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title: "A student determines the empirical formula of an unknown metal oxide, \\(\\text{M}_x\\text{O}_y\\), by heating a weighed sample of pure metal \\(\\text{M(s)}\\) in an open porcelain crucible to completely convert it to the solid oxide. Before the initial weighing of the empty crucible, an improperly adjusted, yellow burner flame deposited a thin layer of carbon soot, \\(\\text{C(s)}\\), onto the exterior of the crucible. The student recorded the mass of the sooty crucible, added the metal, recorded the combined mass, and then heated the crucible strongly with a clean, hot blue flame until the metal was fully oxidized and all the exterior soot had combusted to \\(\\text{CO}_2\\text{(g)}\\). Based on this experimental error, which of the following predicts the effect on the calculated \\(\\text{O}:\\text{M}\\) mole ratio in the metal oxide product, and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/123498/"
date_modified: "2026-09-28T11:59:57+00:00"
---

# A student determines the empirical formula of an unknown metal oxide, \(\text{M}_x\text{O}_y\), by heating a weighed sample of pure metal \(\text{M(s)}\) in an open porcelain crucible to completely convert it to the solid oxide. Before the initial weighing of the empty crucible, an improperly adjusted, yellow burner flame deposited a thin layer of carbon soot, \(\text{C(s)}\), onto the exterior of the crucible. The student recorded the mass of the sooty crucible, added the metal, recorded the combined mass, and then heated the crucible strongly with a clean, hot blue flame until the metal was fully oxidized and all the exterior soot had combusted to \(\text{CO}_2\text{(g)}\). Based on this experimental error, which of the following predicts the effect on the calculated \(\text{O}:\text{M}\) mole ratio in the metal oxide product, and provides the correct justification?

A student determines the empirical formula of an unknown metal oxide, \(\text{M}_x\text{O}_y\), by heating a weighed sample of pure metal \(\text{M(s)}\) in an open porcelain crucible to completely convert it to the solid oxide. Before the initial weighing of the empty crucible, an improperly adjusted, yellow burner flame deposited a thin layer of carbon soot, \(\text{C(s)}\), onto the exterior of the crucible. The student recorded the mass of the sooty crucible, added the metal, recorded the combined mass, and then heated the crucible strongly with a clean, hot blue flame until the metal was fully oxidized and all the exterior soot had combusted to \(\text{CO}_2\text{(g)}\). Based on this experimental error, which of the following predicts the effect on the calculated \(\text{O}:\text{M}\) mole ratio in the metal oxide product, and provides the correct justification?

- **A.** The calculated \(\text{O}:\text{M}\) mole ratio will be too low because the combustion of the exterior soot consumes atmospheric \(\text{O}_2\text{(g)}\), preventing the metal sample from reacting completely.
- **B.** The calculated \(\text{O}:\text{M}\) mole ratio will be too low because the escape of \(\text{CO}_2\text{(g)}\) decreases the final measured mass, causing the calculated mass of oxygen to be smaller than the actual mass.
- **C.** The calculated \(\text{O}:\text{M}\) mole ratio will be too high because the initial presence of soot increases the recorded mass of the empty crucible, causing the calculated mass of metal \(\text{M}\) to be an underestimate.
- **D.** The calculated \(\text{O}:\text{M}\) mole ratio will be too high because the soot reacts with oxygen to form solid metal carbonates that remain in the crucible, artificially increasing the final mass of product.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123498/*