Studied by 0 peopleWhat is the conservation of mass?
The total mass of reactants is equal to the total amount of product
Why is mass conserved in a reaction?
Because no atoms are lost or made
What must we do to chemical equations to show the conservation of mass?
Balance it
What is a half equation used for?
To show what happens to one reactant in a chemical reaction with the electrons written as e-
What are ionic equations?
They can be used to show what happens to the species that are involved in the reaction and the spectator ions are not included
What is the species in chemistry?
The different atoms involved in a reaction
What is the relative formula mass of a substance?
The sum of all the relative atomic masses in a substance
Why may some reactions appear to change in mass?
When a reaction is carries out in a non-closed system and involves a gas that can leave or enter the system
What is a mole (Mol)?
A measure of the number of particles contained in a substance
How many particles are in one mol?
6.02 x 10 to the power of 23
What is the constant value for one mol known as?
Avogadro constant
How much is one mol of a substance in grams?
The relative formula mass
How do we work out the amount of moles in a substance?
mol= mass of substance (g)/atomic or formula mass (g/mol)
What is a limiting reactant?
When one chemical in a reaction is used up so stops the reaction from going any further
How much volume does one mol of any gas take up at room temperature and pressure?
24dm^3
How do we work out the volume of a gas using moles?
Amount (mol) x 24dm^3
What is the equation for the concentration of a substance?
Amount of substance (mol) / volume dm^3
How do you convert from cm^3 to dm^3?
Divide by 1000
What is a titration?
Method that finds how much acid is needed to neutralise an alkali
What is the neutralisation equation?
H+ +OH- = H2O
What indicators could you use for a titration?
Methyl orange or phenolphthalein
What two things must be known to work out the unknown concentration of an acid or alkali in a titration?
the volumes of each and the concentration of one
What is percentage yield?
The actual yield obtained from a reaction vs the theoretical yield
Why is percentage yield never 100%?
Some product could be lost, if it is reversible it may not go through to completion, some reactants may react differently than expected
How is percentage yield calculated?
Actual yield/ theoretical yield x 100
What is the atom economy?
The measure of the amount of reactants that end up as a useful or desired products
Why do scientists try and choose pathways with high atom economy?
Economic reasons, sustainable development- more made, less wasted
How is atom economy calculated?
Sum of formula mass of desired product/ relative formula mass of all reactants x100
What are the two ways ethanol can be produced?
hydration and fermentation
What happens during hydration?
Steam is reacted with ethene to give ethanol
What type of reaction is hydration?
An addition reaction- all the reactant atoms end up as the desired product
Why is hydration better than fermentation?
Because the atom economy of hydration is 100% but the atom economy for fermentation is much lower
What factors do scientists have to compare when choosing a reaction pathway?
The atom economy, cost of reactants, percentage yield, rate of reaction, equilibrium position, usefulness of by-products
What is oxidation?
The gain of oxygen or the loss of electrons
What is reduction?
The loss of oxygen or the gain of electrons
What is the order of the reactivity series?
Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead, hydrogen, copper, silver, gold, platinum
What is meant by reactivity?
How easily a substance looses electrons
What is produced when a metal reacts with an acid?
A metal salt and hydrogen
What is produced when the alkali metals react with water?
A metal hydroxide solution and hydrogen
Why does the reactivity series of metals often contain carbon and hydrogen?
For comparison
What is a displacement reaction?
A more reactive metal will displace the less reactive metal from its salt
How can metals that are less reactive that carbon be extracted from their oxides?
By heating them with carbon
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