GCSE Chemistry C2 Edexcel

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Describe the nucleus in the atom?
It's in the middloe of the atom, it contains protons and neutrons, has an overall positive charge (because of protons), accounts for nearly all of the atoms mass, tiny compared to the atom as a whole
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Describe the electrons in the atom?
They move around the nucleus, have a negative charge, tiny compared to nucleus but move around and cover alot of space, the size of their orbits determines how big the atom is, virtually no mass and occupy shells around the nucleus
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What's a shell?
An energy level around the nucleus
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How does the number of protons compare to the number of electrons?
They are the same
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What charge do protons, neutrons and electrons have?
+1, 0 and -1
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How does the number of neutrons relate to the number of protons/electrons?
It isn't fixed, but usually around the same number
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What is the mass of protons, neutrons and electrons?
1,1 and 1/2000
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What are the 5 electron shell rules?
Electrons always occupy shells, the shells closest to the nucleus are filled first, only 2 electrons in the first shell then 8 per shell, atoms are happier with a full outer shell, in most atoms the outer shell isn't full so they want to react
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What part of the atom determines what element it is?
The number of protons
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What's the atomic number?
How many protons/electrons in an atom
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Which elements share atomic numbers?
None, each element has its own unique atomic number
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What's the mass number?
The total number of protons and neutrons in the atom
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Why doesn't mass number account for electrons?
They have a negligible mass
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How do find the number of neutrons?
Mass number-atomic number
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What are isotopes?
Isotopes are different forms of the same element which have the same number of protons but a different number of neutrons
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What's relative atomic mass?
The average mass of the isotopes of an element
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What's relative abundance?
How much there is of an isotope compared to the total amount of the element in the world
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How do you calculate relative atomic mass?
(mass 1 x abundance 1)+(mass 2 x abundance 2)/(abundance 1+ abundance 2)
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Who arranged the elements in groups?
Dmitri Mendeleev
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When did Mendeleev first arrange elements in to groups?
1869
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How did Mendeleev arrange elements into groups?
Grouped them according to their properties in vertical groups
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Why were the gaps in Mendeleev's table clever?
They predicted the properties of undiscovered elements
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3 examples of elements found that fit Mendeleev's gaps?
Scandium, gallium and germanium
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Where are metals and non metals on the periodic table?
On opposite sides
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What are the rows in the periodic table called?
Periods
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Describe how periods relate to the periodic table?
The elements are arranged in order of increasing atomic number along each period, the period number is the same as the number of shells (period 3=3 shells), element properties change along a period
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What are the vertical columns in the periodic table called?
Groups
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Describe how groups relate to the periodic table?
Elements in the same group have similar properties, group number is equal to number of electrons in the outer shell (group 2=2 electrons on outer shell, element properties change gradually down a group
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What is ionic bonding?
Transfer of electrons to form charged atoms called ions
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What are charged atoms called?
Cations (positive) and anions (negative)
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Why are ionic bonds strong?
The attraction of opposite charges
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What do metals do in ionic bonding?
Give away one or two electrons to have a full outer shell, they become cations after this
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What do non metals do in ionic bonding?
Gain one or two electrons to have a full outer shell, they become anions after this
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Which 4 groups are most likely to form ions?
1,2,6 and 7
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What are ionic bonds always between?
A metal and a non metal
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What happens when cations join with anions?
They form ionic bonds
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Describe the structure of ionic compounds?
Regular lattice structure, ions form a closely packed regular lattice arrangement
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Why do ionic compounds have a lattice structure?
Ionic bonds are very strong electrostatic forces of attraction between oppositely charged ions
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What are 2 properties of ionic compounds?
High melting/boiling point, conduct electricity when aqueous or molten
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What's the reason for ionic compounds having the 2 named properties?
Very strong bonds between the ions means lots of energy is required to break the bonds, when aqueous the ions separate and are free to move and carry electric current, the same happens when they melt
