Science · Honors Chemistry
Chapter 1: Quantitative Foundations
A ratio is not a count.
Formaldehyde, a sharp-smelling gas, acetic acid, the sour part of vinegar, and glucose, a sugar, each analyze as 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass.
If the composition is identical, what further measurement tells them apart?
Make your guess to turn the page.
Still to come: 10 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students take an empirical formula as the identity of a compound. The book runs a combustion analysis to CH₂O and then shows three compounds sharing it, told apart only by molar mass. Ask: if you doubled every number in a ratio, would the percentages change? The idea to reach is that ratio, count and structure are three different questions.
The history, and how sure the figures are — The silver oxide percentages are rounded from the figures usually quoted for Wöhler’s cyanate and Liebig’s fulminate analyses. Liebig’s Kaliapparat dates from 1831; his method burned the sample over hot copper oxide rather than in a stream of oxygen. Proust and Berthollet argued over definite proportions from about 1799 to 1807.