C5 chemistry OCR Gateway

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  • Created by: charlotte
  • Created on: 11-06-13 18:52
equation to find the number of moles
mass in g of element or compound / relative formula mass of element or compound
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equation for the percentage composition by mass
( relative atomic mass x no. of atoms of that element / relative formula mass of whole compound ) x100
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equation for concentration
no. of moles / volume
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what is electrolysis?
splitting up with electricity
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method of electrolysis
an electric current is passed through a molten or dissolved ionic compound causing it to decompose. 2 electrodes: positive: anode (electrons taken away from) & negative: cathode. (electrons given to)
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the amount of product made during electrolysis can be increased by:
increasing time & current
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conversion from cm3 to dm3
1000cm3 = 1dm3
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why is concentration important?
food preparation, medicine (too dilute, they wont work), weedkiller (not dilute enough, plants will die)
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what is titration?
a method of analysing the concentrations of solutions, they are very accurate and allow you to find out the exact quantity of acid needed to neutralize it
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what is a universal indicator used for
estimating the pH of a substance, each colour represents a narrow range of pH values
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advantages and disadvantages of using an upturned cylinder
adv: gives data to nearest cm3, accurate. dis: things like H, Cl & NH3 will dissolve in the water
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adv & dis of using gas syringe
adv: very accurate, data to nearest cm3. dis: if reaction is too vigorous it can blow out the plunger
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adv & dis of using mass balance
adv: extremely accurate. dis: it releases gases into the room
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facts about reactions
1. amount of gas produced is directly proportional to amount of limiting reactant. 2. reactions stop when one of the reactants is used up (the limiting reactant) 3/ if you halve the amount of the limiting reactant. the amount of gas will also halve
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what is a reversible reaction
where the products of the reaction can themselves react to produce the original reactants
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what is equilibrium
at equilibrium the concentrations of the reactants and products are constant but not necessarilly equal
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factors that affect the position of the equilibrium
temperature (decreased temp = increased eq.), pressure (increased pressure = decreased eq.), concentration (increased conc. = decreased eq.)
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what is the contact process
a method of producing sulfuric acid at the high concentrations needed for industrial processes
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stages of the contact process
1. make sulfur dioxide by burning sulfur in air 2. sulfur dioxide is oxidised to make sulfur trioxide. 3.water is added to sulfur trixiode to make water
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strong acids..
ionise completely in water, almost all of the H+ ions are released
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weak acids..
partially ionise in water, only some H+ ions are released
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uses of weak acids
descaler (for kettles etc.)
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precipitation is
a reaction involving 2 solutions which makes an insoluble substance (the precipitate)
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Other cards in this set

Card 2


equation for the percentage composition by mass


( relative atomic mass x no. of atoms of that element / relative formula mass of whole compound ) x100

Card 3


equation for concentration


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Card 4


what is electrolysis?


Preview of the front of card 4

Card 5


method of electrolysis


Preview of the front of card 5
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