# Difference between molecular mass and molar mass

• gracy
In summary, molecular mass of water is constant and molecular weight is an antiquated term that, back in the day, was used to describe what we now call molecular mass. Relative molecular mass with a specification of which mass standard 16O, old standard, or 12C, new.

#### gracy

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?

gracy said:
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.
gracy said:
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.
gracy said:
mass of one mole of water i.e 18 g
Yes.
gracy said:
Molecular mass of water is constant
Yes.

• gracy
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

Chestermiller said:
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?

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

• gracy
Bystander said:
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.

To Bystander
Why you have blocked me?You are my favorite.You have been very helpful to me.
Regards.

gracy said:
Why you have blocked me.
Huh?

To Bystander
Why have you blocked me?You are my favorite.You have been very helpful to me.
Regards.

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

Bystander said:
I haven't blocked anyone as far as I know.
Why I am not able to do conversation with you?I have asked this question,and one of members answered that you might have blocked me.

There are limits on number of conversations. Did have a couple old ones that I just cleared out. Try again.

Bystander said:
Try again.
I am still not able to start conversation with you.

## What is the difference between molecular mass and molar mass?

Molecular mass refers to the mass of a single molecule of a substance, while molar mass refers to the mass of one mole of a substance. One mole of a substance is equal to its molecular mass expressed in grams.

## How are molecular mass and molar mass calculated?

Molecular mass is calculated by adding the atomic masses of all the atoms present in a molecule. Molar mass is calculated by multiplying the atomic mass of each element by the number of atoms of that element in one molecule, and then adding all of these values together.

## Why is molar mass important in chemistry?

Molar mass is important in chemistry because it allows us to easily convert between the mass of a substance and the number of moles of that substance. This is essential for accurate measurements and calculations in chemical reactions.

## What is the unit of measurement for molecular mass and molar mass?

The unit of measurement for both molecular mass and molar mass is atomic mass units (amu) or grams per mole (g/mol).

## Can molecular mass and molar mass be used interchangeably?

No, molecular mass and molar mass cannot be used interchangeably. While they are related, they refer to different quantities and have different units of measurement. Molecular mass is specific to a single molecule, while molar mass is specific to a mole of a substance.