Chapter 3 Flashcards
Definition of relative molecular mass, Mr
Compares the mass of a molecule with 1/12th of the mass of an atom of carbon-12.
Definition of relative formula mass
Compares the mass of a formula unit with 1/12th of the mass of an atom of carbon-12.
What does a hydrated salt contain?
Is an ionic solid which contains water of crystallisation as part of their structure.
How do you calculate the formula of a hydrated salt?
Heat a known amount of hydrated salt ‘to constant mass’ in a crucible. For the ionic part its mass of crucible+hydrated salt - mass of crucible. For water its crucible+hydrated - crucible+anhydrous
What are some errors when doing the hydrated salt experiment?
Not all water of crystallisation is removed - value is less than it should be. Further decomposition of ionic compound could occur.
Definition of concentration.
The amount of solute dissolved in each 1dm3 of solution.
At RTP what volume of 1 mole of any gas occupy?
24dm^3.
Volume = moles x (gas constant) 24
When is a gas said to be ideal?
The particles are in random motion, have negligible size, collisions are elastic, and there are no intermolecular forces
What is the ideal gas equation?
pV=nRT
p in Pa, V in m^3, n = no. moles, R = gas constant 8.314, T in K (Celsius+273).
What is the limiting reagent?
It’s completely used up in reaction and determines the maximum amount of product that can be formed.
What is the theoretical yield and why is it difficult to achieve?
All limiting reactant has reacted and been converted to products. But the reaction may not have gone to completion, side reactions may have taken place, purification of the product may result in loss of some product.
What is the formula for % yield?
Actual
———— X 100
Theoretical
Formula for % atom economy and definition.
A measure of how well the atoms have been utilised.
Sum of mr desired products
—————————————- X 100
Sum of mr all products
