid is used? And how does the
equations for reactions involving a solid hydroxide vary?
- Check previous examples or the next couple of slides.
|
|
23
|
- IV. Reactions with solid carbonates, hydrogencarbonates, sulfites,
hydrogen sulfites—reaction where a weak acid is produced.
- In this type of reactions, the weak acid products either are unstable
and dissociate into a gas and water (as in the case of carbonates,
hydrogen carbonates, sulfites and hydrogensulfites) or is liberated as
gas (as in the case of sulfides).
- General forms of molecular equations for reactions with carbonates and
hydrogen carbonates:
- Metal carbonate (s or aq) + Acid (aq) ® Salt (aq) + H2CO3
(aq)
- But, carbonic acid is unstable and will dissociates spontaneously.
- H2CO3 (aq) ® CO2 (g) + H2O (l)
- \ Metal carbonate (s
or aq) + Acid (aq) ® Salt (aq) + CO2 (g) + H2O
(l)
- Similarly,
- Metal hydrogencarbonate (s) + Acid (aq) ® Salt (aq) + H2CO3
(aq)
- But, H2CO3 (aq) ® CO2 (g) + H2O (l)
- \ Metal hydrogencarbonate (s
or aq) + Acid (aq) ® Salt (aq) + CO2 (g) + H2O
(l)
|
|
24
|
- Reaction with carbonate
- Na2CO3 (s) + 2HCl (aq) ® 2NaCl (aq) + CO2
(g) + H2O (l)
- Full ionic equation:
- 2Na+ (aq) + CO32 -(aq) + 2H+
(aq) + 2Cl- (aq) ® 2Na+ (aq)
+ 2Cl- (aq)
+ CO2 (g) + H2O (l)
- Net Ionic equation
- CO32 -(aq) + 2H+ (aq) ® CO2 (g) + H2O
(l)
- Reaction with hydrogencarbonate
- NaHCO3 (s) + HCl (aq) ® NaCl (aq) + CO2 (g) + H2O
(l)
- Full ionic equation:
- 2Na+ (aq) + HCO3 -(aq) + H+
(aq) + Cl- (aq) ® Na+ (aq) +
Cl- (aq)
+ CO2 (g) + H2O (l)
- Net Ionic equation
- HCO32 -(aq) + H+ (aq) ® CO2 (g) + H2O
(l)
- How would the equations vary if a weak acid were used?
|
|
25
|
- General forms of molecular equation:
- Metal sulfite (s or aq) + Acid (aq) ® Salt (aq) + H2SO2
(aq)
- But, sulfurous acid is also unstable just like carbonic acid and will
spontaneously dissociate.
- H2SO3 (aq) ® SO2 (g) + H2O (l)
- \ Metal sulfite (s or
aq) + Acid (aq) ® Salt (aq) + SO2 (g) + H2O
(l)
- Similarly,
- Metal hydrogensulfite (s) + Acid (aq) ® Salt (aq) + H2SO3
(aq)
- But, H2SO3 (aq) ® SO2 (g) + H2O (l)
- \ Metal hydrogensulfite (s
or aq) + Acid (aq) ® Salt (aq) + SO2 (g) + H2O
(l)
- How would the full and net ionic equation look like?
- How are they different if the salt is in solution as opposed to being in
the solid state?
- How do they vary when a weak acid is used?
|
|
26
|
- General forms of molecular equation:
- Metal sulfide (s or aq) + Acid (aq) ® Salt (aq) + H2S
(g)
- Because hydrogen sulfide is a weak acid, it does not dissolve or
dissociate into hydrogen ion and HS– to any appreciable
extent.
- What would full and net ionic equations look like?
|
|
27
|
- The general form of the reactions considered so far:
- Ion-exchange reaction:
- Reactant salt 1(aq) + Reactant salt 2(aq) ® Product salt 1(s) +
Product salt 2(aq)
- NB: If neither of the products is insoluble, then there is no reaction.
- Anhydride hydration:
- Base anhydride(s) + H2O (l) ® Metal hydroxide (aq)
- NB: Applicable only to Group I oxides.
- Acid anhydride (g or s) + H2O (l) ® Acid (aq)
|
|
28
|
- Reactions of acids:
- Metal(s) + Acid (aq) ® Salt (aq) + H2 (g) NB: Not ALL
metals react with acids.
- Metal oxide (s) + Acid (aq) ® Salt (aq) + H2O (l)
- NB: You can’t have a solution of a metal oxide; if the oxide dissolves,
it produces a hydroxide!
- Metal hydroxide (s or aq) + Acid (aq) ® Salt (aq) + H2O
(l)
- Metal carbonate (s or aq) + Acid (aq) ® Salt (aq) + CO2
(g) + H2O (l)
- Metal hydrogencarbonate (s or aq) + Acid (aq) ® Salt (aq) + CO2
(g) + H2O (l)
- Metal sulfite (s or aq) + Acid (aq) ® Salt (aq) + SO2
(g) + H2O (l)
- Metal hydrogensulfite (s or aq) + Acid (aq) ® Salt (aq) + SO2
(g) + H2O (l)
- Metal sulfide (s or aq) + Acid (aq) ® Salt (aq) + H2S
(g)
|
|
29
|
- The difference between molecular and full ionic equations:
- In the full ionic equation, strong electrolytes (salt solutions,
strong acids and strong bases) appear in their dissociated (aqueous ionic)
form. All other reagents are the same in both equations.
