CHAPTER 3 - AMOUNT OF SUBSTANCE Flashcards
What is the Avogrado constant?
6.02 x10^23
The number of partices in each mole of Carbon-12
What is the equation to calculate moles?
Mass (m)/Molar mass (Mr)
(Mr M(e)n)
(Worked equation page 23)
What is molecular formula?
Number of atoms of each element in a molecule
What is empirical formula
Simplest whole-number ratio of atoms of each element in a compound
What is relative molecular mass?
Compares the mass of a molecule with the mass of an atom of carbon-12
What’s relative formula mass?
The mass of a formula unit compared with the mass of an atom of Carbon-12
Describe the practical method to find out the formula of a hydrated salt
Weigh an Empty crucible
Add hydrated salt into the weighed crucible. Weigh the crucible and the hydrated salt
Using a pipe-clay triangle, support the crucible containing the hydrated salt on a tripod.
Heat the crucible and contents gently for about one minute, then heat strongly for a further three minutes
Leave the crucible to cool. Then weigh the crucible and anhydrous salt
How to work out the formula of a hydrated salt
Calculate the amount, in mol, of anhydrous CuSO4.
Calculate the mass and amount, in mol, of water
Find the smallest whole-number ratio
Write down the value of x and the formula of hydrated CuSO4
(worked example pg 24)
What are two assumptions that have been made during the calculation of Formula of Hydrated salt (Water of Crystallisation)
1 - All of the Water has been lost
2 - No further Decomposition
A student carried out an experiment to calculate the water of crystallisation of two hydrated salts. For the first salt, the student did not remove all the water of crystallisation. For the second salt, the student removed all of the water of crystallisation but unfortunately the salt composed further.
For each salt, explain whether the students calculated value of x, the number of water molecules in the formula unit, would be greater or smaller than the actual value of x in data books
The first salt would not lose all H2O so x would appear to be smaller than it should be
The second salt loses more mass than just water so x would appear to be greater than it should be
Unit conversions Between a cubic centremetre to millilitre
to Cubic decimetre to litre
1 cm3 = 1ml
1000ml = 1 litre
1dm3 = 1000ml = 1 Litre
How would you work out the Concentration of a solution
c = n/V
(worked solution page 26)
What is a standard solution?
A solution with a known concentration
What is molar gas volume?
he volume per mole of gas molecules at a stated temperature and pressure
What does RTP mean?
Room Temperature and Pressure