Solutions and dilutions Flashcards
How to calculate mass of a compound?
Mass (g) = molarity (mol/L) x molecular wt (g/mol) x volume (L)
other words
g = mol/L x mwt x volume
What are the different balance types and what is the readability?
- Top pan = 0.01g/0.1g
- Analytical = 0.0001g (0.1mg)
- Semi micro = 1-10ug
- micro - 0.1ug
What are the different lab water types and what are they used for?
Grade 3 single distilled - glassware rinsing, water baths
Grade 2 double distilled - reagents, solutions
Grade 1 ultra pure - analytical procedures
How is water filtered?
Reverse osmosis, ultrafiltration, ion exchange
Different equipment to measure liquid volumes?
Worst = Pasteur pipette - 30ul-2mL, low accuracy
Best = microsyringe - 0.5 -50uL, high accuracy
Best for repeated measurements (the one we use in labs) = micropippettes - 5ul-5mL, high accuracy
What are some precautions that must be abided when handling different liquids?
- Time must be allowed for viscous liquids (like glycerol) to flow
- Be careful of evaporation with organic liquids like ethanol
- When a liquid is frothing, like proteins and detergents, be careful to avoid shaking and air bubbles
- Liquid suspensions like cells need to be settled
What equation is used when making up a series of dilutions?
C1 X V1 = C2 X V2 C1 initial conc C2 final conc V1 initial volume V2 final volume
How to work out SD?
- work out mean of values
- minus the mean from all the values and then square the answer
- do that for all the values and then find the average again
- square root the answer, thats the SD
How to work out % coefficient?
100 x standard deviation/mean
How to work out % difference?
(measured value - expected value/expected value) x 100
When is an internal control acceptable?
when the coefficient of variance is under 5% and a difference from expected is under 2%.