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What's the rule for naming compounds when 2 different elements combine?
The name ends in 'ide'
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What's the rule for naming compounds when 3+ elements combine and one is oxygen?
The name ends in 'ate'
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How do you work out a compound's formula?
Look at the charges of the ions involved and make the charge neutral
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What are the rules of solubility for common salts of sodium, potassium and ammonium?
Always soluble
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What are the rules of solubility for nitrates?
Always soluble
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What are the rules of solubility for common chlorides?
Soluble except silver chloride and lead chloride
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What are the rules of solubility for common sulfates?
Soluble except lead sulfate, barium sulfate and calcium sulfate
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What are the rules of solubility for common carbonates and hydroxides?
Insoluble except for sodium, potassium and ammonium ones
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Describe the practical to make insoluble salts?
Pick the right 2 soluble salts, mix solutions in a beaker, filter out precipitate, wash with distilled water, dry
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An example of an insoluble salt?
Barium sulfate
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How do you choose the right 2 salts?
They must be soluble, one's name beginning must be same as desired product, one's name end must be same as desired product
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How is barium sulfate used?
X rays, shows up the gut, called a barium meal
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What colour flame would sodium produce during a flame test?
Yellow/orange
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What colour flame would calcium produce during a flame test?
Red
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What colour flame would copper produce during a flame test?
Blue/green
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Do flame tests work with compounds?
Yes
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How do you perform a flame test?
Dip clean wire loop in compound and observe colour, with solids dip in hydrochloric acid to moisten so it sticks
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What's a flame test used for?
To test for calcium, potassium, sulfate and copper ions
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How do you test for carbonates?
Bubble gas through lime water, lime water turns milky if carbon dioxide is present, also can test solids because reacts with acid to form co2, acid+carbonate into salt+water+carbon dioxide
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How do you test for sulfate ions?
Add dilute hydrochloric acid to barium chloride solution, a white precipitate of barium sulfate means original compound was a sulfate
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How do you test for chloride ions?
Add dilute nitric acid to silver nitrate solution, a chloride gives a white precipitate of silver chloride
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What is spectroscopy?
Similar to flame test, sample heated, light patterns looked at, each element produces different patterns
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Describe spectroscopy?
Fast and reliable, can detect small amounts of an element, led to discovery of rubidium and caesium because they produced unseen patterns
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What's covalent bonding?
Sharing pairs of electrons between atoms
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What's it called when atoms make covalent bonds with others?
A molecule
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What are the 2 kinds of covalent substance?
Simple molecular and giant molecular
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Describe simple molecular covalent substances?
Atoms make strong covalent bonds to form molecules, forces of attraction between molecules is weak, low melting/boiling point because of weak molecular attraction, , most are gas/liquid at room temperature, don't conduct electricity (no ions)
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Describe giant molecular covalent substances?
Similar to ionic lattices but without charged ions, atoms bonded by strong covalent bonds, high melting/boiling points, never conduct electricity (except graphite), insoluble in water
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2 examples of giant molecular covalent substances?
Diamond and graphite, both made from carbon
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What is the hardest natural substance?
Diamond
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How is diamond formed?
Carbon atoms form 4 covalent bonds in a very rigid giant covalent structure, doesn't conduct electricity because there are no free electrons
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Describe graphites ability to conduct electricity?
Each carbon atom only forms 3 covalent bonds which creates sheets of carbon atoms which can slide over each other (lubricant), layers held very loosely together, lots of spare electrons which can move so can conduct electricity
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What does immiscible mean?
2 liquids cannot mix
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How would you separate immiscible liquids?
2 liquids shaken then form layers, separating funnel, open tap to drain denser layer
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How would you separate miscible liquids?
Liquids must have different boiling points, liquids condense at different temperatures for separate collection, fractional distillation
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Describe how liquid air is fractionally distilled?
Filtered to remove dust, cooled to -200 to become miscible liquid mixture, during cooling water vapour condenses and is removed, carbon dioxide freezes and is removed, liquid heated slowly, gases move up then condense at different levels
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What 2 gases come out together during fractional distillation of air?
Oxygen and argon
