Chemical Changes C4 Flashcards
What is oxidation/reduction
Oxidation Is loss of electrons and reduction is gain of electrons
What’s a displacement reaction
Where a more reactive metal displaces a less reactive metal from a compound
General equation for a reaction between metals and acids
Metal + acid -> salt +hydrogen
What are bases?
Compounds that neutralise acids
What are acids and alkalis
Acids produce hydrogen ions aq.
Alkalis are soluble bases and produce hydroxide ions aq.
What colour and number is neutral on the ph scale
Green, 7
What is a strong acid and what is a weak acid
Strong acid is completely ionised in aq solution
Weak acid is partially ionised in aq solution
What happens to ph as concentration of h+ increases
Ph decreases
What is electrolysis
Electrolysis involves using electricity to break down electrolytes to form elements.
What is an electrolyte
The liquid/solution that conducts electricity
What happens at the Cathode and anode and which is positive and negative
Cathode is negative electrode, Anode is positive
Reduction occurs at the cathode
Oxidation occurs at the anode
What is cryolites purpose
Lowers the melting point of aluminium oxide, reducing energy cosfs
Define Conservation of mass
the total mass of the reactants in a chemical reaction is equal to the total mass of the products
What is relative formula mass?
The sum of the relative atomic masses of the atoms in a formula
What could happen to the mass if the product or reactant is a gas
The mass could be less because the gas has seemingly escaped into the atmosphere.
The gas’s weight may not be taken into account.
What is the formula to Calculate the volume of a gas
No of moles of gas or mass of gas = volume of gas (dm3) / 24dm3
What is the limiting reactant
The reactant that is completely used up and limits the amount of product that can be made
Define concentration
the amount of solute there is in a specific volume of the solvent.
Units for concentration
Mol/dm3
Define mole
The mass of 1 mole of a substance in grams is equal to its relative formula mass. For example water has an RFM of 18 and 1 mole of water has a mass of 18g.
How to work out number of moles
Number of Moles = Mass / RFM
How to calculate concentration (2 ways)
Concentration (g/dm3) = mass of solute (g) / volume of solution (dm3)
Concentration (mol/dm3) = no. Of moles / volume of solution (dm3)
Describe the steps of the making salts RPA (6 marks)
- Add fixed volume of dilute acid into a beaker
- Heat acid into almost boiling.
- Asmall amount of copper oxide and the stir using a glass rod.
- Keep adding copper oxide into powder remains after stirring. This means all of the acid has reacted and the reaction has stopped.
- Use filtration to remove unreactive copper using filter paper and conicle flask.
- Play solution in an evaporating basin and heat gently over beaker of boiling water.
- leaves solution in a cool place for 24 hours to allow crystals to form.
