5. Separate Chemistry I Flashcards
(32 cards)
what properties do transition metals have that are the same as all other metals?
- shiny
- malleable
- ductile
- can conduct electricity
What are physical properties of transition metals?
- high melting points (apart from mercury)
- high density
What are chemical properties of transition metals?
- colourful compounds - depends on ions usually contained
- make good catalysts (ex IRON in Haber process)
what is corrosion?
destruction of metals by a chemical reaction with substances in the environment (oxygen)
what’s rusting?
corrosion that only happens when iron or steel react with water & oxygen only
iron + oxygen -> hydrated iron (II) ocifr
- flakes off which exposes the metal to even more air which creates further rusting
What are barrier methods of rusting
- coat with a barrier to keep water, oxygen¨
- paint with coating plastic
- oiling 7 greasing used on moving parts as even when in not direct direct contact the oil repels water present in oxygen
- store metal in unreactive metal
- desicant powder absorbs water vapour which keeps water vapour away
How does galvanising prevent the iron from rusting?
Zinc is coated on iron to prevent it from corroding as it is more reactive.
if coating is damaged, iron is still protected as the zinc will continue to corrode and it loses electrons easily so iron accepts these electrons thus it doesn’t undergo oxidation.
What’s sacrificial protection?
magnesium or zinc attaches to iron blocks to intentionally be corroded so i
What is electroplating?
coating the surface of a metal with a thin layer of another metal using electrolysis
State two reasons why metals should be electroplated.
it increases the ability to exclude water and oxygen which increases the ability to resist corrosion
- it improves appearances - gold/silver can be plated with onto cheaper base metals for jewelry as they are unreactive and will not corrode
What are the stages of electroplating?
the metal to be plated as a cathode and metal you’re plating with is used as an anode and there’s an electrolyte containing ions of the metal being used to the plating.
- at cathode, ions in electrolyte move to cathode which gains them
- at anode, ions in electrolyte metal loses electrons and becomes ion which goes into electrolyte
- longer the current thicker the plating metal on mtal becomes
how does tin plating
inner surfaces of steel are coated with tin which doesn’t react with water and oxygen at room temperature so it stops contact with steel
- however if damaged, the steel will corrode as it is more reactive than tin
what is an alloy?
mixture of metals with one or more elements
How does converting pure metal into alloys increase the strength of the product?
- pure metals are malleable as they are in regular arrangemenet of identical atoms so layers of ions slide over each other this mean they’re NOT STRONG!
- alloys have different sized ions which disrupt the layers of ions thus they can’t slide - STRONG
why is iron alloyed with other metals to produce different alloy steels?
low carbon steels are malleable - used for sheeting
high carbons steels are hard - used for cutting tools
stainless steel resistant for corrosion - used for cutlery
what are uses of alloys in everyday life?
aluminium : low density - aircraft
( pure aluminium is not strong enough for aeroplanes)
copper : good conductor - electrical cables
magnalium : low density - used in cars and aeroplanes
brass : hard and corrosion resistant - coins, medals,
actual yield
mass of substance produced when you carry out an experiments
theoretical yield
mass of substance thats calculated or obtained by theory
what is the equation for percentage yield
percentage yield = a
why is it important to use reactions with the highest yield?
higher yield means more useful the reaction is which means fewer materials make the same amount of product which means less profit and more profit
why do you not never get 100% of yield
- incomplete reaction - not all reactants are converted to product / not left for long enough
- product is lost - lose some when transferring liquids between containers
- unwanted reaction - reactions may react with different products or impurities on reactants
what’s atom economy
measure of amount of reactants that end up as useful products
- important for sustainable developmet and economic reasons to use reactions with high atom economy
atom economy
why should a particular pathway be chosen
high atom economy - more profitable and low use expensive raw materials and waste that’s expensive to remove
percentage yield
high rate of reaction - produe amount of product needed in a sensible amount of time
if reaction is reversible keep yield high u need to alter the equilbrium position by changing reaction conditions
look at byproducts
