Chemistry Flashcards
Relative mass of an electron
1/1870
Relative mass of a proton
1
Relative mass of a neutron
1
Relative charge of a neutron
0
Relative charge of a proton
+1
Relative charge of an electron
-1
Atomic number
Same as the number of electrons
Number of electrons in positively charges ions =
Atomic number - charge on ion
Number of electrons for negatively charged ions =
Atomic number + charge on ion
Does the number of protons in an atom change during a chemical reaction?
No, the nucleus isn’t involved in chemical reactions
Mass spectra show the relative abundance against the mass/ charge ratio, what does this show?
The abundance of isotopes
Reactivity down group 1
Increases
Ammonia
NH3
Carbon Dioxide
CO2
Carbon monoxide
CO
Methane
CH4
Nitrogen dioxide
NO2
Nitrogen monoxide
NO
Sulfur dioxide
SO2
Sulfur trioxide
SO3
Water
H2O
Ammonium
NH4+
Carbonate
CO32−
Hydroxide
OH-
Nitrate
NO3−
Sulfate
SO42−
Ethanoic acid
CH3COOH
Buckminsterfullerene
C60
Acid + Alkali
Salt + water
Acid + Carbonate
Salt + water + carbon dioxide
Acid + Ammonia
Ammonium salt
Acid + metal
Salt + hydrogen
Dynamic equilibrium
No chemicals can get in or out, reversible reactions can reach a state of dynamic equilibrium. At this point, both the forwards and reverse reaction are taking place simultaneously and at the same rate
More reactants
Moves eqm to the right
More products
Equilibrium moves to the left
Increase temperature on an exothermic reaction
Moves reaction to the endothermic direction (to the left) to lower the temperature
Increasing temperature on an endothermic reaction
Moves reaction to exothermic side (to the right) to increase the temperature
Increase pressure
Moves to sides with fewer particles
Isotope definition
Variations of elements that differ only in neutron number - abundance from mass spectrometer
RAM definition
Average atomic mass of a chemical element found relative to 1/12th the mass of a sample of C12
How are elements grouped?
According to electron number - which results in similar chemical properties
How to construct an ionic equation
Split up (aq) ions and remove the spectator ions (solids and liquids can be present but only if not on both sides of the equation)
Reversible reaction
Reaction that doesn’t go to completion as not all the reactants turn into products (closed system) - Eqm is reached when the forward rate = the backward rate
Avogadro’s number
6.02 x10^23 = number of particles in 1 mole of a substance
% composition by mass =
(mass/ total mass) x 100
How to calculate masses of products which reagent do you use?
Limiting
Ideal gas occupies…
24dm^3 at a given temperature and pressure
Volume (dm^3) when given moles =
n (moles) x Vm (24dm^3)
Number of moles given conc. and volume =
Concentration (mol dm^-3) x Volume (dm^3)
How to perform a titration calcuation
Use conc. and reacting ratios from a balanced equation
Oxidation is…
Gain of oxygen, loss of hydrogen or loss of electrons
Reduction is…
Loss of oxygen, gain of hydrogen or gain of electrons
Oxidation state of O
-2
Oxidation state of H
+1
Oxidation state of G1 Metals
+1
Oxidation state of G2 Metals
+2
Oxidation state of Cl
-1
Disproportionation
Reduction and oxidation occur to the same element in the same equation
Oxidising agent
Thing being reduced
Reducing agent
Thing being oxidised
Element definition
Primary constituent of matter, distinguished by it’s atomic number
Compound definition
Composed of 2 or more elements - inseparable
Mixture definition
2 or more elements - separable
How are ions formed?
By the transfer of electrons from metals to non-metals (ions of opposite charge attract to form ionic compounds)
Group 1 and 2 form what ions?
+1 and +2 respectively
Group 6 and 7 form what ions?
-2 and -1 respectively
Common features of ionic compounds
High melting/ boiling points (strong oppositely charged electrostatic forces of attraction), electrical conductor when melted or aqueous (charged particles can move) and giant ionic lattice structure
Covalent bond
Atoms share 1 or more pairs of electrons
Small covalent examples
H2O, NH3 and CH4
Giant covalent examples
Diamond, graphite and silicon dioxide
Simple covalent properties
Low mpts and bpts (weak intermolecular forces of attraction) and don’t conduct (no free electrons to carry charge)
Giant covalent properties
Very high mpts and bpts (strong covalent bonds must be broken) and variable electrical conductivity (depends on availability of free electrons)
Structure in metals
Giant structure of positively charged cations surrounded by free moving delocalised electrons
Properties of metals
High mpt and bpts (lattice structure with electrostatic forces) and conduct electricity (free moving electrons to carry charge)
What cause physical properties of substances
Structure AND bonding
Properties and common reactions of Group 1
Silvery, soft, highly reactive, low melting points that decrease down the group, react with water to form metal hydroxides and H2
Properties of Group 7 elements
Get darker down the group, low melting and boiling points that increase down the group (larger atoms)
Properties of Group 8 elements
Low boiling points that increase down the group, inert because of full outer shell
How do displacement reactions occur?
More reactive displace elements with lower reactivities (result of the ability to attract valence electrons)
What does a pure substance give on a chromatogram?
1 single spot
Acid definition
Substance that can form H+ ions in solution or is an H+ donor
Acid + Metal ->
Salt + Hydrogen
Acid + Carbonate ->
Salt + water + CO2
Acid + metal hydroxide ->
Salt + water
Acid + Base ->
Salt + Water
Acid + metal oxide ->
Salt + Water
Strong
Completely dissociate into ions in solution
Weak
Partially dissociate into ions in solution
Dilute
Low conc. of ions
Concentrated
High conc. of H+ ions
pH is a measure of…
H+ ion concentration on a logarithmic scale
What is a di/tri/polyprotic acid?
