Chem Flashcards
Diameter of nucleus compared to diameter of atom
less than 1/20000 that of an atom
Energy shells around nucleus
Concentric circles
How to find number and abundances of isotopes of an element
Mass spec
Mass spec graph
X axis - m/z
Y axis - relative abundance
Reactivity trend - group 1/2
Reactivity increases
Reactivity trend - group 6/7
Less reactive
Lithium with cold water observations
- slow
- floats but does not melt
- dissolves to form alkaline solution of LiOH
- hydrogen gas
Sodium with cold water observations
- more strongly than lithium
- moves around surface + melts + quickly dissolves
- alkaline solution of NaOH
Potassium with water reaction
- moves rapidly on the surface
- very quickly dissolves to produce an alkaline solution of KOH
Period number…
Number of shells
Group number…
Number of outermost electrons
Lithium
Li+
Sodium
Na+
Potassium
K+
Magnesium
Mg2+
Calcium
Ca2+
Barium
Ba2+
Aluminium
Al3+
Copper (II)
Cu2+
Silver
Ag+
Zinc
Zn2+
Sulfide
S2-
sulfuric acid
H2SO4
ethanoic acid
CH3COOH
buckminsterfullerene
C60
nitrogen
N2
acid + carbonate ionic
2H+(aq) + CO32−(aq) → H2O(l) + CO2(g)
Acid + ammonia ionic
H+(aq) + NH3(aq) → NH4+(aq)
Avagadros symbol
NA (a is subscript)
Avogadros number
6.022 × 1023 mol−1
Define concentration
measure of the number of solute particles in a given volume of solution.
Saturated solution
no more solute will dissolve at a given temperature.
Gases + solubility + temp
gases become less soluble as temperature increases
Reasons % yield not 100
the reaction will not go to completion if it is reversible
some of the product may be lost when it is separated from the reaction mixture
some of the reactants may also react in ways different to the expected reaction.
Oxidation
Gain of oxygen or LOSS OF HYDROGEN
Oxidation states in H2O2
oxygen atoms have an oxidation state of −1
Oxidation states in OF2
oxygen atom has an oxidation state of +2.
Oxidation state of hydrogen
always +1.
The exception is when hydrogen is part of a metal hydride, for example MgH2, and in this case the hydrogen atoms have an oxidation state of −1.
Giant covalent properties
Very high melting and boiling points
Why do giant covalent have a high melting + boiling point
all of the strong covalent bonds have to be broken
Graphite
Soft + conducts electricity
Melting point of simple covalent
Low
Order of group 1 - going down
Trend in boiling points - 1
Decrease
Trend in densities- 1
Increase
Trend in hardness - 1
Decrease
How to prevent group 1 reacting
stored in oil
Metal + water
Metal hydroxide + hydrogen
The metal hydroxide is…
Soluble = makes solution alkaline
2K(s) + Cl2(g)
2K(s) + Cl2(g) → 2KCl(s)
Group 17 order
F2
Pale yellow gas
Why does boiling point decrease down 1
distance of the delocalised electrons to the 1+ ion core within the metallic solid will increase as the ions get larger, causing a decrease in the metallic bond strength.
Iodine colour when displaced
Brown liquid
Bromine is more reactive than iodine. Bromine can…
OXIDISE an iodide ion because it REMOVES an electron
Trend in boiling points - 18
Low anyway - increases down group
Why do densities increase down group
increasing mass of the atoms.
Separating funnel use
to separate two immiscible liquid
Upper layer on separating funnel
Lower density
Purpose of narrowing walls on separating funnel
make it easier to close the tap the moment the last drop of the lower layer has passed through
Fractional distillation use
to separate miscible liquids (ones soluble in each other)
Why does the spot need to be above the solvent line in chromatography
so that it spreads up with the rising solvent rather than dissolves in the solvent at the bottom
Why lid on chromatography
ensure that the atmosphere in the tank has a saturated solvent vapour.
This prevents the solvent evaporating from the paper rather than rising.
What is centrifugation
used to separate heterogeneous mixtures based on their differences in particle mass
How does centrifugation work
If a liquid is mixed with a solid, the solid particles to settle to the bottom of a container as they are more dense than the liquid.
When the solid is small or finely divided, random motion and collisions of the particles causes them to settle much more slowly and in some cases they do not settle to the bottom.
Centrifugation encourages settling by spinning the mixture at high speed in a horizontal circle. As the mixture is spun, the heavier particles are brought to the end of the tube. The heaviest particles settle out first, becoming a pellet at the bottom of the tube.
The remaining liquid may be pure, a solution or still contain small solid particles. The remainder, called the supernatant may be decanted into a new tube and spun again at a higher speed to separate the smaller particles.
Remainder from centrifugation
supernatant
If the single solid component is wanted
decantation, filtration or centrifugation can be used.
Gas-gas mixtures can be separated by…
centrifugation or cyrogenic distillation.
