The mole is a quantity of substance. The new prefix ‘guaca’ is defined suchthat one guacamole equals Avocado’s Number.

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—G. Byrne.

For much better or worse, there space a variety of unit systems that engineers have to compete with ~ above a constant basis.

The two equipment we will address most frequently are the following:

unit system

selected base units

SI (International device of Units)

\(\sim\), \(\sikg\), \(\siN\), \(\sis\)

United says customary

\(\sift\), \(\silb_f\), \(\silb_m\), \(\sis\)

What is a pound?¶

Some resources use the term pound to median pound massive (lbm or \(\silb_m\)) andothers usage it to mean pound force (lbf or \(\silb_f\)).This is analogous come the difference in between mass and weight, i m sorry are additionally commonly confused.

Weight is the pressure exerted ~ above a massive by the regional gravitational field,\(f = m \cdot a = m \cdot g\), wherein \(\sig\) is the acceleration the gravity.Thus, \(\silb_f\) = \(\silb_m\) \(\cdot\) \(\sig\).

What is a gmol?… a kgmol?… a lbmol?¶

First, what is a mole?

A mole is a certain number of molecules, atoms, electrons, etc.In the SI system, the mole has about \(\num6.022140d23\) particles.This is correctly defined as a gram mole, though SI units officiallydesignate this together a mole.

Alternatively, a \(\sikgmol\) (kilogram mole) is same to \(1000\)gram moles, and therefore can be believed of as having \(1000\)times \(\num6.022140d23\) particles.

A \(\silbmol\) (pound mole) has \(454\) time \(\num6.022140d23\)particles and also is thus larger than a \(\sigmol\).

Another way to look at the mole unit is together a unit offered to convert thenumber of moles to mass, using the molecular load (\(MW\)).

In summary

\(\sigmol\) = (mass in grams) / \(MW\)

\(\silbmol\) = (mass in pounds) / \(MW\)


mass in \(\sig\) = \(MW\) \(\cdot\) \(\sigmol\)

mass in \(\silb_m\) = \(MW\) \(\cdot\) \(\silbmol\)

Converting in between units¶

Converting devices is a very essential skill for CBEs.

It helps united state to

use a consistent collection of devices in calculations

transfer results into and out of various other unit systems of interest

assure the equations space formulated correctly

Your textbook, Introduction to chemistry Engineering: tools for Today and also Tomorrowhas tables of common conversion determinants (page xix of the 5th edition):


Perry’s chemical Engineers’ Handbook (highly recommended) and theCRC Handbook that Chemistry and also Physics have many more conversion factors.

There space different, equivalent, ways that you will certainly see systems written.

For instance, the devices for the heat transfer coefficient, \(h\),can it is in written plenty of ways:

\(\mathrmW \cdot m^-2 \cdot K^-1\)



\(\mathrmW/(m^2 K)\)

\(\mathrmW/(m^2 \cdot K)\)

\(\mathrmW m^-2 K^-1\)

\(\mathrmW/m^2 \cdot K\)

\(\frac\mathrmW\mathrmm^2 \cdot K\)


Convert \(\SI5W/m^2.\degree C\)to \(\siBtu/s.ft^2.\degree F\)

\<\SI5\frac\siW\sim^2.\degree C \cdot\left(\frac\SI3.412Btu/hr\SI1W\right)\left(\frac\SI1hr\SI3600s\right)\left(\frac\SI1m\SI3.28ft\right)^2\left(\frac\SI1\degree C\SI1.8\degree F\right)= \SI2.447d-4\frac\siBtu\sis.ft^2.\degree F\>

Exercise: Unit conversion

In their third most outstanding prank to date, CBE students totally drained Horsetooth reservoir.


As the water resource engineer in charge, it is your obligation to refill it. ☹

A pair of passionate interns working for girlfriend volunteer to walk to the store to choose up the required water in 1-liter bottles.

A 1-liter party of water is around \(\SI11inches\) tall.

See more: What Is Everyday Motion Usually Relative To, Speed And Velocity

If the compelled bottles to be placed end to end, just how long would certainly the ridge be?

In almost right terms, would the length be the street from…

the soil floor to the optimal of the Petronas pair Towers (\(\approx \SI450meters\))?

sea level to the optimal of mount Everest (\(\approx \SI8.9d3meters\))?

Fort Collins come Denver (\(\approx \SI100km\))?

the planet to the Moon (\(\approx \SI380d3km\))?

the earth to Mars (\(\approx \SI55d6km\) at your closest)?

the sun to Pluto (\(\approx \SI4.4d9km\) at your closest)?

Exercise: Unit switch for tradition units

In physics, the first radiation constant, \(c_1\),is approximately \(\SI3.741d-16W.m^2\),where \(\siW\) is watts ( \(\siJoules/s\) ), a unit that power.

Being a clever engineering student, friend have occurred a brand-new system ofunits that you find more intuitive. The pertinent units and also conversionfactors in your mechanism are as follows: