Elements of Life Flashcards
What is the atomic number?
The number of protons in the nucleus of an atom
What is the mass number?
The total number of protons and nuetrons in the nucleus of an atom
What is relative atomic mass (Ar)?
The mass of one atom of an element relative to 1/12 the mass of carbon-12
Is an average of relative isotopic masses, taking into account abundance
What do the different numbers on the nuclear symbol (of an element etc.) tell you?
No. protons = Atomic no. (Bottom no.)
No. electrons = Atomic no. (Bottom no.)
No. neutrons = Mass no. - atomic no.
(Top no. - bottom no.)
Mass no. (Ar) = Top no.
How are models of the atom made + updated?
Tested using experimental investigations
Are revised when observations are made that aren’t predicted by model
What were the different steps/models in the development of the current atomic model?
- Dalton model - simple ‘billiard ball’. Particles cannot be divided, created, or destroyed. Are unique.
- ‘Plum pudding’ model - electrons embedded in sea of positive charge. Discovered by firing cathode rays (electrons) in air - discovered e-. Introduced idea that atoms made of smaller particles
- Nuclear model - Geiger-Marsden experiment showed some alpha particles deflected at large angles by small, dense area of positive charge surrounded by e-
- Bohr model - Evidence from atomic spectra + patterns of ionisation enthaply. e- arranged in shells - ‘planetry model’
What is nuclear fission?
The splitting of a large, unstable isotope triggered by bombarding it with smaller, high-speed particles (usually neutrons)
What conditions are needed for nuclear fission?
Why?
High temps and/or pressure to provide the energy needed to overcome the repulsion between the 2 positive nuclei
What is the nuclear symbol for a neutron?
10n
Except with the 1 and 0 in line above each other…
Write a nuclear equation for the fusion of a 11H nucleus with a 21H nucleus
21H + 31H → 42He + 10n
- Ignore the bit in the picture about what reaction it is…*
- Also neutrons only need to be included if numbers don’t add up*
What is the general formula for calculating Ar?
(% abundance of x X isotopic mass of x) + (% abundance of y X isotopic mass of y)
/ 100%
The Ar of potassium is 39.1. Calculate the relative abundance of 39K and 41K
Make 1 isotope abundance x so the other = 100-x
(39x + 41(100-x))/100% = 39.1
Multiply both sides by 100 + multiply out brackets
39x + 4100 - 41x = 3910
-2x = -190, x =95
39K = 95%, 40K = 5%
What are isotopes?
Atoms of the same element with a different number of neutrons
This causes mass number to be different
Their relative abundances are used to calculate Ar
What is Mr?
Relative molecular mass
The ratio of the average mass of one molecule of an element or compound to one twelfth of the mass of an atom of carbon-12.
(Ar but for molecules… (not elements))
What is the Avogadro constant (NA)?
The number of atoms/molecules in 1 mole of a substance
What does quantised mean?
Energy that can only take particular values (known as quanta)
What is the ground state?
The lowest energy level that an electron can occupy
What is a photon?
Quanta of energy in the form of electromagnetic radiation
Breifly describe Bohr’s model of the atom
Electrons in an atom occupy discrete, quantised energy levels/shells
Electrons in an energy level have a specific amount of energy
Hence the energy of the electron is said to quantised
What property does light have?
What does this mean?
Wave-particle duality
Means it can behave like both a wave and a particle…
What properties does light have the mean it can be described as a particle?
Made up of ‘tiny packets of energy’ called photons
The energy of a photon corresponds to its position in the EM spectrum
Increased freq. = increased energy + decreased wavelength
What equation links the wave + particle models of light?
ΔE = hv
ΔE = energy of photon (J) h = Planck's Constant v = frequence (Hz/s<sup>-1</sup>)
What equation expalins the wave properties of light?
c = vλ
c= speed of light (ms<sup>-1</sup>) v = frequency (Hz/s<sup>-1</sup>) λ = wavelength (m)
Describe the appearance of an emission spectrum
Consists of coloured lines on a black background
The lines become closer at higher frequencies
There are several series of lines (although some may fall outside visible part of spectrum)
What is spectroscopy?
