chemistry Flashcards
what explains the trend seen in thermal stability of group 2 carbonates
Carbonate ions can be made unstable due to a cation (group 2 metal ion), causing the carbonate ion to be polarised (as it has electrons drawn towards itself). Polarisation distorts the carbonate ion and the more it is distorted, the less stable it will be. Larger cations (moving down group 2) cause less distortion because their electrons are spread out over a larger area. Therefore, the carbonate ion will be distorted less so it will be more stable.
strucutre of the atom
central nucleus (containing protons and neutrons) surrounded by electrons moving in shells/energy levels.
relative masses and charges of protons, neutrons and electrons, and recognise that most of the mass of an atom is in the nucleus.
mass of proton: 1
mass of neutron: 1
mass of electron: n/a
charge of proton: +1
charge of neutron: 0
charge of electron: -1
isotope
atoms of an element with the same number of protons but different numbers of neutrons (so having different mass numbers).
using
mass spectrometers
relative atomic mass symbol
Ar
elements are arranged in order of
increasing atomic number
alkali metals are
group 1
alkaline earth metals are
group 2
common non metals
group 16
halogens are
group 17
noble gases are
group 18
elements in the same group…
have similar chemical properties
increasing reactiivty down a metal group and decreasing reactivity down a non metal group
what factors affect pos of e
concentration of reactants/products, temperature, overall pressure
avogadros number gives
the number of particles of one mole of a substance
one mole of a substance is the what
Ar or Mr in grams
grams to moles
divide by Ar or Mr
moles to grams
multiply by Ar or Mr
1 tonne is
1000 kg
moles to number of atoms or molecules
multiply by avogadros (6.022 x 10^23)
amount of substance corresponds to
the number of moels of a substancce
empirical formula is
the simplest integer ratio of atoms in a compound. Find the empirical formula of a compound from a variety of data, such as the percentage composition by mass of the elements present or reacting masses
one mole of gas occupies what at a given rtp
24 dm cubed
percetnage yield
actual yield/theoretical yield x 100
oxidation is
gain of oxygen
loss of electrons
reduction is
removal of oxygen
gain of electrons
oxidising agent
gets reducted
does oxidising
reducing agent
gets oxidised
does reducing
how are ions formed
by transfer of electrons from atoms of metals to atoms of non-metals, and that these ions (of opposite charge) attract to form ionic compounds
when are roman numerals used
when an element can exist in more than one oxidation state
a covalent bond is
when atoms share one or more pairs of electrons, generally between non metals
metallic bonding is
solid metals exist as a giant structure of positively charged ions surrounded by delocalised (free) electrons.
small covalent molecules
water
ammonia
methane
giant covalent structures
diamond
graphite
silicon dioxide
what forces are ovecome in melting or boiling
intermolecular
chemical processes are require dto
displace consitiuent elements from their compounds
physical provesses are required to
separate mixtures, including miscible/immisicible liquids and dissolved/insoluble solids
an acid is a substance that can form
H+ ions or is a H+ donor
metal +
salt +
physical properties of group 1
are soft (they can be cut with a knife)
have relatively low melting points
have low densities
chemical properties of group 1
reaction with moist air
reaction with water
physical properties of group 17
simple molecules
2 halogen atoms joined by a single covalent bond
mp and bp increase going down group 7
the molecules become larger
the intermolecular forces become stronger
more energy is needed to overcome these forces
chemical properties of group 17
react with metals to produce salts
reactivity decreases going down the group
physical properties of group 18
inert
low densities
what is a displacement reaction
Displacement reactions involve a metal and the compound of a different metal. A more reactive metal will displace or push out a less reactive metal from its compound in a displacement reaction. The less reactive metal is left uncombined after the reaction. It is no longer chemically bonded to any other elements. It is now a pure element.
one mole of some acidic substances is able to form/donate
more than on emole of H+ ions
(mono-, di-, tri-, and polyprotic.)
a base is a substance
that can form OH- ins or that is an H+ acceptor
when do you use simple distillation
Distillation separates a liquid from a solution. For example, water can be separated from salty water by simple distillation. This method works because the water evaporates from the solution, but is then cooled and condensed in a condenser and collected in a separate container. The salt does not evaporate and so it stays behind.
when do you use fractonal distillation
Fractional distillation separates miscible liquids that have different boiling points. It is useful for separating ethanol from a mixture of ethanol and water, and for separating crude oil into different products such as petrol, diesel and kerosene.
when do you use paper chromatography
Chromatography can be used to separate mixtures of coloured compounds. Mixtures that are suitable for separation by chromatography include inks, dyes and colouring agents in food.
