Lecture 1: Introduction to Analytical Chemistry Flashcards
TWO TYPES OF DIGITS
EXACT AND INEXACT
- NUMBERS NOT MEASURED USING INSTRUMENTS
- INCLUDES DEFINED NUMBERS
- INFINITE NUMBER OF SFS
- DOESN’T AFFECT ACCURACY/PRECISION OF CALCULATIONS OR PRECISION
EXACT NUMBERS
WHAT TYPE OF DIGITS ARE THESE?
- 1 FOOT = 12 INCHES
- 100 YRS IN A CENTURY
EXACT NUMBERS
- NUMBERS WHICH ARE MEASUREMENTS MADE WITH INSTRUMENTS
- WITH INHERENT UNCERTAINTY FROM THE INSTRUMENTS
INEXACT NUMBERS
INDICATES THE PROBABLE UNCERTAINTY IN AN EXPERIMENTAL MEASUREMENT
SIGNIFICANT FIGURES
ALL THE DIGITS THAT ARE “CERTAIN” + FIRST UNKNOWN DIGIT
SIGNIFICANT FIGURES
TRUE OR FALSE:
NON ZERO DIGITS ARE ALWAYS SIGNIFICANT
TRUE
TRUE OR FALSE: ZERO IS SIGNIFICANT WHEN IT IS BETWEEN 2 NON-ZERO DIGITS
TRUE
TRUE OR FALSE:
THE FINAL/TRAILING ZEROS OF A NUMBER IS SIGNIFICANT
FALSE
- ONLY FOR THE DECIMAL PORTION
TRUE OR FALSE:
ZEROS BETWEEN DECIMAL POINT AND NON-ZERO DIGITS ARE SIGNIFICANT
FALSE
- THEY SERVE AS PLACEHOLDERS ONLY
ADDITION/SUBTRACTION
- ROUND ANSWER TO ______ NO. OF ______ OF ANY OF THE GIVEN NUMBERS
LEAST, DECIMAL PLACES
MULTIPLICATION/DIVISION
- ROUND ANSWER TO _______ NO. OF _______ OF ANY OF THE GIVEN NUMBERS
LEAST, SFS
SF IN LOGARITHM
NO. OF SFS IN THE ORIGINAL NUMBER = NO. OF SFS TO THE RIGHT OF DECIMAL POINT
SF IN ANTILOGARITHM
NO. OF SFS OF ANSWER = NO. OF SIGNIFICANT DECIMAL PLACES IN GIVEN
SHOULD ROUNDING OFF BE DONE DURING CALCULATIONS?
NO. AT THE END ONLY.
- ROUND OFF ONLY FINAL RESULT. PRELIMINARY ROUNDING OFF OF RESULTS IS DISCOURAGED
WHY SOULD ROUNDING OFF BE MINIMIZED DURING CALCULATIONS?
TO MINIMIZE DEVIATION OF FINAL ANSWER FROM CORRECT VALUE
INDICATE NO. OF SFS A. 0.0050 B. 3000 C. 1.5 x 10^-2 D. 500.0 E. 1.5050 x 10^3
A. 2 B. 1 C. 2 D. 4 E. 5
ROUND OFF ACCORDING TO SPECIFIED NO. OF SFS A. 15.9994 (4) B. 15.515 (4) C. 254.5 (3) D. 14.5001 (2)
A. 16.00
B. 15.52
C. 255
D. 15
PERFORM OPERATION. OBSERVE CORRECT NO. OF SFS
15.12 mL x 19.25 mL x 2.07 mL
602.4942 –> 602 (3 SF)
PERFORM OPERATION. OBSERVE CORRECT NO. OF SFS
4.5 in - 1.258 in
3,242 –> 3.2 (1 DECIMAL PLACE ONLY)
(2.34 - 1.2) x 0.105
1.1 x 0.105 = 0.1155 –> 0.12 (2 SF)
WHAT ARE THE WAYS OF EXPRESSING SOLUTION CONCENTRATION?
