Chem Final Exam: big pack Flashcards
What are the 3 states of matter? (most energy, to least energy)
-Gas
-Liquid
-Solid
Solid:
-regular arrangement
-fixed positions
-vibrating on the spot
-touching/very close
Liquid:
-random arrangement
-moving around
-close together/touching
Gas:
-particles have the most energy (move the fastest)
-particles are the most spread apart
-random arrangment
Interconversions between three states of matter:
Gas -> Liquid: condensation
Liquid -> Solid: freezing (all 3 deposition)
Solid -> Liquid: melting
Liquid -> Gas: evaporation (all 3 sublimation)
What is deposition?
particles lose kinetic energy, move less and become more regualrly arranged and close together
What is sublimation?
particles gain more energy, move around more and become more randomly arranged and further apart
Dilution of coloured solutions and diffusion of gases:
-movement of particles from an area of high concentration to an area of low
-doesn’t occur in solids, since the particles are fixed together
-coloured solutions are diluted by adding water, because the particles of the colour diffuse to the air of low concentration, mixing it with the water molecules, causing dilution to occur
Solvent:
liquid in which the solute is being dissolved
Solute:
substance that dissolves in a liquid to form a solution
Solution:
mixture formed when a solute has dissolved in a solvent
Saturated solution:
solution in which no more solvent can be dissolved
Element:
substance made from only one type of atom
Compound:
2 or more atoms chemically bonded together
Mixture:
-2 or more particles mix together
What are pure substances?
-> made from only 1 type of atom
-they melt and boil at specific temperatures
Simple distillation: (l->s)
-used to separate out liquids from solutions
-solution is heated, the part of the solutions that has lowest boiling point evaporates
-vapour then cools, condenses and is collected
Fractional distillation: (m->l)
-used to seperate mixtures of liquids
-liquid with the l.b.p evaporated first, when temp of thermomter matches b.p of liquid, it will reach the top of the column
-liquid with h.b.p might also evaporate, but column is cooler towards the top
Filtration: (i,s -> l)
-used to seperate an insoluble solid from a liquid
-liquid part runs through the paper, leaving behind the solid residue
Crystillisation: (s,s -> s)
-separates a soluble solid from a solution
-some water evaporates and the solution gets more concentrated
-the salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
Paper Chromatography: (m)
-used to separate mixtures and give information to help identify them
-the more soluble a substance is, the further up the paper it travels
Equation for the Rf value: (chromatography)
Rf = distance travelled by solute/distance travelled by solvent
Atom:
smallest piece of an element that can exist
-all substances are made of atoms
Molecule:
formed when atoms join together by chemical bonds
Proton: subatomic particle (r.m, r.c, p)
relative mass: 1
relative charge: +1
position: in the nucleus
Neutron: subatomic particle (r.m, r.c, p)
relative mass: 1
relative charge: 0
position: in the nucleus
Electron: subatomic particle (r.m, r.c, p)
relative mass: 0.0005
relative charge: -1
position: in shells around the nucleus
Atomic (proton) number:
-tells you how many protons there are
number of electrons = number of protons
Mass (nucleon) number:
-number of protons + number of neutrons
-to get n. of neutrons, just subtract the atomic number from the mass number
Isotopes:
different atoms of the same element containing the same number of protons but different numbers of neutrons
eg:
Carbon-12: 6 protons, electrons, neutrons
Carbon-13: 6 protons, electrons and 7 neutrons
Relative atomic mass (of an element):
-average mass (relative abundance) of all isotopes in an element
-A.R = (% of isotope A x mass of isotope A) + (% of isotopw B x mass of isotope B) /100
Metals
elements that react to form positive ions
Non-metals:
elements that react to form negative ions
Group number:
gives number of electrons in outer shell e.g. group 3 has 3 electrons in their outer shell
Period number:
gives number of electron shells e.g. period 1 has 1 shell of electrons
Noble gases: Group 0
-They have 8 electrons in their outer shell (except helium, that has 2)
-they are unreactive and do not easily form molecules, because they have a stabble arrangement of electrons
How to balance an equation?
