Review: Conserving atoms and predicting reaction amounts
Use balanced symbolic models, mass boundaries, and stoichiometric ratios.
Bring the unit skills together
Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.
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Use the skills in a new task
Audit a fictional paper reaction report for N₂ + 3 H₂ → 2 NH₃. Its packet has 5 N₂ and 9 H₂ molecules; it claims 10 NH₃ and no leftovers. Correct it using set counts and atom conservation. Separately, scale the balanced equation for 2 mol N₂ with sufficient H₂. A mass ledger starts at 90 g and ends at 86 g inside an open boundary, with no input; explain the difference.
Work on paper or in your own document. Explain the choices you made.
- Check balanced per-set counts of 2 N and 6 H atoms.
- Find H₂ limits the packet to three sets, making 6 NH₃ and leaving 2 N₂.
- For 2 mol N₂, state 6 mol H₂ required and 4 mol NH₃ produced.
- Account for 4 g exiting the open mass boundary without matter destruction.
Compare with a model response
The equation has 2 N and 6 H per set. Nine H₂ allow only three sets, so the packet makes 6 NH₃ and leaves 2 N₂. Atom totals remain 10 N and 18 H: product has 6 N and 18 H, leftovers add 4 N. For 2 mol N₂ the completion model needs 6 mol H₂ and yields 4 mol NH₃. The separate open ledger has 90 − 86 = 4 g crossing out, rather than matter disappearing.
A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.