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chapter 4 Flashcards

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1
Q

what is a reaction? what is used to represent them?

A

• A reaction is chemical changes in matter that results in
new substances
• A chemical equation is used to describe the reaction

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2
Q

what does the law of conservation of mass state?

A

From the Law of Conservation of Mass in a chemical

reaction, matter is neither created nor destroyed

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3
Q

can subscripts change? what must be included?

A

• Subscripts of atoms cannot change
• Must include subscripts to indicate the phase of the
chemical ie. (s), (l), (g), (aq)

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4
Q

what are coefficients used for?

A

Coefficients are used to balance the equation, but also
indicate the relative amounts required for a complete
reaction from reactants to product

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5
Q

what are the energy symbols?

A

! Δ = heat
! hν = light
!shock = mechanical
!elec = electrical

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6
Q

what do the coefficients specify?

A

The coefficients in a balanced chemical reaction specify
the relative amounts in moles of each of the substances
involved in the reaction

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7
Q

what are reaction stoichiometries?

A

• The numerical relationship between chemical amounts in

balanced reactions are the reaction stoichiometries

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8
Q

why do we need stoich?

A

• Cannot directly convert mass of reactants to mass of

products

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9
Q

what do stoichiometric ratios apply to?

A

• Stoichiometric ratios only apply to the molar ratios of
compounds
• Need to convert amounts into moles in order to predict
moles of product, which can then be converted to mass

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10
Q

why do we have limiting reagents?

A

• In the real world we don’t generally have exact
stoichiometric amounts of all reactants
• In addition, reactions rarely proceed with 100%
efficiency

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11
Q

what can we use to determine LR?

A

Based on the moles of starting material we can

determine the limiting reagent

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12
Q

How can we determine theoretical yield?

A

• Using stoichiometric ratios we can determine a

theoretical yield if the reaction goes to 100% completion

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13
Q

how can we determine percent yield?

A

Given the actual product amounts we can calculate the

percent yield

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14
Q

when do we have to determine the LR? what does the LR determine?

A

When we don’t have actual stoichiometric amounts of
reactants we need to determine the limiting reagent
• The limiting reagent determines the maximum amount of
product that can be formed
• To determine the limiting reagent compare the actual
ratio of reactants present to the stoichiometric ratio
found in the balanced equation

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15
Q

what is a homogeneous mixture? two parts of a solution?

A

• A homogenous mixture of two substances is known as a
solution
• A solution is made up of two parts: solvent and solute
• When a substance is mixed in water it is called an
aqueous solution (aq)v

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16
Q

what is the solvent?

A

• Solvent is the component
found in larger quantities
(water in aqueous solutions)

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17
Q

what is the solute?

A

Solute is the compound

found in smaller quantities

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18
Q

what happens when a solute dissolves in a solvent?

A

There are two competing interactions in a mixture:
solvent-solute and solute-solute
• When a solute dissolves in a solvent the solvent-solute
attractive forces are stronger than the solute-solute
interactions

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19
Q

how are electrolytes used?

A

In sports drinks they replace essential salts/ions we lose
through sweat
• For industrial applications they conduct electricity
• There must something in solution that allows the charge
to pass through from one electrode to the other

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20
Q

what do electrolyte solutions contain?

A

Electrolyte solutions contain dissociated ions
• Strong electrolytes contain fully dissociated ions (NaCl),
while weak electrolytes contain partially dissociated ions

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21
Q

what are solids that dissolve but do not dissociate called?

A

Solids that dissolve, but do not dissociate into ions are
called nonelectrolytes
sugar, molecular compounds

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22
Q

are ionic salts soluble?

A

Not all ionic solids (salts) are soluble in water
• There is no easy way to predict whether a solid will be
soluble or not

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23
Q

polyatomic ions?