MMPPN
MOLARITY MOLALITY PERCENT COMPOSITION PARTS PER MILLION NORMALITY
MOLES OF SOLUTE DIVIDED BY LITERS OF SOLUTION
MOLARITY (M)
FORMULA AND UNITS OF MOLARITY
FORMULA: M = moles solute/L solution
UNITS: mol/L or M
MOLES OF SOLUTE DIVIDED BY KILOGRAMS OF SOLVENT
MOLALITY (m)
FORMULA AND UNITS OF MOLALITY
FORMULA: m = moles solute/kg solvent
UNIT: mol/kg or m
THREE TYPES OF PERCENT COMPOSITION
A. %w/w - % weight per weight
B. %v/v - % volume per volume
C. %w/v - %weight per volume
FORMULA FOR %w/w
%w/w = (g solute/g solution) x 100%
FORMULA FOR %v/v
%v/v = (mL solute/mL solution) x 100%
FORMULA FOR %w/v
%w/v = (g solute/mL solution) x 100%
FORMULA FOR ppm
EITHER %w/w or %w/v
ppm = (g solute/g solution) x 10^6
ppm = (g solute/mL solution) x 10^6
FORMULA FOR ppb
EITHER %w/w or %w/v
ppm = (g solute/g solution) x 10^9
ppm = (g solute/mL solution) x 10^
NUMBER OF EQUIVALENTS OF SOLUTE IN 1L SOLUTION
NORMALITY (N)
FORMULA FOR NORMALITY
N = no. eq solute/L solution
DESCRIBE THE AMOUNT OF A CHEMICAL SPECIES JUST LIKE MOLES
EQUIVALENTS (eq) OR MILLIEQUIVALENTS (meq)
MOLARITY: NORMALITY = MOLES: _______
EQUIVALENTS
MOLARITY: ______ = MOLES: EQUIVALENTS
NORMALITY
THIS IS THE DEFINITION OF THE “EQUIVALENT” AT THE EQUIVALENCE POINT OF ANY TITRATION
NO. OF eq ANALYTE PRESENT = NO. OF eq REAGENT ADDED
OR
NO. OF meq ANALYTE PRESENT = NO. OF meq REAGENT ADDED
WHY IS THERE NO NEED TO DERIVE THE STOICHIOMETRY BETWEEN THE ANALYTE AND TITRANT?
BECAUSE WE JUST HAVE TO CORRECTLY DEFINE THE eq OR meq FOR EACH TYPE OF REACTING SPECIES
THE AMOUNT OF SUBSTANCE CONTAINED IN ONE EQUIVALENT CAN VARY DEPENDING ON THE _________
TYPE OF REACTION
FORMULA FOR CALCULATING THE NUMBER OF EQUIVALENTS PRESENT IN A SAMPLE
no. eq = mass in g/EW
EW = EQUIVALENT WEIGHT OF ANALYTE
WHAT IS EW?
EQUIVALENT WEIGHT OF THE ANALYTE
FORMULA FOR CALCULATING THE EW
EW = FW/n
FW = FORMULA WEIGHT OF ANALYTE n = FACTOR THAT DEPENDS ON TYPE OF CHEMICAL REACTION
THIS IS THE FACTOR THAT DEPENDS ON THE TYPE OF CHEMICAL REACTION BETWEEN ANALYTE AND TITRANT
factor n
THIS CAN BE USED TO CONVERT MOLARITY TO NORMALITY AND VICE VERSA
factor n
HOW IS THE RELATIONSHIP OF M AND N EXPRESSED IN AN EQUATION
N = n x M
TYPES OF CHEMICAL REACTION BETWEEN THE ANALYTE AND THE TITRANT
CARP
COMPLEXATION
ACID-BASE (NEUTRALIZATION)
REDOX
PRECIPITATION
FOR A NEUTRALIZATION REACTION, WHAT IS n?
NUMBER OF H+ IONS THAT AN ACID DONATES OR THAT A BASE ACCEPTS
FOR A PRECIPITATION REACTION, WHAT IS n?
CHARGE OF CATION OR ANION PARTICIPATING IN THE REACTION
FOR A COMPLEXATION REACTION, WHAT IS n?
NUMBER OF ELECTRON PAIRS A METAL ACCEPTS OR A LIGAND DONATES
FOR A REDOX REACTION, WHAT IS n?
