freesciencelesosns chemistry Flashcards
What is ionising
when a acid molecule splits
What is a strong acid
an acid that fully ionises in an aqueous solution
Three examples of strong acids
hydrochloric acid
Sulfuric acid
nitric acid
what is a weak acid
Weak acids partially ionise in aqueous solution
three examples of weak acids
Carbonic acid
ethanoic acid
citric acid
What does the pH scale tell us about the concentration of hydrogen ions in acids
As the pH scale decreases by one unit, the concentration of hydrogen ions increases by ten times
What is a compound
compounds contain two or more different elements chemical combined in a fixed proportion
How to separate a compound back into its elements
you need to use a chemical reaction to do this
Define mixture
a mixture has different elements/compounds not chemical combined together
How to separate a mixture
use a physical technique, rather than a chemical reaction Filtration distilation Crystallisation chromatography
What is a molecule
a molecule has any elements chemicaly joined
What happens when we react an acid with a base or an alkali
we make a salt and water
What happens when we react an acid with a metal carbonate
they make a salt, water and carbon dioxide
What is a polymer made of
thousands of small identical molecules joining together (called monomers)
what are the two types of polymers
Addition polymers and condensation polymers
how to name polymer
The word poly followed by the name of the monomer
what does the word poly mean
many
What are addition polymers formed form
they are formed from alkenes
All of the atoms in the monomer end up in the polymer
How are condensation polymers made
they are made from monomers, but they are not alkenes
When these monomers react, we lose small molecules such as water
How does the reactivity series work in displacement
a more reactive element will push out a less reactive element from its compound
What is reduction
The loss of oxygen and the gain of electrons
what is oxidation
The gain of oxygen and the loss of electrons
OILRIG
Oxidation is loss
reduction is gain
Can solid ionic compound conduct electricity
no, the ions are locked in place and are not free to move
What happens when an ionic compound is melted or dissolved in water
The forces of attraction are broken and the ions are free to move
these liquids and solutions can now conduct electricity
Scientists call these liquids or solutions electrolytes
Describe cathode and anode
cathode covered with electrons (attracts positives)
Anode lack of electrons (attracts negatives0
name an important use for ammonia
To make nitrogen based fertilisers for farming
What are the raw materials for the Harber process
nitrogen and hydrogen
N2(g) + 3H2(g) = 2NH3(g)
Reversible reaction
define catalyst
catalysts increase the rate of reaction but are not used up during the reaction
This saves money because it makes reactions faster without needing temperature increase
You can reuse catalysts
how to change the direction of reversible reactions
By changing the conditions
giant covalent molecules properties
Giant covalent molecules are always solids at room temperature
they have millions of strong covalent bonds
They always have high melting and boiling points
How is diamond formed
it is formed from carbon
each carbon atom is connected to four covalent bonds to other carbons
It can’t conduct because there are no free electrons
Silicon dioxide properties
high melting and boiling point
covalent bond between oxygen and silicon
A huge number of strong covalent bonds must be broken and this takes a great deal of energy
Reactivity series
potasisum Sodium lithium calcium Magnesium aluminium
carbon
Zinc
iron
copper
how is aluminium extracted
Aluminium is extracted from the compound aluminium oxide by electrolysis
alumium oxide melting point
2000 oC
what does cryolite do
Cryolite lowers melting point
electrolysis reaction of aluminium oxide
Al3+ 3e- —> Al
Reduction
Why is electrolysis expensive
melting the compounds requires a great deal of energy
A lot of energy is required to produce the electric current
what atoms are Nobel gasses
Group zero
properties of Nobel gas
They are unreactive because they have full outer shells
Their boiling points are lower than rtp
their boiling points increases as the relative atomic mass increases
define the term proton number
number of proton
protons in the nucleus (of an atom)
Explain why the chemical properties of Mg 24/12 and Mg 26/12 (isotopes) are the same
same number of electrons
(same number) of electrons in the outer shell
suggest the differences in the melting point and boiling point with an impure substance compared to a pure substance
melting point decreases
boiling point increases
State three properties of transition elements
It has variable oxidation states
they act as catalysts
They form coloured compounds
State the full name of the compound of copper that can test for water
anhydrous copper (II) sulfate
it turns from white to blue in the presence of water
Define the term acid
proton donor
conditions to keep the same during practicals
Volume, concentration, temperature, mass, size
How to obtain pure crystals
evaporation
the starting of crystallisation
drying the crystals
What is meant by the term precipitate
a solid which forms when two solutions are mixed / reacted / added
What is the general formula of alkenes
Cn H2n
How are tiny insoluble particles removed from water during the purification process?
chemicals are added to the impure water which cause tiny insoluble particles to clump together and settle out
What can be used to identify whether a sample of water is hard or soft?
Soap solution is added drop by drop and the water sample is shaken. The more drops it takes to get a stable lather (bubbles) the harder the water is.
What ions cause hardness in water?
hardness in water is caused by calcium and magnesium ions.
What dissolved compound is responsible for causing temporary hardness in water?
Calcium hydrogencarbonate causes temporary hardness in water.
Slag forms as a waste product in the production of iron. What is slag?
Slag is calcium silicate
What is the name of the process that uses plants to extract metals from an ore?
Phytoextraction is the process that uses plants to extract metals from an ore.
What is a disadvantage of bioleaching?
The bacteria used in bioleaching produce sulfuric acid as a by-product.
What colour change could occur when hydrochloric acid is added to an alkaline solution containing universal indicator?
When hydrochloric acid is added to an alkaline solution containing universal indicator, the colour could change from purple to red.
What is the general equation for the reaction of a metal with an acid?
The general equation for the reaction of a metal with an acid is: metal + acid → salt + hydrogen
What products are formed when hydrochloric acid reacts with copper carbonate?
The products of the reaction between hydrochloric acid and copper carbonate are copper chloride, water and carbon dioxide.
Natural rainwater has a pH of 5. The most acidic rain ever recorded in Britain was 1000 times more acidic than natural rainwater. What was its pH? - Higher
The pH is 2
What mass of iron will be made when 16g of Fe2O3 reacts in the thermite reaction Fe2O3 + 2Al → 2Fe + Al2O3?
The number of moles of iron oxide reacting is given by 16 / 160 = 0.1. The balanced equation shows there will be 0.2 moles of Fe made, so the mass is 0.2 x 56 = 11.2 g. You needed to divide the starting mass by the Mr of iron oxide.
