Elements of life

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What are the 3 sub-atomic particles that atoms are made of?
Protons, neutrons and electrons
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What are the charges and masses of these sub atomic particles?
.
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What is the atomic number?
The number of prtons in the nucleus which is numerically equal to the charge on the nucleus
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What is the mass number?
Atomic number + number of neutrons
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What are isotopes?
Atoms of the sae element but with different mass number caused by the number of neutrons being changed
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What is the relative atomic mass (Ar)?
An average of th relativ isotpic masses, taking into account their abundances
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What technique is used to find the atomic mass of elements and compounds?
Mass spectrometry
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What are the 3 key steps to mass spectrometry?
1. Sample is ionised to positively charged cations. 2. Ionare seperated according to their mass (m) to charge (z) ratio (m:z) 3. The seperate ions are then detected with their relaive abundance
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What is the m:z the same as?
The mass of the ion detected
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How can you find the relative abundance of each ion?
From the height of their peak
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How can you calculate the relative atomic mass?
1. Calcuate the average mass of 100 atoms by doing the calculation: (relative isoptic mass x relative abundance) 2. Then divide by 100.
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What was the plum pudding model of the atom and how did Rutherford prove it wrong?
The plum pudding - positiely charged solid sphere w/ negatively charged electrons embedded. Rutherford used the Geiger-Marsden experiment to show that when they fired positive alpha particles at a gold sheet most particles passed straight through
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What is nuclear fusion?
Two light atomic nuclei fuse together forming a single heavier nucleus of a new element, releasing massive quantities of energy.
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What conditions muct there be for nuclear fusion to occur?
High temperatures the nuclei move more quickly and collide with lots of energy so the positive nuclei replusion is overcome
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Give an example of a nuclear fusion reaction:
.
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What is spectroscopy?
The study of how light and matter interact.
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What is Bohr's theory of light?
When an atom is excited, ellectrons jump into higher energy levels. Later they drop back into lower levels, emitting energy as electromagentic radiation & give off an emission spectrum.
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What does an emission spectrum look like?
Black background and coloured lines
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What does an absorption spectrum look like?
Coloured background and black lines
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How is an absorption spectrum created?
When white light is passed through a relatively cool sample of a gaseous element, black lines appear in the otherwise continous absorption spectrum.
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What do the black lines in the absorption correspond to?
The light that has been absorbed by the atoms in the sample: electrons have been raised to a higherlevel and not dropped back down again. The black lines in the absorption spectrum correspond to the coloured lines in the emission spectrum.
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What do the intensity of the lines in the spectrum represent?
A measure of the elements abundance
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What are the 4 main points of Bohr's theory? (part 1)
1. The electron in the hydrogen atom exsists only in certain definite energy levels or electron shells 2. A photon of light is emitted or absorbed when the electron changes from one energy level to another
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What are the 4 main points of Bohr's theory? (part 2)
3. the enrgy of the photon is equal to the difference between the two energy levels ΔE 4. Since E= hv it follows that the frequency of the emitted or absorbed light is related to ΔE = hv
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What is the wave theory of light?
Light is a form of electromagetic radiation and so it behaves like a wave with a wave length and frequency and has the same speed of 3.00 x 10^8 which is the same for all types of light and electromagnetic radiation.
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What is the calculation for working out speed of light?
speed of light = frequency x wavelength
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What is the particle theory of light?
Regards light as a stream of tiny packets of energy called photons. The energy of the photon is related to the position of the light in the electromagnetic spectrum for example photons with an energy of 3 x 10^-19 correspond to red light.
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What is the calculation of finding the energy of a photon?
energy of a photon E = planck constant (6.63 x 10^-34) x frequency
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How many electrons are in the first, second, third and fourth electron?
2, 8, 18 and 32
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What are the sub shells?
s, p, d, f
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How many electrons can be held in each sub shell?
s=2 p=6 d=10 f=14
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The sub shells are divided further into orbitals. How many orbitals does each sub shell contain?
