Experiments and practicals Flashcards
Why do we stir solutions with a thermometer during experiments when recording temperature?
To ensure uniform temperature.
Why is the mass of the solid ignored when doing specific heat capacity calculations/ experiments?
The solid has negligible specific heat capacity (or mass, usually this is rejected)
Why is the temperature of a solution measured for a period of time prior to adding a reactant?
To ensure (thermal) equilibrium
Why is the temperature of a solution measured for a period of time after adding a reactant?
To allow for cooling
Why are polystyrene containers used in SHC and enthalpy experiments?
They are thermal insulators
What do we use to measure fixed volumes for titrations and other experiments
Pipette
How do we weigh by difference?
-add reactant to a weighing boat
-find mass of weighing boat and reactant with mass balance
-remove reactant
-reweigh weighing boat
-calculate mass difference
When esters are made, a H2SO4 catalyst is added dropwise to a reaction in an ice bath. Why?
The reaction is exothermic and vigourous. Adding it quickly would be dangerous. It prevents splashing/loss of volatile compounds
Why is reflux used?
It allows heating for a long period of time and prevents loss of reactants.
A reaction is heated for a long period of time to equilibrium, and at eqm., components are removed.
Why is reflux performed for a long time?
To allow eqm. to be reached and ensure maximum yield.
What could be used to remove acid from an impure mixture?
Calcium carbonate
Why must pressure be released in intervals after calcium carbonate has been added to remove acid from an impure mixture?
Acid reacts with carbonate ions to produce CO2 gas
Name a drying agent
CaCl2, MgSO4
anhydrous
How does appearance of an organic liquid change upon addition of a drying agent?
Turns clear
Why are anti bumbing granules used?
Ensures smooth/even boiling/heating
