1. 209201 Chemical Stoichiometry
References :
Basic Principles and Calculations in Chemical Engineering, 7 edition, David. M. Himmerblau and James B. Riggs.
ปริมาณสัมพันธ์สำหรับงานอุตสาหกรรม เล่ม 1, รศ. ดร. อนันต์เสวก เห่วซึงเจริญ, ภาควิชาเคมีอุตสาหกรรม, คณะวิทยาศาสตร์, มหาวิทยาลัยเชียงใหม่.

2. Introduction

3. Dimensions, Units and Their Conversion
Dimensions : basic concepts of measurement e.g. length, time, mass, temperature, etc.

4. Fundamental (Basic) Dimensions
Dimensions that can be measured independently and are sufficient to describe essential physical quantities.
Length, Time, Mass, Temperature,
Molar amount

5. Derived Dimensions
Dimensions that can be developed in terms of the fundamental dimensions.
Velocity, Acceleration, Force, Pressure, Density, Heat Capacity, Energy, Power, etc.
Important Note!
“Fundamental” or “Derived” – depending also on dimension/unit systems.
(ดูตาราง​ 1.1, AH)

6. Units Units : means of expressing dimensions Systems of Units
Length; feet, meters
Time; hours, seconds
Systems of Units
SI : Le Systeme Internationale d’Unites (International System)
AE : American Engineering
USCS : U.S. Conventional System
Metric systems : CGS (centimeters, grams, seconds)
English system
(ดูตาราง​ 1.2, ตาราง 1.3 และภาคผนวก 1, AH)

7. SI Prefixes (Remember!)
G, giga, 109
M, mega, 106
k, kilo, 103
h, hecto, 102
da, deka, 101
d, deci, 10-1
c, centi, 10-2
m, milli, 10-3
μ, micro, 10-6
n, nano, 10-9

8. Caution! camel’s hair brush :
camel’s – hair brush or camel’s hair – brush?
Written with confusion
ms – milliseconds or meter seconds?
cm2 – square centimeters or centi square meters?
Written without confusion
m.s or (m)(s)
(cm)2

9. Operations with Units Addition, Substraction, Equality
only they are the same
2 kg + 1 kg = 3 kg
5 kg + 3 J
10 kg + 5 g
Multiplication and Division
be canceled or merged if they are identical
m2/m -> m
(kg)(m)/(s)
m2/cm
Nonlinear Operations
sin, log, exp, …
for simplicity, transform or scale variables to be dimensionless before apply nonlinear operations
log (r m) = log r + log m
log (r m / R m) = log r + log m – log R – log m = log r – log R = log(r/R)

10. Conversion of Units and Conversion Factors
Many sources – web sites, mobile applications, CD, handbooks, etc. – find a very good one and keep for your academic life and career.
For conversion or calculation, be systematic in writing.
Prefer format :

11. Caution!
There are several “miles”, “pounds”, “gallon”, “oz”, and “barrel”.
U.S. frequent-flier mile (nautical mile) -> 1.85 km
U.S. mile -> 1.61 km
Ancient Italian mile -> 37 modern U.S. miles

12. Special Attention : Mass and Force
Newton’s Law
F = ma or F = Cma
F = force
C = constant or conversion factor, whose numerical
value and units depend on those selected for F,
m and a
m = mass
a = acceleration

13. Special Attention : Mass and Force
AE system
Make the numerical value of the force and the mass be essentially the same at the earth’s surface.
1 lbf : the unit of force when 1 lbm is accelerated at g ft/s2
gc is a conversion factor (to cancel the numerical value of g).

14. Special Attention : Mass and Force
1 kgf : the unit of force when 1 kgm is accelerated at g m/s2
gc is a conversion factor (to cancel the numerical value of g).

15. Special Attention : Mass and Force
SI system
1 Newton (N) : the unit of force when 1 kg is accelerated at 1 m/s2

16. Examples
(P3, DMH)
Determine the kinetic energy of one pound of fluid moving in a pipe at the speed of 3 feet per second.
Ans (ft)(lbf)

17. Examples (P4, DMH) Convert the following from AE to SI units:
4 lbm/ft to kg/m
1.00 lbm/(ft3)(s) to kg/(m3)(s)
Ans. (a) 5.96 kg/m; (b) 16.0 kg/(m3)(s)

18. Examples (P5, DMH) Convert 1.57x10-2 g/(cm)(s) to lbm/(ft)(s)
Ans. 1.06x10-3 lbm/(ft)(s)

19. Dimensional Consistency (Homogeneity)
Both terms must have the same unit as d.
0.021 must have the unit of time.
This cannot be correct.
The lefthand side has units of 1/x, but the righthand side has units of x2 (the product of ax).

20. Examples
(P1, DMH) An orifice meter is used to measure the rate of flow of a fluid in pipes. The flow rate is related to the pressure drop by the following equation where u = fluid velocity ΔP = pressure drop (force per unit area) ρ = density of the flowing fluid c = constant Ans. c is dimensionless.

21. Examples
(P2, DMH)
The thermal conductivity k of a liquid metal is predicted via the empirical equation
k = A exp (B/T)
where k is in J/(s)(m)(K) and A and B are constants. What are the units of A and B?
Ans. A has the same units as k; B has the units of T