Module 3: Reactive Chemistry Flashcards
hydroxide
OH-
Nitrate
NO3 (-1)
Nitrite
NO2 (-)
Phosphate
PO4-3
Sulfate
SO4-2
Sulfite
SO3 (-2)
Carbonate
CO3 (-2)
ammonium
NH4 +
what is a physical change?
a type of change in which the form of matter is altered but one substance is not transformed into another.
What is a chemical change?
Chemical Changes occur when a new substance is formed and hence is called a chemical reaction
Physical change examples:
Melting Ice, boiling water, chopping wood
Chemical change examples:
Burning Wood, fireworks, cooking an egg`
Boiling of water versus electrolysis of water:
Boiling water= physical change as its particles remain the same. Electrolysis is a chemical change as it involves energy to remove separate hydrogen and oxygen molecules.
Indicators of a chemical change:
color change, formation of a precipitate, formation of a gas, odor change, temperature change
Model of chemical changes experiment:
-aim
Aim: To model what occurs at the atomic level during chemical reactions while ensuring that the law of conservation of mass applies
Model of chemical changes experiment:
-identify what occurred and why was it helpful
Identify- Modelling how bonds in chemical reactions are broken/formed
Describe: lollies= chemical and toothpicks= bonds
Explain: Chemicals + bonds/ reactions are too small to see, so models are used to teach a concept
what is a synthesis reaction?
A synthesis reaction involves the formation of a compound from its elements or from other, usually smaller, compounds.
Magenisum + Oxygen=
magnesium oxide
synthesis reaction
A non-metal oxide + water =
an acid
A metal oxide + water =
base
what is a decomposion reaction?
A decomposition reaction involves a single REACTANT breaking down to form a simple product. It usually involves energy from an external source (thermal or electrical)
Metal nitrate =
Metal nitrate + oxygen
decomposition
What is the Important example of a decomposition reaction?
electrolysis of water
metal carbonate=
metal oxide + Carbon dioxide
metal hydroxide =
metal oxide + water
What is ahydrocarbon?
Hydrocarbons (petrol, oil, coal, gas) contain hydrogen and carbon, because of this they make good fuels as energy is released when the bonds are broken following chemical reactions.
methane:
CH14
propane:
C3H8
ethane:
C2H6
Butane:
C4H10
Betane:
C5H12
What is complete combustion?
Hydrocarbons all burn in sufficient air or oxygen to produce carbon dioxide and water. Combustion is an exothermic chemical reaction. There is no net release of energy.
What is incomplete combustion?
Combustion requires oxygen, however in a low oxygen environment combustion can still occur but the products may be different. Carbon monoxide or soot (carbon) can result.
When does a precipitate form?
when the attraction between two oppositely charged ions is greater than the attraction between the individual ion and the water molecules. In this case, the oppositely charged ions will bond ionically to each other and precipitate out of the solution as an insoluble solid.
What is double displacement?
reactions occur when two elements in different compounds trade places:
What are the solubility rules?
-Soluble
- Group 1 + NH4+ compounds
- Nitrates
- chlorides ( except Ag+ and Pb2+)
- Sulfates ( except Ag+, Pb2+, Ba2+Sr2+, Ca2+)
What are the solubility rules?
-Insoluble
Carbonates (except group 1 and NH4+)
Hydroxides and oxides (except group 1, Nh4+ , Ba2+Sr2+, Ca2+)
Whats the difference between soluble and insoluble?
Soluble fiber dissolves in water, and Insoluble fiber doesn’t dissolve in water.
Whats an acid?
substance that in solution produces H+ ions
What are acids properties?
Taste sour, conduct electricity in solution , Ph < 7
What’s a base?
substance that in solution produces OH- ions
what are base properties?
feels slippery, tastes bitter, conducts electricity in solution, PH > 7
Hydrochloric acid:
HCL
Sulfuric Acid:
H2SO42+
Nitric acid
HNO₃
carbonic acid:
H2CO3
Acetic acid:
CH₃COOH
What is a neutralisation reaction?
When an acid and base react they form a neutral salt and water:
Acid + Base = Salt + Water
What are carbonates?
Carbonates are a group of ionic salts containing the polyatomic ion: CO32-.
Carbonates are basic salts as they can be used to neutralise acids.
What happens in an acid/ carbonate reaction?