The study of how light and matter interact
Uses IR, visible, and UV light
Explain the formation of an emission spectrum
- Electrons in the ground state absorb energy
- This promotes them to a higher energy level - excited state
- Electrons then drop back down to lower energy levels. The energy lost (ΔE) us emitted as a photon of light
- The frequency of the photon is related to the energy lost by ΔE = hv
- Different energy gaps produce photons of different frequencies
- This produces different coloured bands on the emission spectrum
Why can emission/absorption spectra be used to identify different atoms from a compound/mixture?
Because each element has a unique configuration of electrons, therefore has a unqiue emission/absorption spectrum
The energy levels of the electrons are discrete + quantised means only certain freqs. emitted/absorbed - it’s not continuous
What are flame tests?
Used to identify the presence of specific metals in a sample
Different metals give different coloured flames depending on their emission spectra
What is flame colour?
The light emitted by metal ions when a vaporised metal salt is heated up in a flame
What colour flame does Li+ give?
Bright red
What colour flame does Na+ give?
Yellow
What colour flame does K+ give?
Lilac
What colour flame does Ca2+ give?
Brick red
What colour flame does Ba2+ give?
Apple green
What colour flame does Cu2+ give?
Blue-green
Describe the appearance of an absorption spectrum
If white light is passed through a sample of vaporised atoms, an absorption spectrum is seen
Shown by black lines on a rainbow background (showing all colours of visible light)
How are atomic absorption spectra formed?
- Electrons in the ground state absorb photons of light
- The energy from these photons causes the electrons to be excited to higher energy levels
- The electrons drop back down to the ground state and a photon/light is emitted
- The energy of this photon is related to the frequency/energy of light initally absorbed as ΔE = hv
- Light of the frequency doesn’t pass through the sample (as it’s absorbed) so a black line is seen in the spectrum
What are the similarities between emission and absorption spectra?
For a given element, lines appear at the same frequency
Lines converge at a higher frequency
Several series of lines are seen
What are the differences between atomic emission and absorption spectra?
Emission spectra show coloured lines on a black background
Absorption spectra show black lines on a coloured background
Why do the lines of emission/absorption spectra get closer together at higher frequencies?
Higher frequency lines are caused by translations of electrons with large ΔE values
These are produced from translations from higher energy levels
Higher energy levels are much closer together than lower energy levels
Translations from adjacent energy levels will have similar ΔE values and hence produce light of similar frequencies
Why are several series of lines seen on emission/absorption spectra?
Lines are produced when electrons drop to a lower energy level
Different series of lines are produced by electrons dropping to different ground states/electron energy levels
What is the principle quantum number?
Shell
Given as n (i.e. 1,2,3 etc. the number before the letter…)
The higher the value, the higher the energy
What are shell divided in to?
Sub-shells
Labelled s, p, d, and f
What is each sub-shell divided into?
What are its properties?
Atomic orbitals
Each can hold max of 2 electrons
These electrons must have opopsite (or paired) spinds
Represented by boxes. Arrows drawn in them represent electrons
How many orbitals does the s sub-shell contain?
1 s-orbital
Summarise the way in which electrons are organised in atoms, starting with the largest grouping.
Shell/PQN
Sub-shells
Atomic orbitals
Draw the different shapes of the p orbital
px-orbital
py-orbital
pz-orbital
How many orbitals does the p sub-shell have?
3
How many orbitals does the d sub-shell have?
5
How many orbitals does the f sub-shell have?
7
What are the rules that determine the distribution of electrons in atomic orbitals?
The orbitals are filled in order of increasing energy
Where there is more than one orbital at the same energy, the orbitals are first occupied by a single electron. When each orbital is singly occupied, the electrons pair up in the orbitals
Electrons in singly occupied orbitals have parallel spins
Electrons in doubly occupied orbitals have opposite (paired) spins
What are the 2 ways of representing electron distribution?
By writing out the electronic configuration in full
e.g. 1s22s22p5
By drawing the electronic configuration in boxes…
(see picture)
Draw a diagram to show the shape of the s-orbital
It’s a ball shape
On the periodic table what is a period?
A row
What is periodicity?
The occurence of a regular pattern in a property as you go across a period
The regular pattern is also repeated in other periods
How are elements in the periodic table arranged?
How did they used to be arranged?
Arranged by atomic number (no. protons)
Used to be arranged by Ar
What trend do melting/boiling points follow across a period?
(e.g. period 3)
Melting point increases then decreases across the period
This is because the metals on the left-hand side of a period are metalically bonded so have higher melting points due to the deloclaised electrons between nuclei. The further across the period, the more electrons and the more positive the nucleus becomes, so the stronger the bonds.
Silicone has a high melting point because it is a giant covalent structure which requires a lot of energy to break
The remaining non-metals are simple molecules. They are only held together by weak intermolecular forces (e.g. id-id). The melt these molecule you don’t need to break the strong covalent bonds, only the weak intermolecular bonds.
What is first ionisation enthalpy?
The energy needed to remove one electron from each atom in one mole of isolated gaseous atoms of an element
What is the general equation for first ionisation enthalpy?
X(g) → X+(g) + e-
Remember state symbols!
What is the trend in first ionisation enthalpies as you go across a period?
Why?
First ionisation enthalpy increases across a period.
Group 0 elements have the highest values because they have full outer shells, making it difficult to remove an electron
First ionisation enthalpy is lowest for Group 1 elements because they have only 1 outer shell electron which is relatively easy to remove/ionise
First ionisation enthalpy increases across a period because the number of protons in the nucleus increases, meaning the electrons are more strongly attracted to the nucleus so are harder to remove
What is the trend in first ionisation enthalpy down a group?
Why?
First ionisation enthalpy decreases down a group
This is because electrons are in shells that are further away from the nucleus, thus the attraction between the two is less (electron shielding)
What is the trend for atomic radii across a period?
Decreases due to the increased number of protons
This means there is greater attraction between the outer electrons and the nucleus
What is a closed shell?
When all sub-shells are fully occupied by electrons
Why are s-block elements more reactive than p-block elements?
Because the formation of M+ or M2+ ions only requires input of energy equivalent to the first/second ionisation enthalpy.
For p-block elements greater input of energy is needed to lose eletrons due to the greater electron affinity as a result of a more positive nucleus
What is a dative covalent bond?
A type of covalent bond in which both electrons come from the same atom
Show by arrow pointing away from donor
What is a lone pair?
A pair of electrons in the outer shell of an atom that are not involved in bonding
What is ionic bonding?
Bond formed between metal + non-metal atom
Metal transfers/donates electron(s) to non-metal atom
This results in formation of charged ions, often with full outer shells. This makes them particularly stable
Draw a dot-and-cross diagram to show the formation of NaCl from Na and Cl
Note: You only need to show outer shells + don’t have to draw circles
(Also don’t need the arrow, should be written like an equation)
How are individual ions held together to form ionic compounds?
Cations + anions produced by ionic bonding held together by electrostatic attraction between each other
Results in the formation of a giant ionic lattice
What is covalent bonding?
Bonding that occurs between 2 non-metal atoms
Formed by the atoms sharing one or more pairs of electrons
(If 2 pairs shared, double bond formed, etc.)
Draw diagrams to show the different ways in which dative covalent bonds can be represented
Can be represented by:
Dot-and-cross diagrams
Arrow (in structural formulae)
How are the atoms in a simle covalent bonds?
There is an electrostatic attraction between the positive nuclei of the 2 atoms and the shared pair of negative electrons in the bond
This is greater than the repulsion between the 2 nuclei
What is electron pair repulsion theory?
(AKA VSEPR - Valance Shell Electron Pair Repulsion)
States that the shape adopted by a simple molecule is that which keeps repulsive forces to a minimum.
All bond angles must add up to = 360º
Describe/explain how electron pair repulsion determines the shape of molecules
Electron pairs/groups repel each other
They will arrange themselves to get as far apart as possible
State the no. total pairs of electrons
State the no. bondind pairs/groups of electrons
(if applicable) state the no. lone pairs
(if applicable) lone pairs repel more than bonding pairs (decrease bond angle by 2.5º each)
This creates the shape […] with the angle(s) […]
When describing/explaining electron pair repulsion in double/triple bonds, how should you describe electrons?