-(g) means gas, (s) means solid, (l) means liquid, (aq) means aqueous
-eg: HCl + NaOH -> NaCl + H2O
-to balance an equation: you need to make sure that there are the same number of each element on each side e.g. 3H2O
Relative Formula Mass:
-you have to add up the r.a.m of the atoms
eg: Ammonium Sulfate: ((NH4)2SO4) = (2 x 14) + (8 x 1) + 32 + (4 x 16) = 132
What are moles? (mol)
-chemical amounts are measured in moles (its the amount of a substance)
6.02 x 10^23 “Avogrado’s number”
Moles = Mass/Ar or Mr
Percentage yield:
-amount of product obtained is known as yield
Percentage yield = amount of product produced/theoretical mass of product x 100
What is the Empirical formula?
-if you have a common multiple e.g. Fe2O4, the empirical formula is the simplest whole number ratio, which would be FeO2
-if there is no common multiple , you already have the empirical formula
What is the Molecular formula?
-multiply the number of each element present in the empirical formula by this number to find the molecular formula
-if answer was 2 and the empirical formula was Fe2O3 then the m.f would be e.f x 2 = Fe4O6
Ions:
atoms that have lost or gained electrons
Cation:
+ ions, formed by gaining electrons, metal
-single atoms which have lost either 1,2 or 3 electrons to achieve a FULL outer shell, molecules with a net POSITIVE CHARGE
Anion:
-ions, formed by losing electrons, non-metal
-single atoms which have gained either 1,2 or 3 electrons to achieve a FULL outer shell, molecules with a net NEGATIVE CHARGE
What do ions in Group 1 form?
1+ ions
What do ions in Group 2 form?
2+ ions
What do ions in Group 3 form?
3+ ions
What do ions in Group 5 form?
3- ions
What do ions in Group 6 form?
2- ions
What do ions in Group 7 form?
1- ions
What is the Sulphate ion?
SO4 2- (2-goes on top)
What is the Carbonate ion?
CO3 2- (2-goes on top)
What is the Nitrogen ion?
NO3 - (- goes on top)
What is the Hydroxide ion?
OH - (- goes on top)
What is the Ammonium ion?
NH4 + (+ goes on top)
What is the Silver ion?
Ag + (+ goes on top)
What is the Zinc ion?
Zn 2+ (2+ goes on top)
What is the Copper ion?
Cu 2+ (2+ goes on top)
What is the Lead (II) ion?
Pb 2+ (2+ goes on top)
What is the Hydrogen ion?
H + (+ goes on top)
What is the Iron (II) ion?
Fe 2+ (2+ goes on top)
What is the Iron (III) ion?
Fe 3+ (3+ goes on top)
Ionic Compounds:
-formed when a metal and non-metal react
-formed by the transfer of eletcrons from the outer shell of the metal to the outer shell of the nonmetal
-the metal therefore forms a positive ion and the non-metal forms negative ion
How are the electrostatic attractions of ionic bonds?
-a giant structure of ions = ionic compound
-held together by strong electrostatic forces of attraction between oppositely charged ions
-the forces act in all directions in the lattice
Why do compounds with giant lattice structures have high melting/bioling points?
-strong electrostatic forces of attraction between oppositely charged ions
-requires a lot of energy to overcome these forces of attraction
Do ionic compounds conduct electricity?
-as a solid, the ions are in fixed positions so can’t conduct electricity
-when molten or in aqueos solution the ions are free to move carrying charge and coducting electricity
What are Covalent Bonds?
-occurs in most non-metallic elements and in compounds of non-metals
-when atoms share pairs of electrons, they form covalent bonds, strong bonds between atoms
How are the electrostatic attractions of covalent bonds?
-strong bonds between atoms that are covalently bonded are the result of electrostatic attraction between the positive nuclei of atoms and the pairs of negative electrons that are shared between them
What are intermolecular forces in covalent bonds? (Substances that consist…)
-substances that consist of small molecules are ususally gases or liquids that have low boiling and melting points
-substances that consist of small molecules have weak intermolecular forces between the molecules: These are broken in boiling or melting, not covalent bonds
-Substances that consist of small molecules don’t conduct electricity, because small molecules do not have an overall electric charge
Why do boiling/melting points of substances with simple molecular structures increase?
