Experiment 1 Flashcards
Solution
a homogenous mixture of solute and solvent
Percentage by mass
mass of solute / mass of solution x 100%
Molality
moles of x / mass of solvent in kg
Molarity
moles of x / volume of solution in L
Volumetric flasks
-Common sizes: 50, 100, 250, and 500 mL
-Weigh out solids material and transfer it to the flask by adding it through small funnel and rise with solvent so that rinsings are including (quantitative transfer)
-Fill carefully to mark with solvent, stopper securely, and mix by inverting 10 times
-Do not fill it to the mark
-Flask must be dry if calculating molality (uses mass)
Volumetric pipets
-Calibrated to deliver a fixed volume of liquid with high precision
-Common sizes: 0.05, 10, even 200 mL
-Pipet must be kept clean so it drains without beading
-Graduated pipette will have greater error in volume measurement than volumetric pipette that are designed to deliver a specific volume
-Never blow air into pipet (introduce dirt and cause beading)
-Always rinse/rotate a pipet with solution to be delivered (conditioning)
-Draw liquid above calibration mark
Burets
-A graduated tube with a stopcock and a tip commonly used for titrations
-Make sure stopcock fits tightly
-Always record initial and final volumes (difference is volume of titrant being delivered)
-Often has 50 mL capacity and has 0.1 mL increments
-Buret should drain without beading
-Rinse buret with small (2-3 mL) portions of the titrant solution, then fill above the zero line and drain slowly just below zero
-Remove air bubbles trapped in the tip by rapidly turning the stopcock several times
-To read buret, use white notecard with straight black line to locate bottom of meniscus
-Maximum error is 50 mL buret is +/- 0.05 mL
How dirty glassware can affect measurements
-If buret/vol. pipet delivers solution but then appears dirty (droplets stuck to inside), these droplets represent volume that was expected to have left glassware
-This means that actual volume of solution delivered is less than recorded
