# Difference between molecular mass and molar mass

Molecular mass of water is constant i.e mass of one mole of water i.e 18 g
Molar mass is the mass of a substance depending on how many moles of substance is taken into consideration.
Ex.
A mole of H2O: 18 g
Two moles of H2O: 36 g
Three moles of H2O: 54g
and so on.
Right?
And molecular mass and molecular weight are same ,right?

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molecular mass and molecular weight are same ,right?
Not really. Mass is mass. Weight is mass times acceleration. When you're in the lab "weighing" materials you are performing that operation in the earth's gravitational field and the acceleration is 9.8 m/s2 and usually ignored in scale or balance calibrations.
Molar mass is the mass of a substance depending on how many moles of substance is taken into consideration.
No. "Molar mass" is the mass of ONE mole. Chemists usually use the "gram mole" which is molecular mass times one gram.
mass of one mole of water i.e 18 g
Yes.
Molecular mass of water is constant
Yes.

• gracy
Chestermiller
Mentor
Molecular weight is an antiquated term that, back in the day, was used to describe what we now call molecular mass. (I still call it molecular weight)

Chet

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what we now call molecular mass
And, to be strictly correct, "relative molecular mass" with a specification of which mass standard 16O, old standard, or 12C, new.

And what about difference between molecular mass and molar mass?

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Chemists usually use the "gram mole" which is molecular mass times one gram.

• gracy
DrDu
Chemists usually use the "gram mole" which is molecular mass times one gram.
I must be an unusual chemist, then :-)
Whatever a "gram mole" may be, it is certainly not the molecular mass times one gram.
Rather the molecular mass, i.e. the mass of a single molecule, is usually specified in units of "Daltons" where 1 u = 1 g/mol /Na =1.660 538 921(73)×10−27 kg.
This has the effect that the molar mass, i.e. mass of one mole of these molecules has the same numerical value in units of g/mol as has the molecular mass in units of Daltons.
This has the confusing effect for adepts that chemists often don't differentiate between molecular and molar mass.
Also, they often speak of "molecular weight" instead of molecular mass, a relic from the pre-history of science, when people still did not clearly differentiate between mass and weight. E.g. Berzelius had a wooden sign over the door of his lab, saying:
"God has ordered everything according to its number, measure and weight".
But till then, almost 200 years have passed.

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Why you have blocked me.
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Why you have blocked me?
I haven't blocked anyone as far as I know.

I haven't blocked anyone as far as I know.
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