Studied by 1 personWhat are the 3 states of matter?
Solid
Liquid
Gas
How are covalent bonds formed?
When 2 non-metals share a pair of electrons
Why does a chemical cell eventually stop producing a voltage?
-It is an exothermic reaction and energy is transferred by electricity -When a reactant is used up, it goes 'flat'
What are some compounds found in fertilisers?
-Nitrogen - NH₄⁺ -Phosphorus PO₄³⁻ -Potassium - dissolve in water to form K⁺ ions
What is the theoretical yield of a reaction?
The maximum amount of a product that can be formed from a reaction
How do you calculate the relative formula mass (Mr) from the relative atomic masses (Ar)?
Ar of all elements added together
What is the symbol for corrosive?
What are some examples of common simple molecular covalent compounds?
-Methane CH4 -Water H2O -Hydrogen Flourine HF -Nitrogen Oxide NO2
What is an elctrolyte?
An ionic substance with freely moving ions (molten or in solution)
How are cations formed?
When electrons are lost
What happens in a reversible reaction?
The reaction can proceed both forwards and backwards
What is the common reaction of metal with water?
metal + water → metal hydroxide + hydrogen
How did Mendeleev arrange elements in a periodic table?
By their properties and atomic mass
Where are transition metals positioned in the periodic table?
The middle
What is the difference between a pure substance and a mixture?
A pure substance is only made up of 1 substance (element or compound) that is chemically bonded. A mixture is made up of elements and compounds that do not react with each other and can be separated with physical processes.
How have Dalton's ideas about atoms changed?
-Dalton thought that atoms were solid spheres that made up all matter and couldn't be created or destroyed. They were the smallest particle. -JJ Thompson discovered the electron in 1904, came up with the 'plum pudding' model-the atom was a solid positively charged sphere with negative electrons placed inside it -Rutherford did alpha scattering experiment in 1911. Fired alpha particles through thin gold foil and discovered atoms have a positively charged nucleus and electrons circle on orbits around it
How are anions formed?
Electrons are gained
What is a chemical cell made up of?
2 metals dipped in their salt solution A 'salt bridge' to allow ions to pass from one to another Voltage produced between metals Current flows when connected to an external circuit
How is ammonium nitrate made using ammonia from the Haber process?
N₂+3H₂ ⇌ 2NH₃ -Pressure of 200 atmospheres -Temp 400-450°c -Iron catalyst
What is the actual yield of a reaction?
The amount of product obtained when you carry out an experiment
How do you calculate the empirical formula of a compound?
-Mass of element/Ar -Divide both by smaller one to find simplest ratio -Find simplest whole number ratio -Write out formula
What is the symbol for irritant?
What changes happen between them?
Solid - liquid = melting Liquid - gas = evaporating Solid - gas = sublimation Gas - solid = deposition Gas - liquid = condensing Liquid - solid = freezing
What are the properties of covalent simple molecular compounds?
-Low melting and boiling point -Poor conductor of electricity -Often gas or liquid at room temperature
How did Mendeleev predict the existence and properties of elements yet to be discovered?
By observing patterns in his periodic table and leaving gaps where patterns didn't match
How are subatomic particles arranged in the nucleus?
-Proton and neutron in nucleus -Electron on outer shells
What is the melting point of a pure substance?
Sharp, will melt at one specific temperature as all particles will change from solid to liquid at the same time because they have the same melting point
What are some physical properties of transition metals?
High melting point High density Malleable Ductile (can be drawn through wire)
What does the symbol ⇌ mean?
It is a reversible reaction
What is the common reaction of metal with acid?
metal + acid → salt + hydrogen
What happens during electrolysis?
Compounds are split up using electricity
What is a molecule?
A group of non-metal atoms joined by covalent bonds
What are the names of some common molecular elements?
Oxygen Hydrogen
What are the main features of a hydrogen-oxygen fuel cell?
-Fuelled by hydrogen and oxygen -Only product is water -Doesn't go 'flat', only stops when no more reactants are supplied -Overall reaction is 2H2(g) + O2(g) → 2H2O(l)
How is ammonium sulfate made on a small scale?
