Chapter 5 - Steven Flashcards
What is a mole?
A large number of particles
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 equation for the number of moles?
Particles you have / Particles in 1 mole
What is the mass / molar mass equal to?
The number of moles
What is the molar mass?
The relative molecular mass
What is the unit for the molar mass?
g / mol
What are the 2 units that the concentration can be measured in?
g/dm^3 and moles/dm^3
What is the equation for concentration?
Moles / Volume or mass / volume
What is the volume recorded in?
dm^3
What is 1dm^3?
1000cm^3
What is the empirical formulae?
The simplest ratio of atoms in a compound
What is the molecular formula?
The actual numbers of each atom in a compound
What is the % composition of an element?
Mass of element / Mass of total compound X 100
What do balanced equations have?
Equal numbers of each atom on both sides
What do ionic equations show?
The reacting particles
How do you write an ionic equation?
- Break up the equation into ions
- Cross out any ions that are on the same side
What does the reaction stoichiometry show you?
The molar ratios
What does the state symbol ‘s’ stand for?
Solid
What does the state symbol ‘g’ stand for?
Gas
What does the state symbol ‘l’ stand for?
Liquid
What does the state symbol ‘aq’ stand for?
Aqueous
What does aqeous mean?
Solution in water
What happens in a displacement reaction?
A more reactive element reacts to take the place of a less reactive element
When bases react with acids, what are the products?
A salt and water
In a precipitation reaction, what is formed?
A solid
What is the molar gas volume?
The space that 1 mole of gas occupies at a certain temperature and pressure.
How many dm^3 does 1 mole of gas occupy in room temperature?
24dm^3
What is the volume / molar gas volume?
The number of moles
What is the equation of the ideal gas equation?
pV = nRT
What does the unit ‘p’ stand for?
Pressure
What is pressure recorded in?
Pascals
What does V stand for?
Volume
In the ideal gas equation, what is the volume recorded in?
m^3
What does n stand for?
The number of moles
What is the temperature recorded in in the ideal gas equation?
Kalvin
How to you work out what the temperature in Kelvin?
273 + C
What does R stand for?
The gas constant
What is the value of the gas constant?
8.31 K/K/mol
What is a hazard?
Anything that has the 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.
List 4 ways you can reduce the risk of being chemically burned:
- Using a lower concentration of acid
- Wear gloves
- Wear a lab coat
- Use goggles
What does a titration show you?
Exactly how much of an acid is needed to neutralise an alkali.
How do you do a titration?
- Measure some alkali and put it in a flask along with some indicator
- Fill burette with acid
- Add the acid to the alkali until you find the end point
- Work out the amount of acid required to neutralise the alkali
In a titration, when do indicators change colour?
When the acid has been neutralised
What does methyl orange do when the acid has been neutralized?
Turns yellow to red
What does phenolphthalein do when the acid has been neutralized?
Turns from red to colourless
Why is it best to put the flask from a titration on a white surface?
So you can clearly see the colour change.
What is the uncertainty?
The amount of error in the measurements you have.
What causes uncertainty?
The limits to the sensitivity of the equipment you used
As there is a mark every 0.1cm^3 for a 50cm^3 buretter, what is the uncertainty?
+ or - 0.05cm^3
What is the percentage uncertainty?
Uncertainty / reading X 100
List 2 ways you can reduce uncertainty:
- Use more precise equipment
- Use a larger volume of liquid
What are systematic errors caused by?
The set-up or equipment you used
Give an example of a random error:
Estimating between 2 marks
Does repeating an experiment help get rid of random errors?
Yes
Does repeating an experiment help get rid of systematic errors?
No
How do you calculate total % uncertainty?
Add up the % uncertainty of each instrument you used.
What is the percentage yield?
Actual yield / theoretical yield X 100
What is the atom economy?
Mr of desired products / Mr of all products X 100
