Chapter 5 Flashcards
How many particles are there in 1 mole?
6.02 x 10^23
What is Avagadro’s constant?
The number of particles in 1 mole
What is the formula for the number of moles in terms of particles?
Moles = number of particles you have / Avagadro’s constant
What is the molar mass?
The mass per mole of something
Is the molar mass the same as the relative molecular mass?
Yes
What is the equation for moles in terms of molar mass?
Moles = mass of substance / molar mass of substance
What is the equation for moles in terms of concentration?
Moles = concentration x volume
What is concentration usually measured in?
Moles / dm^3
What does the empirical formula give you?
The smallest whole number ratio of atoms
What does the molecular formula give you?
The actual number of atoms in each type of elements in a molecule
What is the percentage composition of an element?
(The total mass of the element in a compound / total mass of compound) X 100
What do ionic equations show?
The reacting particles only
How do you work through an ionic eqution?
Rewrite the equation to just the ions, cross out any ions that are the same on both sides
What happens in a displacement reaction?
On element replaces another
When bases react with acids, what are always produced?
Water and a salt, and sometimes carbon dioxide
In precipitation reaction, what is formed?
A solid
At room temperature, how much volume does 1 mole of every gas take up?
24 dm^3
How do you work out the number of moles of a gas?
Volume in dm^3 / 24dm^3
What is the ideal gas equation?
pV = nRT
What is the value of R, the gas constant?
8.31 J k-1 mol-1
In the ideal gas equation, what is the volume recorded in?
m^3
What is a hazard?
Anything that has potential to cause harm or damage
What is the risk associated with a hazard?
The probability of someone being harmed if they are exposed to the hazard
What is a risk assesement?
Working out how likely it is that something could go wrong, and then thinking of ways to reduce the risk
Why do we do titrations?
To work out the amount of an acid i required to neutralise an alkali
What is the use of a pipette
To measure the exact volume of a solution
What is the use of a burette?
A device which allows you to measure different volumes and add the solution drop by drop
Why do you start with a rough titration?
To get an idea of where abouts the end point is
What is the titre?
The amount of acid used to neutralise the alkali
How long should you repeat the titration for?
Until you get answers that are concordant (similar to each other).
What do indicators do?
They change colour very quickly over a small pH change
What does the indicator methyl orange do when adding acid to alkali?
Turns yellow to red
What does the indicator phenolphthalein do when adding acid to alkali?
It turns red to colourless
Why is it best to do a titration on a white surface?
So the colour change is easy to see
Why are universal indicators not very useful in titrations?
Because the colour changes gradually over a wide pH range
What is the formula of hydroxide?
OH-
What is the uncertainty?
The amount of error you might have in a measurement
What is the percentage uncertainty?
(Uncertainty / reading ) X 100
What is the best way to reduce percentage uncertainty?
Use more precise equipment and use more volume of a liquid
What are systematic errors?
Errors caused by the set-up or equipment used
What are random errors?
Errors that make the result a little bit different each time
What is the best way to deal with random errors?
Repeat the experiment a few times and find a mean value
How do you find the total percentage uncertainty?
Add up all the individual uncertainties together
What is the percentage?
(actual yield / theoretical yield) X 100
What is the atom economy?
A measure of the efficieny of a reaction
How do you calculate the atom economy?
( Molar mass of desired product / molar mass of all products ) X 100
What is an addition reaction?
A reaction where the reactants form only 1 product
