C5 - Chemical Changes Flashcards
What happens when metals react with other substances
The metal atoms form positive ions
What is the reactivity of a metal related to
To its tendency to form positive ions
How can the metals be ordered by their reactions with water and dilute acid
They can be ordered in the reactivity series.
What non-metals are often included in the reactivity series
Hydrogen and carbon
What can happen when a more reactive metal reacts with a less reactive metal
more reactive metal can displace a less reactive metal from a compound.
Order the reactivity series (which you are required to know)
potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper
What metals in the reactivity series react with water (fizz with cold water)
potassium, sodium, lithium, calcium, magnesium, (magnesium and higher)
What metals in the reactivity series react with a dilute acid
potassium, sodium, lithium, calcium, magnesium, zinc, iron (above but not including copper)
What gas is given off if metals react with water or dilute acids
Hyrdogen gas
How are unreactive metals found (e.g gold)
In the earth as the metal itself
How are more reactive (most) metals found
as compounds that require chemical reactions to extract the metal.
How can Metals less reactive than carbon be extracted
Extracted from their oxides by reduction with carbon.
What is oxidation
The loss of electrons
What is reduction
Gain of electrons
In this ionic equation which element has been oxidised and which reduced
Fe(s)+Cu^2+(aq) -> Fe^2(aq)+Cu(s)
Iron oxidised
Copper reduced
What does the reaction between metal and an acid produce aswell as salt
Hydrogen gas
What is a redox reaction
A reaction with involves oxidisation and reduction
What is a salt
A compound formed when the hydrogen in an acid is wholly or partially replaced by metal or ammonium ions.
How can salts be made
Reacting a suitable metal with an acid. The metal must be above hydrogen in the reactivity series, but not dangerously reactive
What do all acid have
Hydrogen
What determins the salt you make
The metal you use, as well as the acid
What does the acid provide
The negative ions present in all salts
e.g sulfuric acid H^2SO^4 makes sulfates
What is the reaction between a metal and an acid an example of
A redox reaction
What is oxidised and what is reduced in a reaction between a metal and an acid
The metal atoms lose electrons and are oxidised, and the hydrogen ions from the acid gain electrons and are reduced
What happens when a acid reacts with a base
A neutralisation reaction occurs
Whta is produced in a reaction between an acid and a base
A salt and water
What do the sum of the charges on the ions in a salt add up to
Zero, this enables you to work out the formula of salts, knowing the charges on the ions present
How can a pure, dry sample of the salt made in a acid-base reaction canbe crytalised out of a solution
By evaporating off most of the water, and drying with filter papers if necessary
What is needed when a soluble salt is prepared by reacting an alkali with an acid
An indicator, the experiment can then be repeated without the indicator to make a salt, then a pure, dry sample of its crystals prepared
What is produced when a carbonate reacts with an acid
Produce a salt, water, and carbon dioxide gas
How can you test for hydrogen
Squeaky pop test (lighted splint)
How can you test for carbon dioxide
Turns lime water cloudy
What do acids produce in aqueous solutions
Hydrogen ions (H+)
What do aqueous solutions of alkalis contain
Hydroxide ions (OH-)
What are bases
Substances that will neutralise acids
What is an alkali
A soluble hydroxide
Alkali produce OH- (aq) ions when you add them to water
What can the pH scale be used for
To show how acidic or alkaline a solution is
What are solutions that have a pH value of:
Less than 7
More than 7
7
Less than 7 - aicidc
More than 7 - alkaline
7 - neutral solution
In neutralisation reaction between an acid and an alkali, how is water produced
Hydrogen ions react with hydroxide ions
H+(aq) + OH-(aq) -> H^2O(l)
How can you use the universal indictator
To find the pH of a solution. It is special indictor made from a number of dyes. It turns a range of colours as the pH changes.
What happens to a strong acid (e.g hydrochloric acid) in a aqueous solution
Completely ionised
What happens to a weak acid (e.g ethanoic acid) in a aqueous solution
Partially ionised
For a given concentration of aqueous solutions, the stronger an acid….
The lower the pH
What happens when the pH decreases by one unit
The hydrogen ion concentration of the solution increases by a factor of 10
Why are some acids described as weak (e.g prpanoic acid), whilst other are described as strong (e.g nitric acid)
Nitric acid is a strong acid because it will completely ionise in solution. This means it will split into positive H+ and negative H- ions. While, propanoic acid don’t release H+ ions into the solution.
Why is it possible to have very dilute solution of a strong acid with a higher pH value than a concentrated solution of a weak acid
This because the strong acid splits up into positive and negative hydrogen ions. While, the weak acids don’t split up. It is reversable with a weak acid
