3: Laboratory Math Flashcards
Four Rules for Significant Figures
1) Non-zeros are always significant
2) Any zeros between non-zeroes are significant
3) Leading zeros are never significant
4) Trailing zeros are only significant if the # contains a decimal
Mass Conversions
1 g = 1,000 milligram (mg)
1 mg = 1,000 micrograms (mcg or µg)
1 µg = 1,000 nanograms (ng)
1 ng = 1,000 picograms (pcg)
THINK this order in powers of 3: g –> mg –> µg –> ng –> pg
Converting between Analytical Units and SI units
To SI units: (µg)/(mL ) x CF= (µmol)/L
From SI units: (µmol)/L ÷ CF= (µg)/(mL )
(Help to remember?? RHYME THIS: FROM SI? DIVIDE!)
Step 1: calculate conversion factor (CF) –> CF = 1,000 ÷ MW
REMEMBER UNITS!!! (µg)/(mL ) and (µmol)/L
sequence of dilutions created using same dilution factor; often used for calibration curves
Serial Dilution
measured by controls; how close are you to actual true values?
Accuracy
measured by correlation coefficient (r2); how small is the variance?
Precision
what impacts on precision and accuracy come from human judgements?
Bias
36.52 mg =
36520 mcg
36520 ng
0.3652 g
0.03652 mcg
36520 mcg
A 1 mL urine sample undergoes three 10-fold serial dilutions. A final volume of 1 mL is obtained. The total Dilution Factor is:
300
10
1000
30
3
1000
The molarity of an aqueous solution of NaF is defined as the:
Moles of NaF per liter of water
Moles of NaF per mL of solution
Grams of NaF per mL of water
Moles of NaF per liter of solution
Grams of NaF per liter of water
Moles of NaF per liter of solution
How many significant figures are in the measurement 102.400 mL?
6
Solve 3.12 g + 0.8 g + 1.033 g =
5
4.96 g
4.9 g
5.0 g
4.953 g
5.0 g
(same # of SF as number with least # SF)
the ratio between the concentration of a compound being analyzed and the response of the detector to that compound
response factor
Volume Conversions
1 L = 1,000 mL
100 mL = 1 dL
1 mL = 1,000 mcL or µL
