Quantitative Chemistry Flashcards
What do you compare an element to, to get its relative atomic mass
Carbon-12
When can changes of mass occur in a reaction
In a non-closed system
Example of a non-closed system losing mass
When a gas is produces
If everything is included in the reaction calculation
The mass stays the same
What is uncertainity in a experiment
Measure of variability
2 ways of measuring uncertainty
Use the range of results or the resolution of the equipment you used
Types of error
Random error, systematic error
What are random errors
Errors that cannot be predicted and are random
Examples of random errors
Human error for example technique while taking measurements
Instruments are faulty
What are systematic errors
Errors that are produced consistently
Example of systematic errors
Problems with experimental method
Not adjusting a scale properly
Uncertainty equation
Uncertainty = range of results/2
To measure concentration you must
Work in Dm3 for volume
Dm to Cm
Dm3 to Cm3
x10
x1000
Concentration equation
Concentration = mass /volume
How many particles is one mole
6.02 x 10^23 Avagadros constant
The mass of one mole of a substance is
Equal to its relative formula mass
Symbol for Avogadros constant
N with a little A at the bottom
Number of particles in a substance equation
N = n x Avagadros constant
n= number of moles
Mass moles equation
moles = mass/Mr
Calculate the mass of water when burning 300g of Methane
- CH4 + O2 –> 2H2O + CO2
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What is a limiting reactant
The reactant that is used up first meaning the reaction can no longer take place as the other reactant(s) have nothing to react with
How to workout the maximum mass of something produced in a reaction
Workout the moles of the known
Compare that to what 1 mole of the known makes of the unknown
e.g if 1 mole of iron makes 1 mole of iron oxide then 1.5 moles of iron makes 1.5 moles of iron oxide
workout mass of unknown
Concentration moles equation
Concentration = moles/volume