As groups not pairs
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Linear
180º
2 pairs of electrons (all bonding)
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Triangular planar
120º
3 pairs of electrons (all bonding pairs)
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Tetrahedral
109.5º
4 pairs of electrons (all bonding pairs)
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Trigonal Bipyrimidal
90º and 120º
5 pairs of electrons (all bonding pairs)
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Octahedral
90º
6 electron pairs (all bonding)
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Pyrimidal
107º
4 pairs of electrons
3 bonding pairs
1 lone pair
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Bent (or V-shaped)
104.5º
4 electron pairs
2 bonding pairs
2 lone pairs
Give the shape and bond angle of the molecule shown in the picture
State how many bonding pairs/pairs of electrons there are in the molecule
Bent (or V-shaped)
118º
3 electron groups
2 bonding groups
1 lone pair
How do double/triple bonds affect the number of bonding electrons?
Can be thought of as a single group of electrons
e.g. CO2 has double 2 double bonds (4 electron pairs in total) which can be thought of as 2 electron groups
What type of structure do ionic bonds have?
Always giant ionic (lattice)
What type of structure do covalent bonds have?
Either simple molecular or giant covalent network
What type of structure do metallic bonds have?
Always giant metallic lattice
Describe the structure of a giant ionic lattice
Has a regular repeating pattern of postivitely and negatively charged ions in all 3 dimensions
The attraction between these oppositely charged ions outweighs the repulsion between ions with the same charge becayse the oppositely charged ions are closer
What are the characteristic properties of giant ionic lattices?
High melting point because of strong electrostatic attractions between ions
Often soluble in water (due to charges of ions)
Conduct electricity when molten/in solution as charged ions able to move in response to voltage
Describe the structure/bonding in simple molecular covalent bonding
Strong covalent bonds within molecules (between atoms) (strong intramolecular bonds)
But only weak intermolecular bonds between molecules
What are the characteristic properties of simple covalent molecules?
Low melting point
Usually insoluble in water
Do not conduct electricity (or heat)
Describe the structure/bonding in a giant covalent network
Contain billions of atoms with strong covalent bonds between them
What are the characteristic properties of giant covalent networks?
High melting point because all bonds in structure are strong covalent bonds
Insoluble in water
Do not conduct electricity (apart from graphite)
Describe the structure/bonding in a giant metallic lattice
All metals/metalic bonds have giant metallic lattice structure
Has a strong electrostatic attraction between the positive metal ions and the delocalised electrons between the ions
What are the characteristic properties of giant metallic lattices?
High melting point because there is strong electrostatic attraction between ions + electrons
Insoluble in water
Conduct electricity when solid/molten because delocalised electrons are free to move in response to voltage
What are delocalised electrons?
Electrons that are not associated with a particular atom
Instead are free to move over several atoms
In the giant ionic lattice/crystalline structure of NaCl, 6 Cl- atoms arrange themselves around 1 smaller Na+ atom
The Cl- atoms arrange themselves to be as far apart as possible. Suggest the name for the 3D arrangement they will take up
Octahedral
Group 1 metals have relatively low melting points
Use ideas about the charge and size of Group 1 ions to explain this
Group 1 ions have a small (+1) charge and have a relatively small ionic radius (compared with other ions in same period)
These 2 factors reduce the electrostatic attraction between the ions and delocalised electrons
They also only have 1 outer shell electron which can become delocalised, meaning electrostatic forces of attraction between ions and electrons are smaller
What is electron affinity?
Energy change when 1mol gaseous atoms aquires 1mol electrons from 1mol gasous anions
What is a complex ion?
Ion containing more than 1 atom
Charge is spread across whole ion
Contains covalent bonds
What is a precipitate?
A suspension of solid particles fromed by a chemical reaction in solution
What is a precipitation reaction?