-the intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points
Why are substance with giant covalent substances solids with high melting/boiling points?
-substances that consist of giant covalent structures are solids with very high melting points
-all of the atoms in these structures are linked to other atoms by strong covalent bonds
-these bonds must be overcome to melt or boil these substances
What is the structure of a diamond?
-Each carbon is joined to 4 other carbons covalently
-It’s very hard, has a high melting point and does not conduct electricity
What is the structure of graphite?
-Each carbon is covalently bonded to 3 other carbons, forming layers of hexagonal rings,
-Between the layers there are weak forces of attraction
-The 4th unbound electron is delocalised and can move along layers
-Good conductor of electricity
-Layers can slide over eachother: good lubricant (soft + slippery)
What is the structure of Fullerences?
-C60 carbon atoms form a big ball of atoms where 3 c.b are established with other carbons, and the 4 unbound electron is delocalise
-Made up of large covalent molecules held together by intermolecular forces
-It is soft, can slide over each + poor conductors
What covalent compounds conduct electricity?
-graphite
-graphene
What do the Alkali metals have in common?
-They all have properties due to the single electron in their outer shell
-React vigorously with water to create an alkaline solution and hydrogen
What are the differences between the rxns of the Alkali metals that show a trend in reactivity?
-They all react with oxygen to create an oxide
-More bubbles with reaction with water = more vigorous rxn = more reactive alkali metal
-Reactivity increases down the group -> therefore reactivity increases from Li to K
What happens when Li reacts with H20?
frizzes steadily
What happens when Na reacts with H20?
melts into a ball then frizzes quickly
What happens when K reacts with H20?
gives off sparks and hydrogen burns with lilac flame
What is the trend in reactivity for Alkali metals?
increase in reactivity down the group
What are the colours of these elements at room temp. + trends in physical properties?
Chlorine is a green gas
-Bromine is a red-brown liquid
-Iodine is a purple solid
-There is a trend in state from gas to liquid to solid down the group
What are the properties of other halogens?
-There is a trend in state from gas to liquid to solid down the group
-this is because the melting and boiling points increase as you go down the group
-from this, you can predict that any halogens above chlorine will be gases (their boiling points will be even lower), and any below iodine will be solids (their melting points will be even greater)
How do displacement rxn involving hallogens and hallides affect the trend?
-a more reactive halogen can displace less in an aqueous solution of its salt
-e.g. Chlorine will displace bromine if you bubble the gas through a solution of pottasium bromide
Chlorine (green) + Potassium Bromide -> Potassium Chloride + Bromine (red)
-this happens because as you go down the group, the reactivity of halogens decreases
What is the trend in reactivity for Halogens?
decrease in reactivity down the group
What are the approximate percentage of the most abundant gases in the air? (4)
78% nitrogen, 21% oxygen, 0.9% argon and 0.037% carbon dioxide
Eg rxn: copper to determine % volume of oxygen
copper + oxygen -> copper (ii) oxide // 2Cu (s) + O2 (g) -> CuO (s)
What is combustion?
-combustion is an example of oxidation
-in an oxidation rxn, a substance gains oxygen
-metals and non-metals can take part in these rxns
eg: hydrogen + oxygen -> water // 2H2 + O2 -> 2H2O
How is carbon dioxide formed from thermal decomposition?
-Metal carbonate -(heat) -> metal oxide + carbon dioxide
-E.g. copper (II) carbonate-(heat) -> copper (II) oxide + carbon dioxide // CuCO3 -> CuO + CO2
How is climate change affected?
-greenhouse effect mantains temperatures on Earth high enough to support life
-Greenhouse gases include: water vapour, CO2 and CH4
-Global warming is an ‘enhanced greenhouse effect’
-An increase in average global temperature is a major cause of climate change
Explanation of greenhouse gas effect:
-electromagnetic radiation at most wavelengths from the sun passes through the Earth’s atmosphere
-The Earth absorbs some radiation and thus warms up, but some heat is radiated from the Earth as infrared radiation
-Some of the IR radiation is absorbed by greenhouse gases in the atmosphere
-atmosphere warm up leading to the greenhouse effect and global warming
