molar mass
Let an agent compute and state molar masses with units and sources, and use them correctly in conversions between mass and amount.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent compute and state molar masses with units and sources, and use them correctly in conversions between mass and amount.
The mass of one mole of a substance, expressed in grams per mole, equal numerically to the relative molecular or formula mass.
What it is for: Converting between mass and amount of substance in chemistry and industry.
It can be calculate it from a formula; look it up in data sources; use it to convert grams to moles; characterise polymers by molar mass distribution.
Distinguishing features
Mass per amount of substance
Depends on isotopic composition
Polymers have distributions, not single values
Different from molecular mass in daltons, though numerically equal
What it looks like
A number with g/mol on data sheets and labels.
Physical character
water: 18.015 g/mol
carbon dioxide: 44.009 g/mol
How it is recognised
Values in g/mol
Formula weight in older texts
Distributions (Mn, Mw) for polymers
Related models
is a property of - substance
relates - conversion
is a kind of - molar quantity
is used in - stoichiometry
In practice
Families and kinds
molar mass of compounds
formula weight for ionic compounds
molar mass distributions for polymers
molar mass of solvents
Identifiers
unit g/mol or kg/mol SI coherent unit is kg/mol
Standards and regulation
IUPAC standard atomic weights
SI Brochure on the mole
Failure modes and hazards
Using wrong formula or hydrate form
Unit errors
Rounding errors in precise work
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Value The molar mass.
Value and source.
Computation
From formula.
Computation
Calculation.
- What is the molar mass computed from the formula? measurement
- Which atomic weights were used? provenance
Form
Hydrates and salts.
Form
Chemical form.
- Which form of the substance, such as a hydrate? boundary
- Does it change the value? measurement
Use Conversions.
Conversions are routine but error-prone.
Conversion
Grams and moles.
Conversion
Conversion.
- How many moles are in this mass? measurement
- Are units consistent? boundary
Stoichiometry
Reactions.
Stoichiometry
Stoichiometric use.
- How is it used in the reaction calculation? definition
- What is the limiting reagent? measurement
Polymers Distributions.
Polymers have distributions.
Averages
Mn and Mw.
Averages
Average molar masses.
- What are Mn and Mw, and the dispersity? measurement
- By which method? provenance
Effect
Properties.
Effect
Effect on properties.
- How does molar mass affect the material properties? definition
- What range is specified? measurement
Quality Precision and sources.
Precision depends on use.
Precision
Significant figures.
Precision
Needed precision.
- How precise must the value be for this use? boundary
- Which rounding is appropriate? measurement
Sources
Reference data.
Sources
Reference sources.
- Which reference source gives the value? provenance
- Is it current? provenance
What the second pass must settle
- Should molar masses be stored on compound entries?
- How should isotopic variation be recorded?
- How should polymer distributions be represented?