When an acid and a metal carbonate reacts, a salt, Carbon dioxide and water are formed:
Acid + Metal Carbonate = Salt + Carbon Dioxide + Water
Reaction of Metals and Oxygen
All metals except silver, platinum and gold react with oxygen to form oxides.
Metal + Oxygen = Metal Oxide
Reaction of Metals and Water
Some metals react with water or steam while others do not.
Metal + Water = Metal Hydroxide + Hydrogen Gas
Reaction of Metals and Acid
Metals can react with acid to form a metal salt and hydrogen gas
Metal + Dilute Acid = Metal Salt + Hydrogen Gas
How do you know if a displacement reaction has occurred?
Using the standard activity series you can determine if a displacement reaction has occurred
What is an ionic equation?
shows how the ions present are reacting. In displacement reactions you can show how a metal is leaving its solid state to become an ion in solution. Or it can show how an ion in solution becomes a solid metal.
Describe the trends between metal activity and ionisation energy:
As you move across the periodic table, the number of valence electrons increase and therefore the ionisation energy increases. Similarly, as you move down the periodic table, the ionisation energy decreases because the attraction between the valence electrons and the nucleus decreases.
Describe the trends between metal activity and Atomic Radius:
Atomic radius increases down a group as an extra electron shell is added. Atomic radius decreases across a period due to the increasing size of the attractive charge from the nucleus which has the effect of drawing the outer shell electrons closer to the nucleus.
For the active metals in Groups I and II, atomic radius increases down the group, as does reactivity.
Describe the trends between metal activity and electronegativity:
Electronegativity increases from left to right across a period on the periodic table and decreases from top to bottom. This is opposite to their reactivity as they are less likely to lose an electron. Because of this group one metals are more reactive than group two as they are less likely to lose an electron.
What is a redox reaction?
A reaction in which one or more electrons are transferred from one atom to another
What is oxidation?
Loss of electrons
What is reduction?
Gain of electrons
OILRIG
Oxidation is loss reduction is gain
Apply the law of conservation to redox reactions:
There can be no overall loss or gain of electrons, therefore oxidation and reduction occur simultaneously.
What is an oxidising agent?
A substance that oxidizes another agent and therefore is reduced
What is a reducing agent?
A substance that reduces another agent and is therefore oxidised
Why were oxidation numbers developed?
Sometimes it is not easy to tell which species is oxidised or reduced. Due to the difficulties, chemists developed numbers that allow us to decide easily whether or not oxidation or reduction are involved
Oxidation rules:
The cation is always written first followed by the anion
The oxidation number for a free element is always=0
The oxidation number of a simple ion is equal to the charge of the ion
Group 1 and 2 metals have an oxidation number equal to the charge on their ions
Hydrogen has an oxidation number of +1 with non-metals
Oxygen normally has an oxidation number of -2
Chlorine,bromine and iodine are always -1, unless they are paired w oxygen
The sum of main group elements equals 0
The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion
What are half equations?
Are used to demonstrate the transfer of electrons.You must show whether the electrons are being lost or gained by writing them in the reactants (gained) or products (lost) side of the equation. Your electrons MUST be equal in both half equations.
What is a galvanic cell?
A galvanic cell is a cell capable of producing an electric current from a redox reaction that occurs within it
What do galvanic cells allow?
The conversion of chemical energy into electrical energy
What is a cathode?
a positive reduction electrode
What is an anode?
A negative oxidation electrode
What is the purpose of galvanic cells?
The purpose is to separate the oxidation and reduction half-cells in order to use the electricity which has been created in a spontaneous reaction.
How is a battery formed?
A battery is formed when multiple galvanic cells are placed in series to get a higher potential (voltage)
THE RED CAT ATE AN OX
reduction at cathode oxidation at anode
What is an electrode ? galvanic cells
Solid metal piece placed in solution
What is a solution? galvanic cells
What the electrodes are placed in. The solution will contain the ion of the specific electrode placed in it.
What is a salt bridge?
Contains ions to balance the charges formed in the 2 compartments. It is placed as a “bridge” between the 2 solutions. Cations move towards the cathode and anions move towards the anode.
What is a voltmetre?
Measures the voltage produced
What is a beaker galvanic cells
Holds electrolyte solution
What is a conducting wire galvanic cells?
Enables for the transfer of electrons and creates the circuit.
How does a galvanic cell work?
When the cathode and anode are connected by a conducting wire, electrons will naturally flow from the less electronegative metal to the more electronegative metal. In doing so, a current is produced, which can be measured using a microammeter
What is zinc in a galvanic cell?