Can donate more than 1H+ ion
Base definition
Forms OH- ions in solution and/ or accept H+ ions
Acid + Base ->
Salt + Water (neutralisation) and normally exothermic
Increase concentration on rate of reaction
Faster - more reactant particles
Increase temp on reaction rate
Faster - more energy and collisions
Increase particle size on rate
Slows - surface area
Add a catalyst to the rate
Faster - more collisions
Increase pressure on rate
Faster - more collisions
Collision theory
Reaction progression dependent on the correct collision and alignment of the particles
Exothermic diagram
Products lower than reactants
Endothermic diagram
Products higher than reactants
Catalysts key features
Not used up, chemically unchanged by the end of a reaction, provide and alternate reaction mechanism with a lower Ea - Don’t affect position of EQM
Exothermic reaction H =
-ve
Endothermic reaction H =
+ve
Bond breaking
Endothermic
Bond forming
Exothermic
H from bond energies =
Reactants - Products
Electrode
Solid electrical conductor that carries current into a non-metallic compound
Cathode
Negative electrode
Anode
Positive electrode
Electrolyte
Substance that produces an electrically conducting solution when dissolved in a polar solvent (eg. H2O)
Why is AC not used in electrolysis
Would constantly switch the anode and the cathode - leading to an uneven deposition of ions
Anode formation
Anions (-) loose electrons to form atoms/ molecules (oxidation)
Cathode formation
Cations (+) receive electrons to form atoms/ molecules (reduction)
Electrons on half equations for OX/ RED
Left side for RED
Right side for OX
What is formed at electrodes?
Aq solutions can attract more than one ion at an electrode (one rules) and molten binary compounds only contain 2 elements
Longer carbon chain properties
More viscous, higher bpt/ mpts and smokier flames
Homologous series definition
Species with the same functional group that exhibits similar chemical properties
Br2 test
Decolourises in an alkene
Alcohol + Na ->
Sodium ethoxide and H2
Carboxylic ACID
Weak acids - don’t fully dissociate
COOH + OH
Produce an ester
Reactivity series mnemonic
Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold
Electrolysis separates…
Most reactive metals from their compounds
Alloy
Metal combination
Metal ore
Always involve reduction (they are metal OXIDES)
Transition metal properties
Stable ions in variable oxidation states, coloured compounds and often used as ion/ atom catalysts
State changes overcome
Forces of attraction
H2 gas test
Squeaky pop with a lit splint
O2 test
Relights a glowing splint
CO2 test
Turns limewater cloudy
Chlorine test
Damp blue litmus turns red then bleaches
Carbonate ion test
Bubbles when in presence of dilute acid
X- ion test
Aq solution of silver nitrate and dilute nitric acid gives white for Cl, cream for Br and yellow for I
Sulphate ion test
Barium chloride in presence of dilute HCl - white sulfate of barium sulfate is +ve result
Metal cation test in NaOH for Al3+, Ca2+ and Mg2+
White ppt
Metal cation test in NaOH for Cu2+
Blue ppt
Metal cation test in NaOH for Fe2+
Green ppt
Metal cation test in NaOH for Fe3+
Brown ppt
Flame test for Li
Crimson red
Flame test for Na
Yellow/ orange
Flame test for K
Lilac
Flame test for Ca
Red/orange
Flame test for Cu
Green
Test for presence of H2O
Anhydrous Copper (II) Sulfate gives a white to blue colour change
Dangers of CO2
Global warming (traps IR - UV) + acid rain
Dangers of CO
Toxic to haemoglobin
Dangers of SO2
Respiratory problems + acid rain
Dangers of NOx
Ecosystem damage + breathing problems
Electrolysis definition
Ionic substances are broken down into simpler substances as an electric current is passed through them
Covalent cannot act as electrolytes because…
They don’t contain ions, but neutral atoms
Ions in electrolysis must be …
Free to move - so when an ionic substance if dissolved in water of when it is melted
Positively charged ions move to the
Negative electrode (cathode) during electrolysis. They receive electrons and are reduced
Negatively charged ions move to the…
Positive electrode (anode) during electrolysis. They lose electrons and are oxidised. The substance that is broken down is called the electrolyte
Where is the metal and non-metal found in electrolysis
the metal is formed at the negative electrode because that is where the positive metal ions are attracted
the non-metal element is formed at the positive electrode where the negative non-metal ions are attracted
What is formed at the negative electrode?
The metal if it is less reactive than H2 (Copper, Silver or Gold) - otherwise H2 is produced
At the positive electrode
If the negative ion is simple - then that element will be produced (eg: Bl- or Cl-) otherwise it is O2
Charge transferred during electrolysis can be calculated from the mean current used and time taken:
Charge (Q (C)) = Current x Time
One faraday is 1 mole of electrons and equal to
96500 Coulombs
When should you use an inert electrode?
An inert electrode is needed to conduct the electrons but it is not part of the redox reaction. You only need an inert electrode (like Pt) if your reactants cant function as an electrode (like I2 and Ce ions). If you have a metal like Zn, Cu or Ag involved you can just use the metal
Copper, zinc, lead, and silver can all be used as participatory electrodes
How does electroplating work?
The negative electrode should be the object to be electroplated.
The positive electrode should be the metal that you want to coat the object with.
The electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate.