Reaction between ions in solution that forms a precipitate
(suspension of solid particles/insoluble solid particles)
What does the prefix -ate tell you about the composition of an ion?
There are 1+ non-metal ions/atoms bonded to oxygen
e.g. sulfate -SO42-
What charge does the ClO ion have?
-1
What is the formula + charge of a phosphate ion?
PO43-
What charge does a lead ion have?
Pb2+
What charge does a nitrate ion have?
NO3-
What happens when ionic substances dissolve into solution/water?
The ions become surrounded by water + spread throughout the solution
They behave independantly of each other
Which ionic substances are soluble?
All compounds containing…
Group 1 metals
Nitrate ions
Ammonium ions
… are soluble
Which ionic substances are insoluble?
Sulfates of Ba, Ca, Pb, and Ag
Halides of Ag + Pb
All carbonates except those of Group 1/ammonium ions
Hydroxides containing some Group 2, Al, or d-block ions
Give the colour of precipitate (if one forms) that forms from the reaction of OH- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - White ppt
Ba2+ - White ppt
Cu2+ - Pale blue ppt
Fe2+ - Green ppt
Fe3+ - Brown ppt
Al3+ - White ppt
Pb2+ - White ppt
Zn2+ - White ppt
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of SO42-- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - White ppt
Ba2+ - White ppt
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - White ppt
Zn2+ - Soluble
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of CO32- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Pb2+, Zn2+, and Ag+
Ca2+ - White ppt
Ba2+ - White ppt
Cu2+ - Green ppt
Fe2+ - Green ppt
Pb2+ - White ppt
Zn2+ - White ppt
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of Cl- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - Soluble
Ba2+ - Soluble
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - White ppt
Zn2+ - Soluble
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of Cl- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - Soluble
Ba2+ - Soluble
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - White ppt
Zn2+ - Soluble
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of Cl- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - Soluble
Ba2+ - Soluble
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - White ppt
Zn2+ - Soluble
Ag+ - White ppt
Give the colour of precipitate (if one forms) that forms from the reaction of Br- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - Soluble
Ba2+ - Soluble
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - White ppt
Zn2+ - Soluble
Ag+ - Cream ppt
Give the colour of precipitate (if one forms) that forms from the reaction of I- ions with:
Ca2+, Ba2+ Cu2+, Fe2+, Fe3+, Al3+, Pb2+, Zn2+, and Ag+
Ca2+ - Soluble
Ba2+ - Soluble
Cu2+ - Soluble
Fe2+ - Soluble
Fe3+ - Soluble
Al3+ - Soluble
Pb2+ - Yellow ppt
Zn2+ - Soluble
Ag+ - Yellow ppt
The presence of which ions can be tested for by adding barium chloride solution?
(Solution containing Ba2+ ions)
Sulfate (SO42-) ions - white ppt formed
The presence of which ions can be tested for by adding silver nitrate solution (containing Ag+ ions)?
Shows presence of halide ions
White ppt forms for Cl-
Cream ppt forms for Br-
Yello ppt forms for I-
What are the 4 ways/reactions that can be used to make an ionic salt?
Acid + base/alkali → Salt + Water
Acid + Carbonate → Salt + Water + CO2
Acid + Metal → Salt + Hydrogen (MASH)
Give three examples of practical applications of precipitation reactions
Water treatment
Production of coloured pigments for paints/dyes
Identification of certain metal ions in solutions
What is relative isotopic mass?
The mass of one atom of an isotope compared to 1/12 of the mass of a 12C atom
(The same as Ar but for isotopes…)
What is empirical formula?
The simplest ratio of atoms in a compound
What is water of crystallisation?
Number of water molecules contained in an ionic lattice per molecule of salt
(i.e. how hydrates the salt is)
Hydrates cobalt (II) chloride has the formula CoCl2•xH2O
1.173g of hydrated cobalt chloride is heated to drive off the water of crytallisation. The mass remaining is 0.641g.