S has one s-orbital P has 3 p-orbitals D has 5 d-orbitals and F has 7 f-orbitals
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Orbitals have characteristc shapes. What are the shapes?
s oribitals are sphereical, p orbitals have dumbell shapes
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Electrons in very atom have a spin in one of two directions, Every electron spins at the same rate in either a clockwise or anticlockwise direction. Show how an electrons occupying the same orbital is written: explain what each component represents
.
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Why is the 4s sub shell filled first before the 3d sub shell and why is the 4s sub shell electrons removed first before the 3d sub shells?
The 4s orbital is filled first because 4s orbital is of a lower energy level than 3 d orbital
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How does a period number correspond to the electron in each orbital?
The period number correspnds to the filling of the final orbital. For example period 3 contains sodium whose electronic configuration is 1s2 2s2 2p6 3s1
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What are the 4 blocks in the periodic table called?
s-block p-block d-block and f-block
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Which block contains the reactive metals and which block contains all the non-metals?
Non-metals = p-block and metals = s-block
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What are vertical columns and rows called?
Vertical columns are groups and rows are periods
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What is periodicity?
The occurence of periodic patterns
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What is the pattern of melting an boiling points in period 3 and explain why?
Increases then dramtically decreases fro silicon. This is because the bonds are weaker so are easier to overcome
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What determines the group number?
The number of shells
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What are closed shell arrangements?
Sub shells are fully occupied by electrons and are stable
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What is the equation for workin out moles with mass and molar mass?
Moles = mass / molar mass
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What is the equation for working out moles using concentration and volume?
moles = concenetration x volume (in cm) / 1000
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What is the difference between empirical formula and molecular formula?
Empirical is just the smallest whole number ratio of each element whereas molecular acount for all atoms
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How do you calculate percentage yield?
( actual yield / theoretical yield ) x 100
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Before you do a titration you must work out a standard solution. What is a standard solution?
Any solution that you know the concentration of.
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How do you make a 250cm of 6.00 mol dm standard solution of sodium chloride?
Work out the moles of solute needed by doing (conc x vol) / 1000 then work otthe grams you need by doing mass = moles x molar mass then make up 250 cm by adding distilled water
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Once you have a sample of a known concentration you can then use this to make standard solutions of other concentrations. What is the calculation we use to do this?
(final concentration / initial concentration ) x volume required = volume to use
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Why do we use a titration?
To find out exactly hw much acid is needed to neutralise a quantity of alkali
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What are the 5 main steps of a titration? (part 1 of 2)
1. measure out the alkali using a pipette and put it in a flask with an indicator 2. rough titration to get an idea o the end point by adding acid whilst swirling until there is a colour change and not the reading on the burette
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What are the 5 main steps of a titration? (part 1 of 2)
3. do an accurate titration by running the acid until about 2cm of the end point then add the acid dropwise 4. work out the amount of acid used to neutralise by subtracting the initial reading by the final reading - to find the titre 5. repeat
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What are the main two indicators and what colours do they change to and from?
1. methyl oragne - yellow to red 2. Phenolphtalein - red to colourless
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How can you work out a concentration from a titration?
1. work out the balanced equation 2. work out the moles 3. use concentration =( moles x 1000 )/ volume
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What is ionic bonding?
When ions are stuck togetehr by electrosatic attraction
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What ions do group 1, 2, 6 and 7 make?
Group 1 = 1+ Group 2 = 2+ Group 6 = 2- Group 7 = 1-
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What is an electrostatic attraction and is it strong or weak?
The fore that holds positive and negative ions together - they are very strong
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Sodium chloride is an ionic compound, what is its structure?
Giant ionic lattice
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What are some features of an ionic structure?
conduct electricity when they are leten or dissolved but not solid - because ions are free to move 2. high melting point because of the electrostatic force 3. often soluble - water molecules are polar so are slightly negative so can pull ions away
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What is covalent bonding?
When two atoms share electrons - there is an electronstatic attraction between the positive nuclei and the shared electrons
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What are the typical properties of a molecular substance that is covalently bonded?
Low mp and bp - no giant structure that needs to be broken down as you only have to brek down the intermolecular forces 2. dont conduct electricity - there are no charge carrier 3. insoluble - water moleules are more attracted to each other
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What is a dative covalent bond?
