Chemistry: Patterns of behaviour 8abcdefgand h Flashcards
How can we test to see if a small amount of gas is hydrogen?
Insert a lit splint and hydrogen will give a sqeaky pop!
Rust is the name given to which metal oxide?
Iron oxide
What is iron reacting with when it rusts?
Oxygen, water also become loosely bonded to form hydrated iron oxide.
Why does rust get worse and worse?
It is crumbly and so falls off to expose more iron, which then rusts.
What two condidtions can increase the speed at which iron rusts?
Salty and acidic conditions.
Cars made from aluminium do not corrode, why is this?
Aluminium oxide, which forms of the surface, is a hard, protective layer, very unlike rust.
If aluminium doesn’t rust why aren’t more cars made from it?
It is much more expensive than steel.
Metal + acid —>
salt + hydrogen
metal + oxygen —->
metal oxide
What happens in a displacement reaction?
A more reactive element pushes a less reactive one out of a compound.
Give an example of a displacement reaction involving zinc and copper sulfate.
Zinc + copper sulfate —->Zinc sulfate + copper
Which metal is more reactive, potassium or magnesium?
potassium
Why is lead suitable for roofing, whereas sodium would not be?
Sodium very reactive, would react with rain whereas lead is much less reactive and easily mouldable.
Why does the reactivity of gold and silver make it so useful for jewellery making?
They do not corrode easily and so stay shiny. They also don’t react with moisture on our skin so irritation to skin is less likely.
Most reactive metals are not found naturally. Chemical reactions are necessary to obtain them, why is this?
They exist as compounds within rocks, only the least reactive metals, like gold, are found naturally.
Gold and silver are often used for electrical contacts, why is this?
They are so unreactive that they are safer with electricity passing through them.
If I tested a weak acid with univeral indicatior what colour would I expect to see? What pH is it likely to be?
Yellow/Orange. pH6 to 4.
If I tested a strong alkali with universal indicator, what colour would I expect to see and what pH would I expect?
Dark blue/ purple. Ph 13/14
Other than universal indicator, what indicator have you seen?
Litmus paper
What colours does litmus paper come in?
Pink (tests for alkalis) blue (tests for acids) and purple (tests for both aicds and alkalis)
What would happen it I put a drop of acid onto: a) pink litmus paper? b) blue litmus paper
a) stay pink b) goes pink
If I put a neutral solution, such as tap water, on to universal indicator what colours would I expect to see? What pH would I expect?
Green, pH 7.
What is the best thing to use to help remember the colours of univeral indicator.
The colours of a rainbow…with strong acid at the red end and strong alkali and the purple end.
When a metal (e.g. Iron) is added to an acid (hydrochloric acid) a salt is formed….how is the name of the salt found?
First part of the name comes from metal, second part from acid. In example it would be Iron Chloride.
What salt is formed when zinc reacts with sulfuric acid?
Zinc Sulfate (plus hydrogen)
What are the three types of neutralisation reactiond and their products?
Metal + acid —> salt + hydrogen Metal Oxide + acid–> salt + water Metal carbonate + acid —> salt + water + carbon dioxide
When are neutralistion reactions helpful?
When we have excess acid (indigestion) in our stomachs we can take powder to neutralise it, when we need to neutralise acidic soil and when we make fertilizer.
What is formed when non metals react with oxygen?
Acidic compounds e.g. carbon dioxide or sulphur dioxide (both of which make acids when dissolved).
What is formed when a metal reacts with oxygen?
A base, which forms an alkali if it dissolves.
What is the chemical name for limestone?
Calcium carbonate
What happens to limestone when it is heated?
It thermally decomposes to form calcium oxide, carbon dioxide is released in this reaction.
What is formed when limstone is put in dilute hydrochloric acid?
Calcium chloride solution, water is formed and carbon dioxide is released.
Why is crushed limestone sometimes put on fields?
To neutralise acidic soil.
What is thermal decomposition?
When a compound is broken down as result of heat alone.
What is oxidation?
The gaining of oxygen or a loss of electrons.
What is reduction?
Losing oxygen or gaining electrons.
What is formed in complete combustion of hydrocarbon fuels, e.g. methane (when there is plenty of oxygen available) ?
Carbon dioxide and water.
What is formed in incomplete combustion of hydrocarbon fuels (e.g. methane)?
Soot (carbon) or carbon monoxide and water.
What colour flame do we see when there is incomplete combustion?
Yellow or orange.
What colour is the flame seen when complete combustion is happening?
Blue
What colour are potassium manganate VII crystals?
Dark purple, they dissolve to make a purple solution.
Copper carbonate is a green powder, what happens when it is heated?
It turns black as it becomes copper oxide, carbon dioxide is released.