Calculate the formula of the hydrated salt
Calculate the mass of water removed:
1.173 - 0.641 = 0.532g
Calculate the moles of water removed:
0.532 / 18 = 0.02956mol
Calculate the moles of anhydrous salt:
0.641 / 129.9 = 0.00493mol
Calculate the ratio
- *moles water / moles anhydrous salt** =
0. 02956 / 0.00493 = 5.996 = 6
Calculate the percentage by mass of nitrogen in ammonium sulfate (NH4)2SO4
Calculate the Mr of (NH4)2SO4 = 132.1
Calculate the mass of N in 1 mol (NH4)2SO4:
14 x 2 = 28
% by mass = mass element in 1mol / Mr compound x 100
(28/132.1) x 100 = 21.2%
What is the formula for percentage yield?
(Experimental yield / theoretical yield) x 100
Yield given by moles of reactants/products from balanced equation
Why might percentage yield be lower than expected?
Loss of product from reaction vessels (when transfering)
Side reactions (may create by-products)
Impurities in reactants
Changes in temp + pressure (may effect equilibrium)
If the reaction is an equilibrium system
What are the 3 main factors that affect 1st ionisation enthalpy?
Atomic radii - larger = lower
Nuclear charge - more protons = higher
Electron shielding - outer shells feel less electrostatic attraction to nucleus
How do group 2 metals react with water?
Group 2 metal + Water → Metal hydroxide + Hydrogen
M(s) + 2H2O(l) → M(OH)2(s) + H2(g)
How does the vigourousnes of Group 2 metals change as you go down the group?
The reactions become more vigorous as you go down the group
How do the hydroxides of Group 2 metals change as you go down the group?
Become increasing soluble and more alkaline
How do Group 2 metals react with oxygen (when heated)?
Metal + Oxygen → Metal oxide
2M(s) + O2(g) → 2MO(s)
What substances do Group 2 metal oxides react with?
What property does this give them?
They react with acids, so can act as bases
Metal oxide + Acid → Salt + Water
MO(s) + H2SO4(aq) → MSO4(aq) + H2O(l)
How do metal hydroxides react with acids?
Metal hydroxide + Acid → Salt + Water
M(OH)2(s/aq) + 2HCl(aq) → MCl2(aq) + 2H2O(l)
What happens to Group 2 metal carbonates when they are heated?
Give the general equation
Undergo thermal decomposition
Metal carbonate → Metal oxide + Carbon dioxide
MCO3(s) → MO(s) + CO2(g)
How does the thermal stability of Group 2 carbonates change going down the group?
As you go down the group, thermal stability increases
Means that metals further down decompose at higher temperatures than those further up the group
Why does the thermal stability of Group 2 carbonates increase as you go down the group?
M2+ ions get larger as you go down the group, so their charge density is lower
Because ions higher up the group have greater charge densities, they polarise the carbonate ion more
The more polarised the carbonate ion, the more likely it is to break up + form an oxide ion and CO2
What is a polarised ion?
A large (complex) ion that can have its electron distribution altered by small, highly-charged ions
This is known as polarisation
What is charge density?
The charge of an ion relative to its size
Mg2+ has a greater charge density than Ba2+ because, although they both have the same overall charge, Mg2+ is smaller
10.0cm3 of a 1.00moldm-3 solution of HCl was transfered to a volumetric flask and made up to 250cm3 with water.
What is the concentration of the diluted solution?
Calculate the dilution factor:
10/250 = 0.04
Use this to calculate the new conc. of the diluted solution:
0.04 x 1.00 = 0.0400moldm-3
What is an acid?
A substance that produces/donates H+ ions in a solution
What is a base?
A copound that reacts with an acid to produce water and a salt
Is a proton acceptor
What is an alkali?
A soluble base
Dissolves in water to produce hydroxide (OH-) ions
What is an oxonium ion?
What is its formula?
H3O+(aq)
Hydrogen ion bonded to a molecule of water
Created due to presence of H+ in acidic solutions (hence present in all acidic solutions)
Briefly describe how a soluble salt can be made
By reacting the appropriate acid and alkali together
The solid salt can then be produced by evaporating the excess solution/water
Breifly describe how an insoluble salt can be made
By a precipitation reaction
E.g. silver iodide can be made by reacting silver nutrate + potassium iodide
