Higher Tier, Chemistry-only: gas volumes at room temperature and pressure
導入済み| English | 意味 |
|---|---|
| room temperature and pressure/ruːm ˈtemprɪtʃə ænd ˈpreʃə/ | 室温・常圧 |
| molar gas volume/ˈməʊlə ɡæs ˈvɒljuːm/ | 気体のモル体積 |
What would explain this observation?
- Higher Tier: One mole of hydrogen and one mole of carbon dioxide occupy the same gas volume at the same temperature and pressure. Their different masses do not change that equal-amount volume rule.
Build the model
- At the specification’s room temperature and pressure 室温和大气压, 20 °C and 1 atmosphere, one mole of gas occupies 24 dm³.
- Calculate V=24n in dm³, or n=V/24.
- For a gas mass, first calculate n=m/M, then volume.
- Conversely, a gas volume gives amount and then mass using its molar mass.
- This fixed molar-volume value is tied to the stated conditions.
- molar gas volume 气体摩尔体积: The volume occupied by one mole of gas at specified conditions.
- room temperature and pressure: Here the specified reference conditions of 20 °C and 1 atmosphere.
When do balanced coefficients give gas-volume ratios?
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Equal moles of any gas occupy equal volumes only at the SAME temperature and pressure - so coefficient ratios become volume ratios only for gases under matched conditions. Solids and liquids have their own molar volumes.
Match each technical term to its precise meaning.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Equal gas amounts occupy equal volumes at identical conditions, so balanced coefficients give gaseous volume ratios.
- N₂(g) + 3H₂(g) → 2NH₃(g) gives ratio 1:3:2 for gas volumes measured at the same temperature and pressure.
- This ratio does not apply to a liquid or solid volume.
- A predicted product volume assumes sufficient reactants and the stated complete-conversion model; real equilibrium can reduce conversion.
In the lab: Convert cm³ to dm³ consistently and label every volume’s conditions. Do not use 22.4 dm³ per mol, a value associated with different reference conditions, in this RTP task. Use teacher-provided gas data or approved low-risk gas collection under supervision; do not propose making ammonia or hydrogen in an improvised apparatus. Water-vapour and collection losses can affect real measurements.
Which two habits make the investigation or model in this case more defensible?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: 4.4 g CO₂ with molar mass 44 $\dfrac{\text{g}}{\text{mol}}$ gives 0.100 mol, hence 2.40 dm³ at RTP.
- In the ammonia equation, 6.0 dm³ H₂ can theoretically react with 2.0 dm³ N₂ to form 4.0 dm³ NH₃ at identical conditions.
- There are four reactant gas volumes for two product volumes; total gas volume need not be conserved even though atoms and mass are.
Your turn: At RTP, find the volume of 8.8 g CO₂ using molar mass 44 $\dfrac{\text{g}}{\text{mol}}$ and 24 dm³ per mol.
At RTP, find the volume of 8.8 g CO₂ using molar mass 44 g per mol and 24 dm³ per mol.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
The result is 4.8 dm³. Known: 8.8 g CO2; molar mass 44 g per mol; 24 dm^3 per mol at RTP. Amount = 8.8/44 = 0.20 mol. Volume = 0.20 x 24 = 4.8 dm^3. The 24 dm^3 figure is valid only at room temperature and pressure.
Check the conclusion and its limits
- The number 24 is not a universal gas volume at every temperature and pressure.
- Coefficients concern gas volume only under matched conditions.
- Equal gas volumes can have different masses, and a reduction in total gas volume does not mean atoms disappeared.
Not true: Total gas volume is always conserved in a balanced chemical reaction. Atoms and mass are conserved, but gas volume is not: 3 volumes of hydrogen plus 1 of nitrogen give only 2 of ammonia. Volume follows the gas MOLE count, which the reaction can change.
- At the specification’s room temperature and pressure, 20 °C and 1 atmosphere, one mole of gas occupies 24 dm³.
- Equal gas amounts occupy equal volumes at identical conditions, so balanced coefficients give gaseous volume ratios.
- Watch for: the number 24 is not a universal gas volume at every temperature and pressure.
Total gas volume is always conserved in a balanced chemical reaction.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Atoms and mass are conserved, but gas volume is not: 3 volumes of hydrogen plus 1 of nitrogen give only 2 of ammonia. Volume follows the gas MOLE count, which the reaction can change.
The volume occupied by one mole of gas at specified conditions: write the technical term.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
molar gas volume means The volume occupied by one mole of gas at specified conditions.