1,000,000 Question Thread :D

[kenhung123]

I don't understand this statement:
The molar mass (M) is found by taking the atomic, molecular or formula mass and expressing it in grams. For example, one mole of CO2 gas has a mass of 44g mole^-1.

[m@tty]

The relative atomic mass of Carbon was set at 12, there is no unit for RAM, then the mole was found so that one mole of Carbon-12 weighed 12 grams, hence all RAM can be expressed in grams as the weight which comprises one mole.

[kenhung123]

What is it saying here: The molar mass (M) is found by taking the atomic, molecular or formula mass and expressing it in grams.

[monokekie]

 The mass in grams of one mole of substance is called molar mass.

firstly, you could find CO2's molar mass through the use of atomic masses. atomic mass is the sum of the number of protons and neutrons found in the nucleus of an atom.You could find them on the periodic table e.g, carbon=12, Hydrogen=1, etc
so,atomic mass of one carbon =12, and atomic of one oxygen =16,
=> in carbon dioxide, there are one carbon and two oxygens, 12+16+16= 44 g, i.e, the molar mass of CO2

can you follow me?

[kenhung123]

Yep

[monokekie]

secondly, the molecular mass is often deemed as a synonym to molar mass, the major difference is that the unit of molecular mass is in "amu- atomic mass unit" while molar mass is in grams.

note: this would do for the VCE standard as their difference is actually above the scope of our course.

"Molecular mass differs from more common measurements of the mass of chemicals, such as molar mass, by taking into account the isotopic composition of a molecule rather than the average isotopic distribution of many molecules. As a result, molecular mass is a more precise number than molar mass; however it is more accurate to use molar mass on bulk samples. This means that molar mass is appropriate most of the time except when dealing with single molecules." - wikipedia


do you get this part?

[kenhung123]

Oh ok and formula and atomic mass is same

[monokekie]

you need to understand emperical formula to understand formula weight..
formula mass doesn't necessary equal to atomic mass..

[kenhung123]

molecular mass and formula mass (they are same?)is like a molecule composition right? Like H2O 2 H and 1 O Atomic mass is like 1 atom such as H O N

[kenhung123]

can someone tell me whether molecular and formula mass are the same or not? E.g. CO2

[Ilovemathsmeth]

Formula mass is used for ionic substances; molecular for covalent substances like CO2.

[kenhung123]

Formula mass is used for ionic substances; molecular for covalent substances like CO2.

Oh ok such as NaCl (formula) CO2 (molecular)?

I also want to ask is it important to know conversions in chemistry? Such as 1m^3=1000 000mL?

[Ilovemathsmeth]

Hmm I think you need to know them, especially miligram and microgram, they sometimes come up on exams...

[kenhung123]

Hmm I think you need to know them, especially miligram and microgram, they sometimes come up on exams...

Ahh, I find them confusing because sometimes I think something can be converted into another when it can't. Are you referring to conversion like mg>g and ug>g? Because I am worried about converting in 1 unit to another.

[m@tty]

You definitely need to know how to convert units. They could easily have a question which requires you to do so.