Unified Flashcards
Explain why a CF4 molecule has polar bonds but does not have an overall dipole
F is more electronegative than C but CF4 is symmetrical so the dipoles cancel
Explain why a small proportion of molecules in water have a relative molecular mass of 20
Molecules contain 2H , 3H
O/H atoms have more neutrons than 1H
Different O/H isotopes are present
Why must mixture be acidified so crystals of benzoic acid appear
Acid reacts with benzoate and carboxylate /salt to form benzoic acid
How to recrystallise impure crystals
Dissolve in minimum quantity of hot solvent
Cool and filter and leave to dry
Two modifications that student could make to method to be confident all oxygen had been removed?
Heat to constant mad
Pass ** gas through tube as it cools
Use excess gas
Bubble gas through like water
Spread / break up the metal oxide
How to test acidity
pH paper turns red / pH less than 7
No reaction with sodium carbonate
Requirement for E/Z
C = C double bond
Each C is attached to two different groups
LinkedIn to high priority groups
How to prepare standard solution
Dissolve solid in distilled water in beaker
Transfer to volumetric flask and transfer washings to flask
Mark up to 250 cm3 with water and invert flask
How to do reflux
Use deprecating funnel, organic layer at bottom
Dry with anhydrous salt like calcium chloride
Redustil at 102 C
Why does he allow solvent to evaporate and not boil off all the solvent
Prevents water of crystallisation from being removed
Anhydrous salt would form
Prevents dehyddratoon