NUMBER OF ELECTRONS RELEASED BY THE REDUCING AGENT OR ACCEPTED BY THE OXIDIZING AGENT
GIVEN REACTION:
H2SO4 + 2NH3 -> (2NH4)+ + (SO4)2-
type of reaction = ?
n of acid = ?
n of base = ?
type of reaction = ACID-BASE / NEUTRALIZATION
n of acid (H2SO4) = 2
DONATES 2 PROTONS
n of base (NH3) = 1
ACCEPTS 1 PROTON
GIVEN REACTION:
Pb2+ + 2I- -> PbI2
type of reaction = ?
n of Pb2+ = ?
n of I- = ?
type of reaction = PRECIPITATION
n of Pb2+ = 2
CHARGE OF PB2+ = 2
n of I- = 1
CHARGE OF I- = 1
GIVEN REACTION:
Ag+ + 2NH3 -> Ag(NH3)2+
type of reaction = ?
n of metal = ?
n of ligand = ?
type of reaction = COMPLEXATION
n of metal (Ag+) = 2
n of ligand (NH3) = 1
GIVEN REACTION:
2Fe3+ + Sn2+ -> Sn4+ + 2Fe2+
type of reaction = ? RA = ? OA = ? n of RA = ? n of OA = ?
type of reaction = REDOX
RA = Sn2+ OA = Fe3+
n of RA = 2
n of OA = 1
THESE ARE IMPORTANT IN SOLUTION PREPARATION
DILUTIONA ND ALIQUOT FACTORS
IN SOLUTION PREPARATION, KEEP IN MIND WHICH BETWEEN ______ AND ______ IS HELD CONSTANT FOR EACH PROCESS
NUMBER OF MOLES, CONCENTRATION
IN DILUTION, ______ IS KEPT CONSTANT
NUMBER OF MOLES
IN GETTING ALIQUOTS, ______ IS KEPT CONSTANT
CONCENTRATION
IMPORTANT EQUATIONS IN DILUTION
M x V = n = constant
M1V1 = M2V2 = M3V3
IN GETTING ALIQUOTS, WHY IS THE NUMBER OF MOLES NOT HELD CONSTANT?
GETTING ALIQUOTS = GETTING A PORTION OF THE SOLUTION –> THIS HAS LESS MOLES THAN THE WHOLE
WHAT ARE THE STEPS IN CHEMICAL ANALYSIS?
SOPAC
- SELECT METHOD (appropriate and reliable)
- OBTAIN GROSS SAMPLE FROM BULK
- PROCESS SAMPLE
- ANALYSIS
- CALCULATIONS AND REPORT DATA
IN SELECTING AN ANALYTICAL METHOD, IT MUST BE FIT FOR THE ______
PURPOSE
DIFFERENT SOURCES OF ANALYTICAL METHODS
BIPS
- BOOKS (published by professional organizations_
- IN-HOUSE
- PUBLISHED (in open scientific literature)
- STANDARD ORGANIZATIONS
FACTORS IN CHOOSING A METHOD
CASES SLAPS
- COST
- ANALYSIS TIME
- SAFETY
- EQUIPMENT REQUIRED
- SAMPLE SIZE
- SENSITIVITY
- LIMIT OF DETECTION
- ACCURACY
- PRECISION
- SPECIFICITY AND SELECTIVIITY
FACTORS IN CHOOSING A METHOD:
FUNDING SUPPORT
COST
FACTORS IN CHOOSING A METHOD:
CLOSENESS TO TRUE VALUE (ABS AND REL ERROR)
ACCURACY
FACTORS IN CHOOSING A METHOD:
SMALLEST CONCENTRATION THAT CAN BE DETECTED
LIMIT OF DETECTION
FACTORS IN CHOOSING A METHOD:
CLOSENESS TO INDIVIDUAL DATA
PRECISION
THESE ARE USED TO EVALUATE PRECISION OF DATA
s, RSD, CONFIDENCE INTERVAL
FACTORS IN CHOOSING A METHOD:
TO MINIMIZE EFFORT AND COST
ANALYSIS TIME
FACTORS IN CHOOSING A METHOD:
ABILITY TO DISCRIMINATE BETWEEN ANALYTE WITH INTERFERENCES PRESENT IN THE SAMPLE MATRIX
