Chemistry 11–12 · Year 12
Nitrogen dioxide and dinitrogen tetroxide in sealed tubes: the effect of temperature and pressure on a gas equilibrium
Module 5: Equilibrium and Acid Reactions
Teacher-led demonstration
A teacher carries out this activity as a demonstration. Its materials, steps, variables, misconceptions and sources are not published on the open web, and neither is any result, control or note that states a number or an amount: tutors and administrators read them on the learning platform, with the safety card first. The idea, the hazards and the curriculum references are below.
Open the procedure on the learning platform (tutor or administrator sign-in)
School laboratory, not for home
In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.
The idea
A brown gas in equilibrium with its colourless dimer pales when cooled and darkens when warmed, and compression shifts it towards the dimer, so the compressed gas ends less dark than its higher concentration alone would make it: temperature and pressure both shift a gas-phase equilibrium.
Safety card
Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
Hazards
- nitrogen dioxide is highly toxic and corrosive to the lungs
- sealed glass tubes can crack if heated above the stated limit
- lead(II) nitrate decomposition (if used) releases nitrogen dioxide and oxygen and forms toxic lead oxide
Controls
At least one of them states a number or an amount, which may be part of the method, so the controls are shown with the method to tutors and administrators on the learning platform.
Note
It states a number or an amount, which may be part of the method, so it is shown with the method to tutors and administrators on the learning platform.
What you should see
It states a number or an amount, which may be part of the method, so it is shown with the method to tutors and administrators on the learning platform.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document)CH12-12CH11/12-5CH11/12-6CH11/12-7
- Chemistry 11-12 Syllabus (2025), NESA; implemented from 2028, not yet taughtCH-12-01CH-12WS-05CH-12WS-06
- Australian Curriculum v9No Australian Curriculum v9 code is listed.