A

When polyatomic ions dissolve they remain as intact
units
• Solubility exists on a continuum rather than an absolute
value

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24
Q

6 solubility rules

A 
1. All salts containing cations of group 1 metals (alkali
metals, Li+, Na+, K+, etc.) and ammonium ions (NH4
\+) are
soluble.
2. All nitrates (NO3
-
), ethanoates (acetates, CH3COO-),
chlorates (ClO3
-
), and perchlorates (ClO4
-
) are soluble.
3.Salts containing Ag+, Pb2+, and Hg2+ are insoluble.
4. Most chlorides (Cl-
), bromides (Br-
), and iodides (I-
) are
soluble.
5. Sulphates (SO4
2-) are soluble, except those containing
Ca2+, Sr2+, Ba2+.
6. Carbonates (CO3
2-), hydroxides (OH-
), oxides (O2-),
phosphates (PO4
3-), and sulphides (S2-) are generally
insoluble.
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25
Q

look at solubility tables

A

ok

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26
Q

what are compounds on the data table list?

A

Simply know
for now that if a compound
appears on this list, it is
insoluble.

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27
Q

what are the two main types of inorganic reactions that take place in aqueous media?

A

! Metathesis

! Oxidation-Reduction (redox)

28
Q

what are metathesis reactions?

A

Metathesis reactions are double replacement reactions
where the cations and anions of the reactants are
swapped
✓ AB + CD → AD + BC
✓ Driving force is the production of a precipitate or
formation of an unionized molecular compound (gas,
water, weak acid)

29
Q

when do precipitation reactions occur?

A

Precipitation reactions occur when we mix two solutions
together and a solid (precipitate) forms.
A precipitate will form only from insoluble compounds
Must determine which species are present in solution
and if any combination forms an insoluble compound

30
Q

how do we write molecular reactions? (precipitation)

A

shows the complete neutral formulas for each

compound as if they existed as molecules

31
Q

how do we write complete ionic reactions? (precipitation)

A

“lists all of the ions and species present in either

reactants or products

32
Q

how do we write net ionic reactions? (precipitation)

A

“shows only the reactant ions and products that take

part in the precipitation reaction

33
Q

what does a net ionic equation include?

A

• Ions that do not take part in the precipitation reaction are
called spectator ions
• The net ionic equation includes only the ions in solution
that react to form the insoluble precipitate

34
Q

Describe Arrhenius

A

Acids produce H+ in aqueous solutions
• Bases produce OH-
in aqueous solutions

35
Q

describe bronsted-lowry

A
  • Acids are proton donors

* Bases are proton acceptors

36
Q

describe lewis acid base

A

Acids are e-
pair acceptors
• Bases are e-
pair donors

37
Q

what is an acid base reaction also called?

A

An acid-base reaction is also called a neutralization
reaction
Protons associate with water molecules to form
hydronium ions H3O+
• Can be used interchangeably with H+

38
Q

what are strong acids and bases?

A

Acids and bases that 100% dissociate into ions are

called strong acids and strong bases

39
Q

what are weak acids and bases?

A

Acids and bases that do not completely dissociate into
the respective ions are called weak acids and weak
bases

40
Q

what are polyprotic acids?

A

Acids with more than one ionizable proton are polyprotic
acids
• Diprotic acids contain 2 ionizable protons
Can get analogous case with bases as well with X(OH)2
formula that can dissociate to give two OH-
(aq) ions

41
Q

strong acids and bases to remember

A 
HCl          LiOH
HBr         NaOH
HI            KOH
HClO4   RbOH
HNO3    CsOH
H2SO4   Ca(OH)2
                Sr(OH)2
               Ba(OH)2
42
Q

net ionic for neutralizations

A

H+(aq) + OH−(aq) → H2O

43
Q

what do an acid and a base produce?

A

acid + base → salt + water

44
Q

metal or hydrogen carbonates

A

Metal carbonates or hydrogen carbonates: React with
strong acids to produce carbonic acid, which degrades
into CO2(g) and H2O(l)

45
Q

metal and hydrogen sulphites

A

React with
strong acids to produce sulphurous acid, which
decomposes to give SO2(g) and H2O(l)

46
Q

metal sulphites

A

Metal sulphides: React with strong acids to produce

H2S(g) and a salt

47
Q

ammonium salts

A

: React with a strong base to form

ammonia and water

48
Q

what is the chemical event that occurs in redox?

A

The chemical event that occurs in a oxidation-reduction
(redox) reaction is the net movement of electrons from
one reactant to another

49
Q

what happens with redox of ionic compounds?

