{"id": "card_n_18b53f98f008", "kind": "note", "title": "The mole — counting the uncountable", "body": "A mole is 6.02214076×10²³ things — exact since the 2019 SI redefinition — the bridge\nfrom atoms you cannot see to grams you can weigh. The molar mass is just the atomic weights\nadded up, sealed: water 18.015, CO2 44.009, table salt 58.443 g/mol (https://narrowhighway.com/s/54db514fbdd51c90cad455bc773f8152da3b3eb6a53119da6ddb670c9464e23b). That is why a\nrecipe in atoms becomes a recipe on a scale: 18 grams of water IS Avogadro's number of\nmolecules. The count is exact and the arithmetic seals; the atomic weights themselves are\nmeasured nature (isotope abundances), honestly not derived.", "source": {"label": "Concordance assay — 2026-07-09", "url": "https://narrowhighway.com/s/54db514fbdd51c90cad455bc773f8152da3b3eb6a53119da6ddb670c9464e23b", "ref": "chemistry", "authority_tier": "engine_derived"}, "shelf": "science", "box": "chemistry", "bands": ["mole", "avogadro", "molar mass", "6.022e23", "atomic weight", "stoichiometry", "grams"], "connections": [], "author": "engine", "created_at": "2026-07-10T01:59:02.989940+00:00", "updated_at": "2026-07-10T01:59:02.989940+00:00", "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "surface": "secular", "metrics": {"paperclips_count": 0, "helpful_count": 0, "not_helpful_count": 0, "cite_count": 0, "walks_through_count": 0, "flagged_count": 0}, "source_hash": "7d884a605d49c0dbb2b59820598e560d2c35b4407c94d8c0f422faf9be3bace8"}