C4 Chemical changes Flashcards
acid + metal?
salt + hydrogen gas
metal oxide + acid?
salt + water
metal carbonate + acid?
salt + carbon dioxide + water
metal hydroxide + acid?
salt + water
alkali + acid?
salt + water
what is the formula for sulphuric acid?
h2so4
what colour does a weak acid in UI turn?
orange
why is UI good for distinguishing between strong/ weak acids/ alkalis?
it is a mixtures of different indicators (dyes)
why are most indicators different from UI?
most indicators have 1 colour change and that is mostly at neutral
describe a method to make pure, dry crystals of calcium nitrate from a metal oxide and a dilute acid [RP - making salts]
-use calcium oxide and nitric acid
-warm nitric acid up
-add calcium oxide until its in excess (it stops reacting)
-filter solution to get pure calcium nitrate and water
-heat this until to start to get crystals as you evaporate the water
-pat the crystals dry with a paper towel
in the RP of making copper sulphate crystals, why is the sulphuric acid heated before adding copper oxide?
it won’t react as much as with the acid
in the RP of making copper sulphate crystals, why is copper oxide is added until it is in excess?
it makes sure that all the acid is reacted
in the RP of making copper sulphate crystals, why is excess copper oxide used rather than excess sulphuric acid?
zinc oxide can be filtered out
in the RP of making copper sulphate crystals, give one observation that the student could make to show that the zinc oxide is in excess
the solid zinc oxide can be seen collecting at the bottom
in the RP of making copper sulphate crystals, why is copper sulphate heated in an evaporating basin?
it has a large surface area so the water evaporates quicker, it spreads the heat out more evenly
in the RP of making copper sulphate crystals, why do we leave them to dry instead of heating it?
the slower they cool, the bigger the crystals
define concentration
measure how much particles you have per unit of volume
in both concentrated and dilute acids what strengths do they have?
the both have the same strength
what element do all acids have?
hydrogen
what do strong acids/alkali do in water?
they fully ionises in water (fully split up into its ions)
what do weak acids/ alkali do in water?
they partially ionise in water
what is the pH scale?
it is a measure of the concentration of hydrogen ions in a solution
which other scale is the pH scale similar to?
the pOH scale
what is the pOH scale?
for every decrease in pH by 1 the hydrogen ion concentration increases by a factor of 10
define ore
a naturally occurring rock that contains enough metals or metal compound to make it (profitable) economically viable to extract
what is oxidation?
the gain of oxygen
what is reduction?
the loss of oxygen
what is a redox reaction?
where the oxidation and reduction occurs at the same time
what type of reaction is this and why:
lead oxide+ carbon -> carbon dioxide + lead
a displacement reaction, the carbon displaces the metal oxide to form carbon dioxide
what type of oxygen based reaction is this and why:
lead oxide+ carbon -> carbon dioxide + lead
reduction reaction, the lead oxide loses its oxygen
why is this a redox reaction:
lead oxide+ carbon -> carbon dioxide + lead
the lead loses oxygen and the carbon gains it
generally, how can we get metals from their ores and why?
by reduction with carbon, as it is less reactive than carbon
how to we get a metal from a metal carbonate?
-heat metal carbonate
-this gives carbon dioxide
-left with metal oxide
-heat this with carbon
-this gives carbon dioxide
-left with metal
how do we get a metal from a metal sulphide?
-heat metal sulphide in air
-this gives sulphur dioxide
-left with metal oxide
-heat this with carbon
-this gives carbon dioxide
-left with metal
how would you get lead from lead sulphide (oxidation)?
-heat lead sulphide in air which gives lead oxide and sulphur dioxide
[lead sulphide + oxygen -> lead oxide + sulphur dioxide]
-lead oxide is heated with carbon to give lead and carbon dioxide
[lead oxide + carbon -> lead +carbon dioxide]
how would you get copper from copper carbonate (decomposition)?
-heat the copper carbonate on its own to give copper oxide and the gas carbon dioxide
[copper carbonate -> copper oxide + carbon dioxide]
-the copper oxide is heated with carbon to give copper and carbon dioxide
[copper oxide + carbon -> copper + carbon dioxide]
what state symbol would you use for any liquid that isn’t water?
aqueous (aq), typically all acids and alkali would be aqueous
what is oxidation?
loss of electrons
what is reduction?
gain of electrons
if magnesium went form Mg0 to Mg2+ what happened to magnesium?
it became oxidised, it lost electrons as it became positive
if copper went form Cu3+ to Cu0 what happened to copper?
it became reduced, it gained electrons and became neutral
what do half equations show?
which elements are oxidised and which one is reduced
A formulation is a __________ that has been designed as a useful product. Which word completes the sentence?
mixture
True or false? A pure substance has a sharp melting and boiling point.
true
True or false? Impurities in a chemical lead to changes in the melting and boiling point of the chemical.
true; If a solid contains impurities, it will melt at a lower temperature and over a range of temperatures.
True or false? Pure substances always consist of single elements only.
false; Pure substances can be single elements or a single compound.
Cleaning agents are complex mixtures of chemical components, each with its own specific purpose. The components have very precise measurements to ensure that the cleaning agent has the right properties. What is a cleaning agent an example of? (Hint: it’s a type of mixture).
formulation
True or false? A compound can have different Rf values in different solvents.
true; Substances have different solubilities in different solvents, so they will be carried different distances during chromatography.
What is the missing word? In paper chromatography, the solvent used is known as the __________ phase.
mobile
When an acid reacts with a base a salt is produced along with another product. Name this product.
water
what are the products when acid + base?
acid + base → salt + water
What name is given to substances (both soluble and insoluble) such as metal hydroxides and metal oxides that can neutralise acids?
Bases neutralise acids.
True or false? Only metals above hydrogen in the reactivity series react with acids to make a salt and hydrogen.
true; Metals below hydrogen in the reactivity series cannot displace the hydrogen from the acid.
what are the key stages of producing any dry crystals?
-heat acid
-add oxide until excess and filter
-heat salt solution to crystallizing point
-leave to fully evaporate and pat dry
what happens as pH decreases by one unit?
the hydrogen ion concentration of the solution increases by a factor of 10
is strong/ weak the same as concentrated/dilute?
no; strong and weak refers to the amount of substance in a given volume
what is the half equation for the production of sodium?
Na+ + e- –> Na
what type of particle passes through the mesh in the electrolysis of molten sodium chloride?
ion
what is the alkaline solution produced when aqueous sodium chloride solution is electrolysed?
sodium hydroxide
what does the reactivity of metal depend upon?
its ability to lose electrons and form a positive ion
which metals react with water (most to least)?
potassium, sodium, lithium, calcium
which metals react with dilute acid (most to least)?
potassium, sodium, lithium, calcium, magnesium, carbon, zinc, iron
what does titration do?
The volumes of acid and alkali solutions that react with each other
can be measured by titration using a suitable indicator.