SPECIFICITY AND SELECTIVITY
FACTORS IN CHOOSING A METHOD:
CAPABILITY OF METHOD TO RESPOND RELIABLY AND MEASURABLY TO CHANGES IN ANALYTE CONCENTRATIONS
SENSITIVITY
FACTORS IN CHOOSING A METHOD:
COST, AVAILABILITY
EQUIPMENT REQUIRED
FACTORS IN CHOOSING A METHOD:
SINCE SOME METHODS REQUIRE LARGER AMOUNT OF SAMPLE THAN OTHERS
SAMPLE SIZE
FACTORS IN CHOOSING A METHOD:
FOR THE WELFARE OF RESEARCHER/EXPERIMENTER
SAFETY
PROCESS OF SELECTING PORTION OF MATERIAL TO REPRESENT OR PROVIDE INFO ABOUT A LARGER BODY OF MATERIAL
SAMPLING
LARGER BODY OF A MATERIAL WHERE A REPRESENTATIVE SAMPLE IS TAKEN
BULK/BULK SAMPLE
PROCESS TO OBTAIN REQUIRED SAMPLE SIZE APPROPRIATE FOR ANALYSIS
SAMPLING
THIS IS DONE IN SAMPLING TO SIMPLIFY THE ANALYSIS
REDUCING SIZE OF BULK SAMPLE TO A HOMOGENOUS LAB SAMPLE
BULK SAMPLE –> GROSS SAMPLE –> LAB SAMPLE
SAMPLING
REPRESENTATIVE OF THE BULK
SAMPLE
MUST BE TAKEN INTO ACCOUNT WHEN SAMPLING
STATE OF PARENT MATERIAL
TWO TYPES OF SAMPLES
HHDS
HOMOGENOUS
HETEROGENOUS
DYNAMIC
STATIC
TYPE OF SAMPLE:
BREAKFAST CEREAL
HETEROGENOUS
TYPE OF SAMPLE:
VEGETABLE OIL AT 400C
HOMOGENOUS
TYPE OF SAMPLE WHEREIN THE COMPOSITION OF PARENT MATERIAL IS PERMANENT WRT SPACE AND TIME
STATIC
TYPE OF SAMPLE WHEREIN PARENT MATERIAL IS CHANGING WITH TIME
DYNAMIC
TYPE OF SAMPLE:
WAREHOUSE STOCK OF FOOD, OIL IN A DRUM
STATIC
TYPE OF SAMPLE:
BLOOD, RIVER WATETR
DYNAMIC
TYPE OF SAMPLE WHEREIN REMOVAL OF A PORTION OF PARENT MATERIAL AT ANY INSTANT REPRESENTS ONLY A SNAPSHOT OF THAT MOMENT IN TIME AND IN THAT PARTICULAR LOCATION
DYNAMIC
TYPES OF SAMPLING
RANDOM AND SELECTIVE
TYPES OF RANDOM SAMPLING
SSS
SIMPLE
STRATIFIED
SYSTEMATIC
TYPE OF SAMPLING WHEREIN ANY SAMPLE HAS AN EQUAL CHANCE OF SELECTION
SIMPLE
TYPE OF SAMPLING WHEREIN LOT IS DIVIDED AND RANDOM SAMPLES ARE COLLECTED FROM EACH DIVISION
STRATIFIED
TYPE OF SAMPLING WHEREIN RANDOM WITHIN TARGET GROUPS
STRATIFIED
TYPE OF SAMPLING THAT IS BEST WHEN WHOLE POPULATION IS AVAILABLE
SIMPLE
TYPE OF SAMPLING THAT IS BEST WHEN THERE ARE SUBGROUPS TO INVESTIGATE
EX: DEMOGRAPHIC GROUPINGS
STRATIFIED
TYPE OF SAMPLING WHEREIN FIRST SAMPLE IS SELECTED AT RANDOM THEN SUBSEQUENT SAMPLES ARE TAKEN ACCORDING TO A PREVIOUSLY ARRANGED INTERVAL (EVERY nth PERSON)
SYSTEMATIC
TYPE OF SAMPLING THAT IS BEST WHEN A STREAM OF REPRESENTATIVE SAMPLES ARE AVAILABLE
SYSTEMATIC
TYPE OF SAMPLING:
RAFFLE DRAW
SIMPLE
TYPE OF SAMPLING:
REGIONAL RAFFLE DRAWS
STRATIFIED
TYPE OF SAMPLING:
TAKE EVERY 50TH BOTTLE IN A PRODUCTION LINE FOR QUALITY CONTROL ANALYSIS
SYSTEMATIC