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What's chromatography used for?
To identify substances
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Describe paper chromatography?
Used to identify substances in a mixture, based on the fact that different substances go through water at different rates
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Describe THE METHOD of paper chromatography?
Put spots of each mixture on a pencil baseline on filter paper, roll up paper then put in a beaker containing a solvent (eg water/ethanol), solvent moves up paper and moves samples, different chemicals form different spots, produce chromatogra
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What's an RF value?
Ratio of distance travelled by substance compared to solvent
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How do you calculate RF value?
Distance travelled by substance/distance travelled by solvent
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Which industries are RF values used in?
Food and forensic science
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Where are the metals on the periodic table?
Left and middle
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What are 2 properties of most metals?
Conduct electricity well (eg used in wires), malleable meaning they can be bent or hammered into shapes (eg car bodies)
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What are the 2 additional properties of transition metals?
High melting points, form very colourful compounds (eg used in hair dyes)
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What 'gives' metals their properties?
Their structure, layers of electrons can slide
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Describe the structure of metals?
Regular arrangement of atoms held together with metallic bonds, metallic bonds give metals a giant structure consisting of positive ions and free electrons because metallic bonds let outer electrons move freely, creates 'sea' of free electrons
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What are the elements in group 1 called?
Alkali metals
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How are alkali metals different from other metals?
Soft (can be cut with a knife), low melting points
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What's a property of alkali metals?
They react vigorously in water to form hydroxides and make an alkaline solution (hence the name)
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What's the trend of reactivity with alkali metals?
Further down the group they're more reactive because electrons are further form nucleus so weaker attraction so easier to get rid of, elements in group 1 get more reactive as atomic number increases
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What do group 1 reactions with water produce?
Hydrogen gas which fizzes and can be identified by placing a lighted splint over the reaction and hearing a squeaky pop
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What are the elements in group 7 called?
Halogens
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What's true of all halogens?
They all have 7 electrons in their outer shell
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Describe the reaction between halogens and metals?
Halogens react with metals to form salts called metal halides
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Describe the reaction between halogens and hydrogen?
Halogens can react with hydrogen to form hydrogen halides
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Describe hydrogen halides?
Soluble in water, when dissolved in water they form acidic solutions
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What's the trend of reactivity with halogens?
Higher up group 7 means more reactive because outer shell closer to nucleus so pull for other electrons is stronger, when halides dissolve in water the halide ions are free to react, more reactive halogen will displace others in halide solution
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What are the elements in group 0/8 called?
Noble gases
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Describe noble gases at room temperature?
Colourless gases
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What do noble gases react with?
Noble gases are inert because they have a full outer shell, they're also non flammable and hard to observe
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How were noble gases discovered?
Chemists noticed that nitrogen from the air had a different density to nitrogen taken from chemical reactions therefore other gases must be mixed in, discovered using fractional distillation of air
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Uses of argon?
Argon provides an inert atmosphere in filament lamps, prevents filament from burning, protects metals from burning when melding
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Uses of helium?
Airships and party balloons, has lower density than air so floats
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What's the trend of with noble gases?
Higher densities and boiling points as you move down the group
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What must happen to break bonds?
Energy must be supplied
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What's the process of bond breaking?
Endothermic reaction
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What's the process of bond making?
Exothermic reaction
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What's an exothermic reaction?
Gives out energy in the form of heat to the surroundings
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Why do exothermic reactions cause a rise in temperature?
The energy released in forming bonds is greater than the energy used in breaking old bonds in the reactants
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An example of an exothermic reaction?
Burning fuels, making new bonds of water with carbon dioxide gives out more energy than breaking bonds in the fuel
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What's an endothermic reaction?
Takes in heat energy from surroundings
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Why do endothermic reactions consume heat?
The energy required to break old bonds in the reactants is greater than the heat energy released by forming new bonds
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Which of the 2 reactions is more common?
Exothermic
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2 examples of endothermic reactions?