Where the atoms come from one tom and not both atoms
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What are 2 cases where the idea that 8 electrons causes a happy molecule is not the case?
BF3 because there is only 6 and SF6 because there is 12
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Some covalently bonded substances have ginat structures give an example and explain why it can form a giant lattice structure?
Silicon dioxide because each (silicon and oxygen) can form 4 strong covalent bonds
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What are the properites of giant covalent structures?
1. very high melting points 2. hard 3. good thermal conductors 4. wont dissolve 5. cant conduct electricity
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Why is graphite an exception to the "cant conduct electricty"?
Because graphite has carbon sheets, each carbon shares three of its outer shell electrons with 3 other carbon atoms. This leaves a 4th electron to move freely between sheets
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Metals form giant metallic lattice structures too. How?
The metas atoms are delocalised - leaving a positive metal ion. Thepositve metal ions are attracted to the delocalsied negative electrons
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What are the properties of metallic bonding? (part 1 of 2)
High mp - the more electrons the stronger the metallic bonding. Metals can be shaped ad ductile - because there are no bonds holding specific ions togethe. God thermal conductors becuse the delocalised electrons can pass kinetic energy
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What are the properties of metallic bonding? (part 2 of 2)
Good electric conductors because the delocalised electrons are free to move. Metals are insoluble (except in liquid metals) because of the strength of metallic bonds
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What does the molecular shape depend on?
The electron pairs around the central atom
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The type of electron pair affecrs how much it repels other electron pairs. Which type has the most replusion and so produces the biggest angle?
Lone pair - it pushes bonding pairs together
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Methane, ammonia & water all have 4 pairs of electrons around the central atom. However they each have different bond angles. What are the bond angles?
Methane (no lone pairs) 109.5. Ammonia (1 lone pair) 107. Water ( 2 lone pairs) 104.5
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Linear molecules have what bond angle & what structure? Give an example:
180 and 2 electron pairs on the central atom
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Trigonal planar have what bond angle & what structure? Give an example:
120 and 3 electron pairs (no lone pair)
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Bent have what bond angle & what structure? Give an example:
120 and 3 electron pairs ( 1 lone pair)
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Tetrahedral have what bond angle & what structure? Give an example:
109.5 and 4 elecron pairs (no lone pair)
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Trigonal pyramidal have what bond angle & what structure? Give an example:
107 and 4 eletron pairs (1 lone pair)
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Bent (with 2 lone pairs) have what bond angle & what structure? Give an example:
104.5 and 4 electron pairs (2 lone pairs)
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Trigonal bipyramidal have what bond angle & what structure? Give an example:
120 and 90 with 5 electron pairs (no lone pairs)
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Octahedral have what bond angle & what structure? Give an example:
90 with 6 electron pairs (no lone pairs)
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Why does the melting point increase across the periods for metals?
The metal-metal bonds get stronger across a period because metal ion have an increasing number of delocalised electrons and a decreasing ionic radius which leads to a higher charge density
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In period 3 why does sulfur have a higher melting point than chlorine?
Because sulfur exsists as S8 so is the biggest molecule and the more atoms in a molecule means stronger intermolecular forces
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What is ionisation?
The removal of one or more electrons
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What is the first ionisation enthalpy?
The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mol of gaseous 1+ ions
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What are the 3 main things which affect the size of ionisation enthalpies?
Atomic radius-further away the electrons are from the nuclues the less attraction so lower enthalpy. Nuclear charge-more protons attracts electrons so enthalpy will be higher. Electron shielding-inner electrons shield outer electrons so enthalpy lowe
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Why do first ionisation ethalpies deacrease down a group?
Bcause there is less attraction between the nucleus and outer shell electrons (shells are futher from the nucleus, shielding increases)
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The number of protons increases down a group but why does this not increase the ionisation enthalpy?
Its a less important factor than shielding or distance of outer electrons from the nucleus
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Why does the first ionisation enthalpy increase across a period?
The number of protons increases and outer shell electrons stay roughly the same.
