Understanding g mol in Unit Operations Course

[conSCIous]

I am currently taking a Unit Operations course. The book and the instructor both refer to a unit, g mol (gram mol). The book defines molarity as 1 (g mol)/Liter. I am familiar with molarity but always in the past it was defined as mol/Liter. I do not understand what this unit is supposed to be. Mass? mols? Can someone clear this up for me?

The text I am using is Transport Processes and Separation Process Principles, 4th edition, Christie Geankopolis.

thanks

 

[Bystander]

"gmol" --- "relative" molecular mass times grams; compare to the kgmol, lbmol, tonmol (English or metric --- going to be different). The chemists got here first, and a "mole" (mol) is understood to be a g-mol --- had chemists been raised in religious awe of the English units system, we might have a convention in which the unspecified "mol" would be understood to be the dram, scruple, poise, oz., grain, or some other irrational mass unit times molecular mass (weight).

 

[Gokul43201]

To summarize (at the cost of sounding repetitive) : "g mol" is the same as "mol", as per accepted convention.

 

[dextercioby]

"Mol"is in perfect connection with "gram" and "Kilomol" with "Kilogram".Par éxample
18 grams of water =1 mol
18 Kilograms of water=1 Kilomol

Daniel.

 

[DB]

Even though this isn't exactly related I think it might help you understand

C=\frac{n}{V}

where C is the molar concentration in moles per liter (mol/L)
V is the volume in Liters
n is the number of moles of solute

I'm doing this type of stuff now, so here's and example:
1 mole of H2SO4 = 98 g
What is the volume of a solution whose concentration is 0.2 mol/L if it contains 49 grams of sulphuric acid.

So in looking for the volume you have
V=\frac{n}{C}

but n must be in moles not grams so

\frac{1 \\ mole}{98 \\ g}=\frac{x \\ mole}{49 \\ g}
Cross multiply and you get 0.5 mole is equal to 49 grams of sulphuric acid. (though its just haf and half )

Now when you use the formula you always want your units to cancel out and in this case be left with L.

V=\frac{0.5 \\ mol}{\frac{0.2 \\ mol}{L}}

mol cancels and you're left with L.

V=\frac{0.5}{0.2}=2.5 Liters

So mole and grams are interchangible just with a little math and sometimes not even, for example 39 grams of Potasium (atomic mass) is equal to 1 mol of atoms, and so on.
Maybe it helped.