1.Put some dilute sulfuric acid into a beaker. 2.Add a few drops of methyl orange indicator. 3.Add dilute ammonia solution drop by drop, stirring in between. 4.Continue step 3 until the colour permanently changes from red to yellow. 5.Add a few more drops of dilute ammonia solution. 6.Pour the reaction mixture into an evaporating basin, and heat carefully over a boiling water bath. 7.Stop heating before all the water has evaporated. Leave aside for crystals to form. 8.Pour away excess water and leave the crystals to dry in a warm oven (or pat dry with filter paper).
How do you calculate percentage yield of a reaction?
actual yield/theoretical yield x 100
What is the difference between empirical and molecular formula?
-Molecular formula is the actual number of atoms in one molecule of a substance -Empirical formula is the simplest whole number ratio of elements in a compound
What is the symbol for harmful?
Why do covalent simple molecular compounds have low melting and boiling points?
They have weak intermolecular forces that can be broken easily
How were Mendeleev's ideas supported by later evidence?
In 1937 technetium was discovered with a relative atomic mass of 98. Mendeleev had left a gap in the table for an element with relative atomic mass of 98
Why are displacement reactions redox reactions?
redox = reduction and oxdiation happen More reactive metals displace less reactive ones so electrons are transferred, meaning both reduction and oxidation happen
What is the arrangement and movement of particles in a solid?
-Regular placement -Close together -Vibrate around fixed positions
What is the movement of ions in electrolysis?
Cations (+) move to the cathode (-) and gain electrons Anions (-) move to the anode (+) and lose electrons
What is the difference between an atom and an ion?
Atoms are not charged, whereas ions are charged
What is a dynamic equilibrium?
The reaction is happening both forwards and backwards at the same rate, and is dynamic because the chemical reaction is happening constantly and is moving
What is the melting point of a mixture?
Will melt over a range of temperatures
How are atoms of different elements different?
They have different numbers of protons
What are some chemical properties of transition metals?
Form coloured compounds - unlike group 1/2 that form colourless/white compounds Colour of transition metal hydroxide can identify ion present in solution Used as catalysts
How are ions in group 1 formed?
1 electron is lost to form a cation
What are the reactions at the electrodes in a hydrogen-oxygen fuel cell?
Cathode = 2H₂(g) →4H⁺+4e⁻ Hydrogen atoms oxidised to form ions
Anode = 4H⁺(aq)+4e⁻+O₂→2H₂O Electrons flow through circuit to anode and gain electrons and react with oxygen
How is ammonium sulfate made on a large industrial scale?
-Has several stages as ammonia and sulfuric acid have to be made -One method uses a large chamber filled with ammonia gas and sprays sulfuric acid in so it reacts to produce ammonium sulfate
What are some reasons actual yield is less than theoretical yield?
-Reaction may be incomplete -Some product is lost transferring between containers -Unwanted side reactions taking place that use up reactants and turn into other products
How can empirical formula be calculated from percentage of a compound it makes up?
-Write out % -Find moles by dividing %/Ar -Divide both by smallest -Write out
What is the symbol for flammable?
Why are covalent simple molecular compounds bad conductors of electricity?
They have no charge carriers (e.g. electrons) that are free to move and carry a current
What are the names of some common molecular compounds?
Methane CH4 Water H2O Nitrogen Oxide NO2
What is the relative mass and charge of a proton?
Mass = 1 Charge = +1
What mixtures can be separated by filtration?
-Sand and water -Dirt and water
Why does iron have the typical properties of a transition metal?
Malleable High melting point Catalyst used in Haber process
What is ammonia formed of?
NH₃
How do metals high (K, Na, Ca - not acid) on the reactivity series react with water and acid?
water = form hydrogen and metal hydroxide acid = react violently (not Ca)
What is oxidation (in terms of electrons)?
Loss of electrons
What is the arrangement and movement of particles in a liquid?
-Random -Close together -Move around each other randomly
What were some problems Mendeleev had when ordering the elements?
Some elements with similar properties did not fit together in terms of relative atomic mass
What are the formulae and charges of common polyatomic ions?
-Carbonate CO₃²⁻ -Hydroxide OH⁻ -Nitrate NO³⁻
What are different uses of fuel cells?
-Power car - less maintenance and doesn't release CO₂ but can be hard to charge and doesn't make noise so can be dangerous. Hydrogen fuel can be hard to store and it's very flammable so could be dangerous
How does changing the reaction conditions affect the relative amount of substances in an equilibrium mixture?
-Increasing pressure shifts the reaction to the direction with less molecules -Increase temperature shifts equilibrium to backwards reaction -Decrease temperature shifts equilibrium to forwards reaction - particles move more slowly so it takes longer
How is atom economy calculated?