Anode
oxidised
What is Copper in a a galvanic cell?
Cathode
reduced
What is the purpose of a salt bridge?
The salt bridge is a device that provides electrical contact between the two solutions. It allows ions to flow between the two beakers. As electrons are transferred from the oxidation half-cell to the reduction half-cell, a negative charge builds in the reduction half-cell and a positive charge in the oxidation half-cell. That charge build up would serve to oppose the current from anode to cathode, effectively stopping the electron flow.
Standard Electrode Potentials:
The table of standard reduction potentials provides a list of values that can be used to calculate the overall voltage of a galvanic cell and also to determine whether a reaction will occur spontaneously.
How do you know if a spontaneous reaction has occurred?
= a oxidising agent (reduced) must react with a reducing agent (oxidised) that is on the table of reduction potentials
If the value is positive, the reaction will occur spontaneously, if it is negative there will be no reaction.
Steps to calculate voltage of a redox reaction:
- Determine the starting species; iron is a metal, so Fe(s), copper is in solution so Cu2+.
- Find the first substance in the table: Fe(s) is the tenth equation, (although it is reversed);
Fe2+ + 2e- ⇌ Fe(s) - 0.44 V - Reverse the equation and sign if necessary; as we are starting with Fe(s) not Fe2+,
Fe(s) ⇌ Fe2+ + 2e- + 0.44 V - Find the second substance in the table: Cu2+ is the sixteenth equation;
Cu2+ + 2e- ⇌ Cu(s) + 0.34 V - Reverse the equation and sign if necessary (not necessary in this case).
- Add the two half-equations to find the net ionic equation and the overall voltage.
Fe(s) ⇌ Fe2+ + 2e- + 0.44 V
Cu2+ + 2e- ⇌ Cu(s) + 0.34 V
Cu2+ + Fe(s) ⇌ Cu(s) + Fe2+ + 0.78 V
What does rate of reaction mean?
the rate of change of concentration with time.
How do you calculate the average rate of reaction?
The average rate of reaction over a small time interval is the change in concentration divided by the time taken for the changes to occur.
What is a catalyst?
A substance that increases the rate of a reaction without undergoing permanent chemical change in the reaction
What is a homogenous reaction?
A Homogeneous reaction occurs when the reactants are present as a homogeneous mixture of gases or as a solution
What factors influence a homogenous reaction?
Concentration of the reactants
Nature and concentration of any catalyst
temperature
What is a heterogenous reaction?
reaction occurs at the interface of two phases such as between a gas and a solid or between a solution and a solid.
What factors influence a heterogenous reaction?
It is also affected by extra factors:
State of division of the solid involved
Rate of stirring/ or if it was stirred at all
WHat does the collision theory state?
The collision theory proposes that for a chemical reaction to occur, the reactant particles must:
Collide
Have more than a certain minimum amount of kinetic energy (in order to break the bonds)
Be correctly orientated ( to ensure that broken bonds don’t just reform but their is a new substance created as a result of the new bonds)
What is activation energy?
The minimum amount of energy reactants must have to undergo reaction. The more rapidly the rate increases with temperature, the larger the activation energy.
Why does kinetic energy make a reaction occur?
it breaks the bonds
WHy does orientation matter for reaction to occur?
to ensure that broken bonds don’t just reform but their is a new substance created as a result of the new bonds
What are enzymes?
Enzymes are biological catalysts that bring about important reactions in all living cells
WHat does a heterogenous catalyst do?
A heterogeneous catalyst works by providing a surface that can break or weaken chemical bonds in a reactant molecule absorbed on it
effect of temp on rate of reaction
Particles are always in motion and reactant particles may collide. If they don’t have enough energy, they will simply bounce off. Adding heat increases the kinetic energy allowing the particles to move quickly and have greater momentum when they collide
effect of surface area on rate of reaction
When we increase the surface area of a reactant, more individual particles, ion, atoms, molecules, etc. are exposed to any other reactant. This increases the number of collisions and hence the rate of reaction.
effect of concentration on rate of reaction
The greater the concentration, the larger number of reactant particles per unit volume, the greater the chances of collision and hence, the higher the reaction rate.
aboriginal example
The cycad palms in N and NE Australia. The fruit is cut and placed in mesh bags which are then soaked in water for several days. This allows time for toxic chemicals to leach out of the fruit. Insoluble starchy compounds remain after this process which are safe for consumptio
