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Useful Equations and Conversions
Henderson–Hasselbalch
equation
pH = pKa + log 
fraction neutralized
fraction unneutralized

 

 

pH = pKw – pKb + log 
fraction unneutralized
fraction neutralized
Beer’s law
A = Îbc = log        1      
%T/100		 = 2 – log %T
Faraday’s law
w =  i × t × equiv wt
F
Molarity
 M   =   moles of solute (mole)
liter (L) 		  =   millimoles of solute (mmole)
milliliter (mL)
Normality
N   =   equivalents (eq)
liter (L) 		  =   milliequivalents (meq)
milliliter (mL)
Assay
% A   =   mLB × FB × reaction ratio × formula wt of A (mg/mmole) × 100
sample wt (mg)

 

Parts per Million
Parts per Billion
Percent
10,000     
 ppm
1.0%
1,000     
 ppm
1,000,000
 ppb
0.1%
100     
 ppm
100,000
 ppb
0.01%
10     
 ppm
10,000
 ppb
0.001%
1     
 ppm
1,000
 ppb
0.0001%
0.1  
 ppm
100
 ppb
0.00001%
0.01
 ppm
10
 ppb
0.000001%

 

grams/milliliter (g/mL) = milligrams/microliter (mg/µL)
micrograms/milliliter (µg/mL) = nanograms/microliter (ng/µL)
parts per million (ppm) = micrograms/gram (µg/g)
= micrograms/milliliter (µg/mL)
= nanograms/milligram (ng/mg)
= picograms/microgram (pg/µg)
= 10–6
parts per billion (ppb) = nanograms/gram (ng/g)
= nanograms/milliliter (ng/mL)
= picograms/milligram (pg/mg)
= 10–9

 

Composition of Concentrated Reagent-Grade Acids and Ammonium, Potassium, and Sodium Hydroxide Solutions

Concentrated Reagent
Formula
Formula
Weight
Approximate
Strengtha
(% w/w)
Assay Limits
(% w/w)
Molarity
(M)
Quantity To
Prepare 1 L of
1 M Solutionb
(mL)
Normality
(N)
Quantity To
Prepare 1 L of
1 N Solutionb
(mL)
Acetic acid
CH3COOH
60.05
99.8
≥99.7
17.4
57.5
17.4
57.5
Formic acid
HCOOH
46.03
90.0
88.0–96.0
23.6
42.5
23.6
42.5
Hydrochloric acid
HCl
36.46
37.2
36.5–38.0
12.1
82.5
12.1
82.5
Hydrofluoric acid
HF
20.01
49.0
48.0–51.0
28.9
34.5
28.9
34.5
Nitric acid
HNO3
63.01
70.0
68.0–70.0
15.9
63.0
15.9
63.0
Perchloric acid
HClO4
100.46
70.5
69.0–72.0
11.7
85.5
11.7
85.5
 
61.3
60.0–62.0
9.5
105.5
9.5
105.5
Phosphoric acid
H3PO4
98.00
85.5
≥85.0
14.8
67.5
44.4
22.5
Sulfuric acid
H2SO4
98.08
96.0
95.0–98.0
18.0
55.5
36.0
28.0
Ammonium hydroxide
asNH3
35.05
29.0
28.0–30.0
14.5
69.0
14.5
69.0
Potassium hydroxide
KOH
56.11
45.0
≥85.0
11.7
85.5
11.7
85.5
Sodium hydroxide
NaOH
40.00
50.5
≥97.0
19.4
51.5
19.4
51.5

aRepresentative value.
bRounded to nearest 0.5 mL.
Source: Reproduced courtesy of Mallinckrodt Baker, Inc.