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Why do s-block metals have low ionisation enthalpies?
Because they have low nuclear charges (making metals highly reactive)
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Why do p-block metals have higher nuclear charges compared to s-block?
The increase in number of protons so have higher first ionisation enthalpies
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Group 2 metals react with water to produce what?
Hydroxide and hydrogen
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Why do group 2 metals get increasingly more reactive?
The utermost electrons are futher from the nucleus
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What is produced when a group 2 metal is burnt in oxygen?
A solid white oxide
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Group 2 oxides and hydroxides are bases. Give an example of a group 2 metal reacting water and also a group 2 ocides neutralising an acid
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Solubility trends depend on the compound anion. What are the trends of group 2 hydroxides and group 2 carbonates?
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What do group 2 carbonates decompose into? Give an example
CO2 and metal oxides
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What is thermal decomposition?
When a substance breaks down when heated
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Thermal stablity increases down group 2. Why is this?
Futher down the group the larger the cations. Carbonate ions are large anions that can be made unstable by cations. The cation distorts the carbonate ion,the larger the cation the less distortion
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What are salts formed from?
Positve cations and negative anions (when naming you put the cation first)
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What are the salts that are insoluble?
Silver halides, copper iodide, lead iodide, lead chloride, lead bromide, barium sulfate, calcium sulfate, lead sulfate, most hydroxides (exept Li, Na, K, strontium, Ca, barium & ammonium), most carbonates (except Li, Na, K and ammonium)
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Some insoluble carbonates form coloured percipitates. Most carbonates form white colours. What colours do copper and silver carbonates form?
Copper = blue/green. Silver = yellow
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How do you make an insoluble salt using a perciptation reaction?
Pick two solutions which contain the ions you need. For example if you want to mk lead chloride youd mix lead nitrate with sodium chloride and then percipitate the salt out and filter, wash and dry
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How do you make a soluble salt using a metal or insoluble base?
Pick the right acid (to make chlorides use hydrochloric acid) Add the solid metal. Filter out the excess metal. To get pure solid crystals evaporate some water and leave the rest to evaporate slowly (this is crystallisation)
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How do you make soluble salts using an alkali?
With alkalis like ammonium hydroxides you have to add exactly the right amount of alkali to neutralise the acid - use a titration. Once you have found the right amunt you can do the titration again without the indicator, then evaporate to crytalise
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How do you do a flame test?
Dip a nichrome wire loop in concentrated hydrochloric acid, dip it into the compound, hold the loop in a flame.
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What are the colours of these metal ions: Li+, Na+, K+, Ca2+, Ba2+,Cu2+
Crimson, orange/yellow, lilac, brick red, green, blue/green
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How can you use sodium hydroxide as a test for meal ions?
Because insoluble hydroxides have a colour you can add soidum hydroixde to form a colour
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What are the colours of these metal ions when in a hydroxide: silver, caldium, copper (II), lead (II), iron (II), iron (III), zinc and aluminium
Brown, white, blue, white, green, reddish brown, white then colourless, white then colourless
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How is hydrochloric acid used to help detect carbonates?
Carbonates fizz in HCl because they give off carbon dioxide (test for CO2 is limewater, turns cloudy)
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How do you test for sulfates with HCl and barium chloride?
Add these to a substance and if a whiter perciptate of barium sulfate forms then you know the original compound contained sulftae
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How do you use litmus paper and NaOH to test for ammonium compounds
Ammonia gas is alkaline so using a damp piece of litmus paper you can see if the paper turns blue. Also adding NaOH and heating will give off ammmoni
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How do you use litmus paper to test for hydroxides?
It will turn blue
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Wht are the positive results of tetsing halides with silver nitrate solution?
Chloride = white percipitate Bromide = cream Iodide = yellow
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How do we use NaOH and aluminium to test for nitrates?
Warm solution with NaOH and aluminum. The aluminum reduces the nitrate ion to ammonium iions. The ammonum ions then react with the OH ions to produce ammonia gas
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Diagram of the electromagentic spectrum:
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Riri2019

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some spelling mistakes but otherwise good resource

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