Mr of useful product/Mr of all reactants added x 100
How do you calculate molecular formula from empirical formula and relative formula mass?
-Find Mr of empirical formula -Divide Mr of compound by Mr of formula -Multiply all in formula by answer to get molecular formula
What is the symbol for toxic?
What is the structure of a polymer?
'Chain molecules' made up by linking lots of small molecules called monomers in a long chain
What bonds are found in molecules?
Covalent bonds
What does atomic number mean?
Number of protons in an element
What is reduction (in terms of electrons)?
Gain of electrons
What is the relative mass and charge of a neutron?
Mass = 1 Charge = 0
What is the arrangement and movement of particles in a gas?
-Random -Far apart -Move quickly in all directions
What mixtures can be separated by crystallisation?
-Salt and water
How do metals in the middle (Mg, Al, Zn, Fe) of the reactivity series react with water and acid?
water = very slowly, but react with steam to form hydrogen and a metal hydroxide acid = react to form hydrogen and a salt solution (includes Ca)
What happens in the corrosion of metals as a result of oxidation?
Metal reacts with oxygen in air to form metal oxide Metals form a thin layer of tarnish when they oxidise to stop oxygen reaching the metal and further oxidation
What is the reaction used to form ammonia?
N₂+3H₂⇌2NH₃
How are elements arranged in a modern periodic table?
Groups - number of electrons on the outer shell Periods - number of outer shells
How can different conditions affect how quickly equilibrium is reached?
-Colder means particles move slower so it takes longer -Hotter means its faster
How do atom economy and yield determine choice of reaction pathway?
-Reactions can have a high yield but low atom economy because of waste products -Better to have a low yield and less waste - atom economy can be improved by using waste products
What is an experiment to determine empirical formula of a compound?
1.Weigh a crucible (with its lid). 2.Put a sample of clean magnesium ribbon into the crucible and weigh it with the lid. Calculate the mass of magnesium by subtracting the mass of the empty crucible. 3.Strongly heat the crucible over a Bunsen burner for several minutes. 4.Carefully lift the lid from time to time to allow sufficient air into the crucible for the magnesium to fully oxidise without letting any magnesium oxide escape. 5.Continue heating until the mass of the crucible reaches a constant (maximum) mass, indicating that the reaction is complete. 6.Measure the mass of the crucible and contents again. 7.Calculate the mass of the magnesium oxide by subtracting the mass of the empty crucible. 8.To work out the empirical formula, you need the mass of the magnesium (from step 2) and the mass of the oxygen atoms as well. To find the mass of the oxygen atoms, subtract the mass of magnesium used from the mass of the magnesium oxide (from step 6). Now divide each of the two masses by the relative atomic masses of the elements and simplify the ratio.
What safety precautions should you take when handling acids and alkalis?
-Wear eye protection -Tie up hair -Wash your hands immediately if you get any of it on your hands -Handle with care
What are some allotropes of carbon?
-Diamond -Fullerene -Graphite -Graphene
What do -ide endings mean?
Negative ions containing only one element (except OH⁻)
What is the relative mass and charge of an electron?
Mass = 0 Charge = -1
What does filtration look like?
How does the rusting of iron occur?
Iron rusts when it comes into contact with water or oxygen Reacts with the oxygen to form rust
What conditions are used for the Haber process?
Pressure of 200 atmosphere Temperature of 400-450⁰c Iron catalyst used to speed up reaction
How do metals at the bottom (Cu, Ag, Au) of the reactivity series react with water and acid?
water = don't acid = don't
What electrode does reduction occur at?
Cathode
What is the order of energy in the states of matter highest to lowest?
Gas, liquid, solid
Where are non-metals on the periodic table?
Right
What are factors that should be considered when choosing a reaction pathway?
-Energy consumption -Rate of reaction -Raw materials -Conditions for a high yield
What ions are present in all acidic solutions?
H⁺
What are the differences between covalent simple molecules and giant covalent structures?
-Melting and boiling point -Intermolecular forces -State at room temperature
What are some compounds with -ide endings?
-Bromide -Chloride -Oxide
How are conditions chosen for industrial reactions?
-Lowest temperature and pressure possible as it's cheaper to maintain -Compromise on yield to get speed -Raw materials must be financially viable and available
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