Define acid
ability to donate H+ ions
Salt definition
compound formed when the hydrogen ions in an acid are replaced by metal ions (or other cations)
Reactions between metals and acids will only occur if…..
the metal is more reactive than hydrogen.
Explain why silver sulfate cannot be prepared by adding silver metal to dilute sulfuric acid.
Silver is less reactive than hydrogen, so no reaction will take place under standard conditions.
Weak acid
Carboxylic acid
SO2(g) + H2O(l)
SO2(g) + H2O(l) → H2SO3(aq)
2NO2(g) + H2O(l) →
2NO2(g) + H2O(l) → HNO3(aq) + HNO2(aq)
Concentration 0.10
pH 1
Concentration 0.01
pH 2
Monoprotic acids
HCl, HNO3 and CH3COOH
- only able to donate one acidic H+(aq) ion per acid molecule.
HCl(aq) → (monoprotic)
HCl(aq) → H+(aq) + Cl−(aq)
Diprotic
H2SO4(aq) → 2H+(aq) + SO42−(aq)
donate two acidic H+(aq) ions per acid molecule.
Triprotic acid
H3PO4(aq) → 3H+(aq) + PO43−(aq)
can donate three acidic H+(aq) ions per acid molecule.
Define base
can accept H+ ions, or one that has the ability to form OH−(aq) in solution.
Weak base
Ammonia
Strong base
sodium hydroxide and potassium hydroxide
Cu(OH)2 is basic - why can’t form alkaline solutions
insoluble
Neutralisation
Exothermic
Why neutralisation is exothermic
there is no bond breaking (endothermic)
Iodine clock
time taken for the starch indicator to form a blue-black colour with iodine, I2, is measured = proportional to the initial rate of reaction.
10 degree increase
In many reactions, an increase in 10 °C will approximately double the rate of reaction as approximately twice as many particles will have sufficient energy to react.
endothermic
melting of ice and
the boiling of water
Bind energies only apply
When a gas
Limitations of bond energies
- average values
- can only be done for reactions which take place entirely in the gaseous state.
Assumptions in calorimetry - in aqueous solution
- the density of solution is 1.00 g cm−3
- SHC of solution is that of water
- only the water has absorbed any heat and that the calorimeter does not absorb any energy
Calorimeter material
Polystyrene = insulator = prevent heat loss to surroundings
Calorimetry in combustion experiments
fuel is placed in a burner and when lit, the energy is used to heat water contained in a copper calorimeter.
Calorimetry in combustion experiments - assumptions extra q
Incomplete combustion can be a problem
Heat loss to the surroundings is more likely in this open system
Heat is lost to the calorimeter = conductor
Electron movement in electrolysis
from the positive electrode to the negative electrode.
Fractional distillation crude oil
- vaporised
- passed into the bottom of a long column (a fractionating column) which is hot at the bottom and cool at the top
- different component molecules of the vapour rise until they reach a point where the temperature is below their boiling point; here they condense, and the liquid is run off.
Small hydrocarbons
Low boiling point
Very volatile
Flow easily
Ignite easily
Large molecules
High boiling point
Not very volatile
Do not flow easily
Do not ignite easily
Viscous meaning
do not flow easily
Larger molecules
more viscous (do not flow easily) and are less flammable.
Second stage of refining
catalytic cracking.
catalytic cracking.
longer chain molecules are passed over a heated catalyst and are broken down into shorter chain molecules
Random
two main types of condensation polymers
polyesters and polyamides.
Ester forms from
carboxyl group of a carboxylic acid combines with a hydroxyl group of an alcohol
Amide linkage
carboxyl group of a carboxylic acid combines with an amine group, -NH2.
Proteins
formed from long chains of amino acids joined by amide linkages
Biodegradable polymers
down (degrade) after their intended use to produce such natural products as: CO2, N2, H2O
often contain ester or amide linkages.
Non-biodegradable polymers
not broken down after their intended use
tend to consist of long chains of carbon and hydrogen atoms
= strong bonds
Na + water vs Na + alcohol 🍺
When sodium is added to water, the reaction is fast and vigorous
When sodium is added to ethanol the reaction is much slower and more moderate.
Na + alcohol
2Na + 2C2H5OH → 2C2H5ONa + H2
2Na + 2C2H5OH → 2C2H5ONa + H2 = products
Sodium ethoxide
Sodium ethoxide
Strong alkali
Carboxylic acids
monoprotic
Reaction between carboxylic acid + alcohol 🥃
Reversible + water gone
Carboxylic acid + alcohol conditions
Concentrated sulfuric acid catalyst
Ester naming
first part of the name comes from the alcohol and the second part of the name is the salt of the carboxylic acid
Metal reactivity
Most reactive - group 1 (only one electron needed to go)
Then 2 = process of losing 2 electrons requires more energy
3 = even more energy needed
Transition metals are the least reactive
Iron
Fe2+ and Fe3+
Reactivity metals
Reactivity metals
Positive Electrode (anode) = aqueous
If halide ions (Cl-, Br-, I-) and OH- are present then the halide ion is discharged at the anode, loses electrons and forms a halogen (chlorine, bromine or iodine)
If no halide ions are present, then OH- is discharged at the anode, loses electrons and forms oxygen
Negative Electrode (cathode) - aqueous
If the metal is above hydrogen in the reactivity series, then hydrogen will be produced and bubbling will be seen at the cathode
This is because the more reactive ions will remain in solution, causing the least reactive ion to be discharged
Extract metals
NEEDS TO BE REDUCED
How to extract metal x with carbon
Metals below carbon can be extracted from their ores by reduction using carbon or carbon monoxide, such as iron from iron ore (haematite) in a blast furnace.