- The difference between full ionic and net ionic equations:
- The spectator ions in the full ionic equation—the aqueous ions that
remain aqueous at the end of the reaction—do not appear in the net
ionic equation.
|
|
30
|
- 1. Combination/Synthesis
- 2. Combustion
- 3. Ion-exchange/double displacement (replacement)/metathesis
- 4. Acid reactions
- i). Acid-metal reactions
- Metal + Acid à Salt +
Hydrogen
- ii). Metal oxide-acid reaction
- Metal oxide + Acid à
salt + water
- iii). Metal hydroxide-acid (neutralization) reaction
- Metal hydroxide + Acid à
salt + water
- iv). Carbonate-, hydrogencarbonate-, sulfite-, hydrogensulfite-
sulfide-, acid reactions
- Metal carbonate (hydrogencarbonate) + Acid à salt + water + carbon dioxide
|
|
31
|
- Metal sulfite (hydrogensulfite) + Acid à salt + water + sulfur dioxide
- Metal sulfide + Acid à
salt + water + hydrogen sulfide
- 5. Acid and base anhydride hydration reaction
- When soluble oxides of a metal or a non-metal reacts with water, the
product is either an alkali or an acid.
- Metal oxide + water à
alkali
- Non-metal oxide + water à
Acid
- 6. The next reaction we will consider: Redox.
|
|
32
|
- 1. Consider two separate aqueous solutions: one of a weak acid HA and
one of HCl. Assume 10 molecules of each acid. Draw a picture of what
each solution looks like. What are the major species in each beaker?
|
|
33
|
- 2. Draw molecular-level pictures of the following:
|
|
34
|
- 3. Consider an aqueous solution of 2.0 ´ 10-3 M HCl. What are species in solution?
|
|
35
|
- 1. MH05/24. Which methods will distinguish between equimolar solutions
of a strong base and a strong acid?
- I. Add magnesium to each solution and look for the formation of gas
bubbles.
- II. Add aqueous sodium hydroxide to each solution and measure the
temperature change.
- III. Use each solution in a circuit with a battery and lamp and see
how bright the lamp glows.
- A. I and II only B. I and III only C. II and III only D. I, II and III
|
|
36
|
- 1. Complete each of the following reactions and write full ionic as well
as balanced net ionic equations. (If you don’t know the names of the
compounds name them too!)
- CaCO3 (s) + HCl (aq) ®
-
Full ionic Equation:
-
Net Ionic Equation:
-
NaSO3 (s) + CH3COOH
(aq) ®
-
Full ionic Equation:
-
Net Ionic Equation:
|
|
37
|
- Rb2O (s) + H2SO4 (aq) ®
- Full ionic Equation:
- Net Ionic Equation:
- Cu(OH)2 (s) + H2SO4 (aq) ®
- Full ionic Equation:
- Net Ionic Equation:
- NaHSO3 (s) + H2SO4
(aq) ®
- Full ionic Equation:
- Net Ionic Equation:
|
|
38
|
- MgS(s) + H2SO4 (aq) ®
- Full ionic Equation:
- Net Ionic Equation:
- NaOH (aq) + HCl (aq) ®
- Full ionic Equation:
- Net Ionic Equation:
- NaSO3 (aq) + H2SO4
(aq) ®
- Full ionic Equation:
- Net Ionic Equation:
- CaCO3 (aq) + CH3COOH (aq) ®
|
|
39
|
- 2. Write net ionic equations for the following reactions.
- a) Solutions of lithium carbonate and ethanoic acid are mixed.
- b) Solutions of sodium sulfide and sulfuric acid are mixed.
- c) A spatula of potassium hydrogensulfite is dropped in hydrochloric
acid in a beaker.
- d) A spatula of sodium oxide is added to ethanoic acid in a beaker.
- e) A small amount of magnesium sulfide is added to hydrochloric acid in
a beaker.
|
|
40
|
- f) A small coil of iron is dropped into sulfuric acid in a beaker.
- g) Copper(II) hydroxide is reacted is with hydrobromic acid.
- h) A solution of iron (II) sulfite is added to ethanoic acid.
- i) A solution of sodium hydrogen sulfite is added to sulfuric acid in a
beaker.
- k) Sulfur dioxide is bubbled through water.
|
|
41
|
- 3. MS03/7b. (i) Calcium carbonate is added to separate solutions of
hydrochloric acid and ethanoic acid of the same concentration. State one
similarity and one difference in the observations you could make. [2]
- (ii) Write an equation for the reaction between hydrochloric acid and
calcium carbonate. [2]
- (iii) Determine the volume of 1.50 mol dm–3 of hydrochloric
acid that would react with exactly 1.25 g of calcium carbonate. [3]
|
|
42
|
- (iv) Calculate the volume of carbon dioxide, measured at 273 K
and
1.01 × 105 Pa, which would be produced when 1.25 g
of calcium carbonate reacts completely with the hydrochloric acid.
[2]
- 4. MS03/7a. Define the terms strong acid and weak acid. Using
hydrochloric and ethanoic acid as examples, write equations to show the
dissociation of each acid in aqueous solution. [4]
|
Notes