Photosynthesis, ammonium nitrate dissolving in water
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Which reaction has happened if the products are at a lower energy than the reactants?
Exothermic
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Which reaction has happened if the products are at a higher energy than the reactants?
Encodthermic
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Which 4 reaction types would you need to measure the temperature for?
Dissolving salts in water, neutralization (acid+base), displacement, precipitation
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How do you measure the energy produced by a chemical reaction?
Take temperature of reactants, mix in polystyrene cup then measure at end of reaction
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How do you combat heat loss in temperature measurements?
Put cotton wool around the cup
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What's one of the slowest reactions?
The rusting of iron
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What 4 things does the rate of reaction depend on?
Temperature, concentration (pressure for gases), catalyst, surface area of a solid (or size of particles)
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How do you tell which reaction is quicker on a graph?
The line that goes flat the quickest
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Describe the practical to investigate effect of surface area and concentration on reaction rate?
Hydrochloric acid+marble chips, measure gas produced by a gas syringe, repeat with same variables but crush chips more, repeat with powdered chips
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Describe the practical to investigate affect of temperature on reaction rate?
Sodium thiosulfate and HCL, react to form yellow sulfur precipitate, look at black paper through solution, reaction ends when mark not visible, repeat at different temperatures
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How do catalysts affect rate of reaction?
Catalysts lower the energy required by the reactants to react, makes it easier for reaction to happen and increases reaction rate, allows lower temperature to be used
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Use of catalysts?
Catalytic converters in vehicle exhausts, speeds up carbon monoxide into carbon dioxide+water reaction
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What's the generic reason that reaction rate increases?
Increased collisions
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Why does higher temperature increase reaction rate?
The particles have more energy and move quicker so there are more frequent collisions
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Why does higher concentration (or pressure) increase reaction rate?
More particles of reactant leading to more likely collisions, in a gas the particles are squashed more closely so more frequent collisions
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Why does larger surface area increase reaction rate?
Particles have a larger area to react with so more frequent collisions
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How do catalysts increase reaction rate in terms of collisions?
Gives reacting particles a surface to stick to leading to increased successful collisions by lowering required energy
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What do reactions need in order to happen?
Enough energy to collide with
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How do you find the relative atomic mass (RAM)?
Look at the mass number (it's the same)
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What is relative formula mass (RFM)?
All of the RAM's added together in a compound
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How do you work out RFM?
Add all RAM's together, including the quantities of each element (eg cl2 requires RAM x2)
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How do you calculate percent mass of an element in a compound?
RAM x number of atoms (of element)/ RFM (of whole compound) x 100
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What is the empirical formula?
The exact formula of a compound worked out bu finding ratios of elements to each othet
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How do you calculate empirical formula from masses?
List all elements in the compound, write given masses for the experiment, divide mass by RAM (individually), divide answer by lowest answer of all elements
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How do you calculate masses in reactions?
Write out the balanced equation, work out RFM (for the 2 bits you want), divide one RFM by itself to get 1 then multiply to work out any mass, do the same to both sides
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What is percentage yield?
A comparison of actual and theoretical yield
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What's reaction yield?
The mass of a product it produces
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How do you calculate percentage yield?
actual yield/theoretical yield then x 100(all units in grams)
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How often do you get a 100% yield
Almost never
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What are 3 reasons for less than 100% yield?
Incomplete reactions (not all reactants converted to product), practical losses during experiment (eg transferring liquid between containers), unwanted reactions (other reactions using up reactants)
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What do chemists look for in reactions for an industry?
High percentage yield so no expensive raw materials are wasted, all products are commercially useful, suitable speed (quickly and safely)
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Card 2

Front

Describe the electrons in the atom?

Back

They move around the nucleus, have a negative charge, tiny compared to nucleus but move around and cover alot of space, the size of their orbits determines how big the atom is, virtually no mass and occupy shells around the nucleus

Card 3

Front

What's a shell?

Back

Preview of the front of card 3

Card 4

Front

How does the number of protons compare to the number of electrons?

Back

Preview of the front of card 4

Card 5

Front

What charge do protons, neutrons and electrons have?

Back

Preview of the front of card 5
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