Simple chromatography is carried out on paper. A spot of the mixture is placed on a pencil line near the bottom of a piece of chromatography paper – the line must be in pencil because pencil is insoluble in water and so will not move as the chromatography progresses. The paper is then placed upright in a suitable solvent, such as water.
As the solvent soaks up the paper, it carries the mixtures with it. Different components of the mixture will move at different rates. This separates the mixture out.
when do you use a seperating funnel
separate immiscible liquids
when do you use centrifugation
to separate molecules of varying density A substance containing two different molecules, let’s say, is placed in a solution and put inside what’s called a centrifuge.
when do you use filtration
This technique is used to separate an insoluble solid from a liquid. It can be used to obtain a product that is free from unreacted chemicals, by-products or solvent.
when do you use evaporation
One way to separate a soluble solid from its solution is to make crystals. This involves evaporating the solution to a much smaller volume and then leaving it to cool. As the solution cools, crystals form, and these can be obtained by filtration.
bond breaking is
endothermic
bond making is
exothermic
cathode
negative electrode
anode
positive electrode
describe electroloysis
the cations (positively charged ions) receive electrons (reduction) to change into atoms or molecules, and at the anode, the anions (negatively charged ions) lose electrons to form atoms or molecules (oxidation).
crude oil is the main source of
hydrocarbons
how is crude oil sepearted into fractions
fractional distillation
alkanes general formula
CnH2n+2
which are saturated
alkanes
alkenes general formula
CnH2n
addition reactions occur with which substances
hydrogen, halogen, hydrogen halides and steam
addition polymerisation
alkenes or other molecules with a C=C bond may react with each other to form long-chain saturated molecules called polymers by addition reactions called polymerisation, and that the unsaturated molecules are called monomers.
alcohol general formula
CnH2n+1OH
carboxylic acids general formula
CnH2n+1COOH
reactivity of a metal is linked to
its tendency to form positive ions and the ease of extraction of the metal.
most metal ores are
the oxides of the metal
extraction of metal requires
reduction processes
common properties of transition metals include:
a. they are able to form stable ions in different oxidation states
b. they often form coloured compounds
c. they are often used as catalysts (as ions or atoms).
the energy required for these processes: freezing, melting, boiling/evaporating, and condensing,
is related to the bonding and structure of the substance, including a consideration of intermolecular forces.
hydrogen –
explodes with a ‘squeaky pop’ when a burning splint is held at the open end of a test tube
oxygen –
relights a glowing splint
carbon dioxide –
limewater turns cloudy when shaken with the gas
electrode
a conductor through which electricity enters or leaves an object, substance, or region.
carbonates –
using a dilute acid
halides –
using an aqueous solution of silver nitrate in the presence of dilute nitric acid (chlorides form a white precipitate; bromides form a cream precipitate; iodides form a yellow precipitate)
eletrolyte
a liquid or gel which contains ions and can be decomposed by electrolysis, e.g. that present in a battery.
why is direct current used in electrlysis and not alternating current
Direct current deposits anions in the anode and cations in the cathode. Incase of an alternating current, the current would keep changing directions and would lead to an uneven distributuion of ions in the electrodes.
Cu2+ forms a
blue precipitate.
products of electrolysis in aqueous solutions
the water molecules dissociate producing H+ and OH- ions
These ions are also involved in the electrolysis process and their chemistry must be considered
We now have an electrolyte that contains ions from the compound plus ions from the water
Which ions get discharged and at which electrode depends on the relative reactivity of the elements involved.
anode (pos) negative ions
cathode (neg)
positively charged ions
products of electrolysis in molten binary compounds
the metal is formed at the negative electrode
the non-metal element is formed at the positive electrode where the negative non metal ions are attracted
Na flame test
yellow-orange
K flame test
lilac
trend in bp in crude oil
longer chains have higher
trend in viscosity in crude oil
longer chains more viscous
trend in flammability in crude oil
longer chain hydrocarbons are less votalie and less viscous than short chains
cracking
Cracking is a technique used in oil refineries whereby large and complex hydrocarbon molecules are broken down into smaller and lighter components that are more useful for commercial or consumer use. Cracking is a critical stage in the process of refining crude oil.
