C3 - Quantitative chemistry

What 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