BECAUSE CARBON IS MORE REACTIVE + CAN DISPLACE
When to use electrolysis to extract metal
When more reactive then carbon
Displacement reactions of metals
occur when a more reactive metal is added to a dissolved compound of a less reactive metal
Why does Mg + H2SO4 → MgSO4 + H2 happen but Cu + H2SO4 → no reaction happens
magnesium is above hydrogen in the reactivity serie = can displace
copper is below hydrogen in the reactivity series = can’t displace
Aluminium
silvery-white, lightweight
soft and malleable
corrosion resistant and non-toxic,
Low density
Electrical conductor
cans, kitchen foil and utensils
Iron pure
Soft
High carbon steel
strong but brittle and is used in cutting tools and drill bits.
Low carbon steel
softer and more easily shaped, and is used in car bodies.
Where does steel come from
Impure iron is purified and then mixed with controlled amounts of carbon to produce steel which is strong, malleable (can be shaped) and ductile (can be drawn into wires)
Copper
- good conductor
- ductile
- malware
- strong
- unreactive
- wires
- cooking
Silver
Best thermal / electrical conductor
- jewellery
- lustre
- antimicrobial
Gold
- soft
- heavy metal
- ductile
- malleable
- conductor
Titanium
As strong as steel but less dense
- aircraft
desired properties for a hip replacement
high strength, low density, corrosion resistance and biocompatibility.
How do the properties of transition metals differ from Group 1 elements?
Compared to Group 1 metals, transition metals have high melting points and boiling points. They are also strong, hard and unreactive. Transition metals often form coloured compounds and form ions of different charges that enable them to be used as catalysts.
Hydrogen
- burning splint = produces water = goes out with a squeaky pop
Oxygen
Glowing splint / burning splint is blown out to leave red glowing embers
Splint relights
Carbon dioxide
Calcium hydroxide to form calcium carbonate
Chlorine
piece of damp blue litmus or indicator paper is held in the gas. Chlorine forms an acidic solution in water which turns the litmus red. Chlorine is also a bleach so the red and blue colours will then both fade to leave a white colour
Sulfate
dilute nitric or hydrochloric acid to the unknown solution, followed by a solution of barium nitrate or chloride.
Order
1) Test for the presence of carbonate ions using a dilute acid
2) Test for the presence of sulfate ions using HCl/BaCl2(aq)
3) Test for halide ions using HNO3/AgNO3(aq)
Why is nichrome wire used
Inert / high b.p = do it melt or give visible colour of their own
Lithium - flame test
Crimson red
Sodium - flame test
Yellow - orange
Potassium - flame test
Lilac
Calcium - flame test
Red-orange
Copper - flame test
Green
Solubility of metals
Increases down group
Mg 2+ sodium hydroxide precipitate test
White
Ca 2+ sodium hydroxide precipitate test
White
Al 3+ sodium hydroxide precipitate test
White
Cu 2+ sodium hydroxide precipitate test
Blue
Fe 2+ sodium hydroxide precipitate test
Green
Fe 3+ sodium hydroxide precipitate test
Brown
Aluminium hydroxide sodium hydroxide precipitate test
also a white precipitate but this precipitate will dissolve in an excess of sodium hydroxide to leave a colourless solution
testing for Fe2+
green precipitate of Fe(OH)2 that initially forms will turn brown on standing as it oxidises in the air to form Fe(OH)3
Test for water
using solid copper(II) sulfate
white when anhydrous but blue when hydrated
Test for water equation
CuSO4(s) + 5H2O(l) → CuSO4·5H2O(s)
If excess water is added, the copper(II) sulfate will dissolve to form a blue solution, CuSO4(aq).
Quantitative analysis of Sulfate
concentration of the sulfate ions can be found by adding an excess of barium chloride solution.
The precipitate can be filtered, dried and weighed.
The number of moles of barium sulfate can be determined from the mass of dry solid.
From the volume of solution tested, the concentration of sulfate ions can be found.
Nitrogen
N2
N2
78.1
02
20.95
Argon
0.9
Carbon dioxide
0.04 - percentage in dry air
How to separate silicon dioxide and water
Filtration - silicon dioxide can not mix with water because it’s a giant covalent