what are structural isomers
Structural isomers are those isomers in which the atoms are completely arranged in a different order with the same molecular formulas. These are the molecules having the same kind of molecular formula with different connectivities depending upon the order they are put together.
homologous series
A homologous series refers to a series of carbon compounds which have a different number of carbon atoms.
functional group
a substituent or moiety in a molecule that causes the molecule’s characteristic chemical reactions.
test for unsaturation
In this test when bromine solution is added to the unsaturated hydrocarbon the brown colour disappears if the hydrocarbon is unsaturated. Bromine forms an addition product with the unsaturated hydrocarbon.
condensation polymerisation
Condensation polymers form in a different way to addition polymers like poly(ethene). Instead of forming just the polymer molecule as the only product, two products form:
a polymer molecule
a small molecule, often water
One type of condensation polymers are polyesters.
biogradeable polymers
a special class of polymer that breaks down after its intended purpose by bacterial decomposition process to result in natural byproducts such as gases (CO2, N2), water, biomass, and inorganic salts.
non-biodegradeable polymers
Non-biodegradable polymers are those polymers that are cannot degraded by microorganisms.
alcohols + sodium
salt + hydrogen
chemical properties of carboxylic acids as those of weak acids
they do not fully dissociate
carboxylic acids react with alochols in the presence of an acid catalyst to produce esters
dissolve in water to form acidic solutions with pH values less than 7
react with metals to form a salt and hydrogen
react with bases to form a salt and water
react with carbonates to form a salt, water and carbon dioxide
compisition of dry air
oxygen and nitrogen
origins of greenhouse gases
.
effects of greenhouse gases
.
origins of gaseous pollutants
.
effects of gasesous pollutatns
.
purpose of chlorine and fluroide ions in the treatment of drinking water
.
greenhouse gases
.
gaseous pollutants
.
what happens when glucose monomers join up to make a polysachharide
they lose water in the condensation reactions.
Hydrolysis is the process of splitting molecules using water.
Polymers can be broken down to produce smaller molecules.
Which of the following is a product of protein hydrolysis?
whichever shows an amino acid
N-H2
C-HR
C=OOH
Why would switching off the circuit between resistance readings improve the quality of results?
As you keep a circuit switched on, more current flows through and this transfers energy to the metal wire by conduction. The wire heats up as a result. This can cause the resistance of the wire to increase. As a result, it makes sense to turn the circuit off and let the wire cool between readings.
Breeders use cell engineering methods to obtain
hybrid cells and growing hybrids from them
origins of greenhouse gases
fossil fuel combustion
effects of greenhouse gases
greenhouse effect
rising temps
ice caps melting
origins of gaseous pollutants
fossil fuel combustion
effects of gasesous pollutatns
myocardial infarction, stroke, heart failure, ecological damage
purpose of chlorine and fluroide ions in the treatment of drinking water
In addition to killing dangerous germs like bacteria, viruses, and parasites, chlorine also helps reduce offensive tastes and odors in water. Furthermore, the chemical helps to eliminate molds, slime, algae, and bacteria that grow in water supply reservoirs, storage tanks, and on the walls of water mains. fluroide helps to pevent tooth decay
greenhouse gases
water vapour
ozone
nitrous oxide
methane
carbon dioxide
gaseous pollutants
carbon oxides
sulphur oxides
nitrous oxides
NO + H2O –>
no reaction as NO is considereed to be thermodynamically unstable
is gold reactive
no extremely unreactive
how does reactiivty impact ease of extraction
The less reactive a metal is the easier it is to extract. This is because lesser reactive compounds can often simply be extracted of their ore with carbon or carbon monoxide,
can carbon displace alumnium
no
When iron oxide is reacted with carbon monoxide to produce iron and carbon dioxide; does the iron undergoes an oxidation reaction
no the iron undergoes reduction; i.e. it gains electrons.
can carbon displace zinc
yes and is therefore able to displace it
disproportionation reaction definition
“the simultaneous oxidation and reduction of the same species in a reaction”
what are heterogenous catalysts
chemical catalysts whose physical phase is different from the physical phase of the reactants and/or products that take part in the catalyzed chemical reaction. Typically, solid phase heterogeneous catalysts are employed in order to facilitate the chemical reaction between two gaseous reactants.
what are homozygous catalysts
catalytic compounds that are in the same phase as the substances which are going into the reaction phase.
