Chemistry Flashcards
Name the test procedure and observation or result and reason for observation for the laboratory test for hydrogen
Test -of burning wooden splint
Procedure – hold a burning splint at the open end of a test tube of gas.
Observationi-it burns with a loud squeaky pop
Reason for observation – it is as a result of the rapid combustion of hydrogen with oxygen to produce water.
How does rust occur or define the term rust
Rust occurs when water vapour from a condenses on iron or steel and forms a film on the surface of the metal.
oxygen dissolved in the water and reacts with this metal to form iron. The chemical name for rust is iron oxide
What is the chemical name for rust and what colour is rust
The chemical name for rust is iron oxide and rust is brown in colour.
Rust can be prevented by keeping oxygen and moisture away from iron or steel through the following ways
Painting surface is made of iron or steel.
Boiling or covering iron with oil
chromium plating for steel covering the surface with chromium which corrosion resistance.
Galvanizing which is covering the iron with a layer of zinc zinc is more reactive than iron and therefore it corrodes instead of the iron
sacrificial protection which is a process where a more reactive than iron is put the reactive metal reacts with oxygen instead of iron in this case iron is protected at the expense of the more reactive metal and for this reason it is called sacrificial protection
What is the reactivity series
The reactivity series of metals but how readily they react starting with the most reactive
Tell me the reactivity series in order from most reactive to least reactive
Potassium
sodium
calcium
magnesium
aluminium
carbon
zinc
iron
Tin
lead
Hydrogen
copper
silver
gold
Platinum
Something to remember these is
please stop calling me a careless zebra instead try learning how copper saves gold poo
What is a displacement reaction
A displacement reaction is a reaction when a more reactive elements displaces less reactive element from a compound that contains the less reactive element. Or a reaction in which a more reactive elements displaces less reactive element from its solution.
Displacement reactions alternative name
Displacement reactions are also called replacement reactions.
General observations during a displacement reaction
The more reactive metal gradually disappears as it forms a solution.
The less reactive metal is deposited at the bottom of the solution
Example – when a piece of magnesium is dipped into blue copper sulphate solution; the following observations are made:
The blue colour fades as colorless magnesium sulphate solution forms and the brown copper is deposited at the bottom of the solution
So the equation for this reaction is magnesium plus copper sulphate equals magnesium sulphate + copper
Note that no observable change is seen if you put copper powder into magnesium sulfate solution and this is because Papa is not receive enough to displace magnesium from magnesium sulphate solution.
Chemical reactions and energy
When a chemical reaction takes place energy may be given out or taken in.
Examples of reactions that give out energy and examples of reactions that take in energy
Reactions that give out energy are
Burning of gas in a Bunsen burner
reactions of metals and acids
reactions of metal carbonate and acid
neutralization reactions
Explosion of petrol vapour in a car engine
examples of reactions that take in energy are
photosynthesis
the decomposition of limestone to make lime
Which metals can be extracted using carbon and which metals cannot be extracted using carbon
Metals which can be extracted using carbon only lower reactive than carbon-these metals are zinc iron tin Lead and copper
Metals which cannot be extracted using carbon have higher reactivity than carbon-these are are aluminium magnesium calcium sodium and potassium
Why is carbon used in the extraction of metals
Carbon is a non-metal but it’s more reactive than some metals therefore it can take away the oxygen form metal oxides first of less reactive metals than carbon can be extracted from their oxides by heating with carbon in general.
metal oxide + carbon =metal + carbon dioxide
Explain extracting copper from copper oxide with the procedure and equation
Mix copper oxide powder with carbon powder. Then hit the mixture strongly for a few minutes in a crucible. It is important to keep a lid on the crucible otherwise the carbon will react with oxygen in the air rather than with the copper oxide.
The carbon dioxide formed in the reaction escapes into the air. Let the crucible cool down did the mixture into cold water pieces of brown copper sink to the bottom living all reacted powder suspended in the water.
The equation is - copper oxide + carbon=copper + carbon dioxide
Uses of copper
Copper is used to make water pipes. This is because it does not react with cold or hot water. It is used to make basis of some kitchen pants. This is because it is a good conductor of heat. It is used for making electrical coils. This is because it is a good conductor of electricity corrodes very slowly and it is soft and therefore can be pulled into a wire. Copper is alloyed with tin to make bronze. Bronze is a highly sonorous metal and is used to make bells because of the clear ringing sound it produces.
It is alloyed with zinc to make brass. Brass is a strong and corrosion-resistant and it is used to make the pins of electrical plugs for stop brass is also a shiny metal which is used to make ornaments.