A

Ionic compounds transfer electrons

50
Q

what happens with molecular compounds?

A

Molecular compounds shift electrons

51
Q

what is oxidation? reduction?

A

Oxidation is the loss of electrons

!Reduction is the gain of electrons

52
Q

what are the oxidizing and reducing agents?

A

The oxidizing agent (O.A) causes the oxidation of the
other species
• The reducing agent (R.A) causes the reduction of the
other species. Therefore:
✓ The O.A. is reduced
✓ The R.A. is oxidized

53
Q

what can we use to remember redox reactions?

A

OIL RIG

LEO the lion goes GER

54
Q

how do we know if redox has occurred?

A

OXIDATION NUMBER
• The oxidation number of an atom in a compound is the
charge it would have if shared electrons were assigned
to atoms with the greatest attraction for electrons

55
Q

what is the oxidation number in binary ionic compounds?

A

In binary ionic compounds the oxidation number is the

same as the ionic charge

56
Q

rules for oxidation numbers of elements and mono atomics

A
  1. Atoms in elemental form have an oxidation number of
    zero (0)
    • Cl2, O2
  2. The oxidation number of a monoatomic ion is equal to
    the ion’s charge
    • Fe2+, Ca2+
57
Q

rules for oxidation numbers of neutral compounds, polyatomics, and metals in compounds

A

The sum of the oxidation numbers of all atoms in:
• a neutral molecule is always 0
• H2O, HCl
• a polyatomic ion is always equal to the charge of
the ion
• SO3
2-, NO3
-
4. In their compounds, metals always have positive
oxidation states:
• Group 1 metals always have a +1 oxidation number
• Group 2 metals always have a +2 oxidation number

58
Q

oxidation numbers for hydrogen and nonmetals in compounds

A
  1. The oxidation state of hydrogen in a compound is
    usually +1
  2. In their compounds, the nonmetals typically have
    negative oxidation states:
    • Fluorine always has an oxidation number of -1
    • Other Group 17 elements usually have an oxidation
    number of -1
    • Oxygen usually has an oxidation number of -2
    • Other Group 16 elements usually have an oxidation
    number of -2
    • Group 15 elements usually have an oxidation number
    of -3
59
Q

what happens with elements that aren’t covered by these rules?

A

Some elements are not covered by these rules
• Need to determine the oxidation numbers of elements
covered by the list and then use Rule 3 to determine the
oxidation number of the remaining elements
• Rules higher up on the list take precedence over rules
lower down the list

60
Q

can compounds have multiple oxidation numbers?

A 
yes, The oxidation state of
a particular element is
dependent on the
other atoms bonded
to it
61
Q

how can we tell if an atom has oxidized? reduced?

A

If an atom has a higher (more positive) oxidation number
in the products than it had in the reactants, then the
reactant that contains that atom was oxidized
• If an atom has a lower (more negative) oxidation number
in the products than it had in the reactants then the
reactant that contains that atom was reduced

62
Q

summary

A 
Oxidation Reduction
Loses e- Gains eReducing
agent
Oxidizing
agent
Increased
O.N.
Decreased
O.N.
63
Q

what does molarity describe? formula?

A

We use the term molarity to describe the amount of
solute present in 1 litre of solution
• Molarity: M (mol/L)
• M = n/V, where n = the number of moles of solute

64
Q

how is molarity used in calculations?

A

Molarity of a solution shows the relationship between
the amount of solute (in moles) and the solvent (in litres)
• If a salt solution is 2M, then 1 litre of water contains 2
moles of salt
!4L = 8 moles

ex How many moles of KCl are there in 0.65 L of a 1.5M
KCl solution?
L solution mol KCl 1.5 mol KCl
1 L
0.65 L ×
1.5 mol KCl
1 L
= 0.98 mol KCl
65
Q

how do we dilute a solution? formulas?

A

In the laboratory, solutions are often stored as stock
solutions
• To make solutions of lower concentration we add more
solvent
! The amount of solute doesn’t change, only the
volume
!moles of solute in solution 1 = moles of solute in
solution 2

M1V1 = M2V2 
C1V1 = C2V2

chem 101 (13 decks)

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