Gas identification: chlorine bleaches damp litmus
| English | 中文 | Pinyin |
|---|---|---|
| damp litmus | 湿润石蕊试纸 | shī rùn shí ruǐ shì zhǐ |
| bleaching | 漂白 | piǎo bái |
What would explain this observation?
- Chloride ions in sodium chloride do not behave like chlorine gas. An identification answer must specify the tested species rather than relying on the shared word chlorine.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- The specified chlorine test uses damp litmus 湿润石蕊试纸 paper placed into the gas. Chlorine bleaches the paper so it turns white. The paper must be damp; dry litmus is not the stated method. Blue litmus may first turn red before bleaching 漂白, but the identifying final observation is bleaching white. Describe both the damp paper and the observed bleaching, rather than reporting an acid colour change alone.
- bleaching: Removal of the indicator colour so damp litmus becomes white in the stated chlorine test; damp litmus: Litmus paper moistened for the specified chlorine gas test.
Which observation is the specified positive chlorine result?
Chlorine is Cl₂, a molecular element, while chloride is Cl⁻, a negative ion in compounds and solutions. Their tests are different: gas bleaching identifies chlorine under suitable conditions, whereas acidified silver nitrate precipitates chloride ions. Pale green gas appearance can support the description but does not justify smelling a sample. Not every substance containing chlorine atoms releases chlorine gas or bleaches paper in the same way.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Chlorine is Cl₂, a molecular element, while chloride is Cl⁻, a negative ion in compounds and solutions. Their tests are different: gas bleaching identifies chlorine under suitable conditions, whereas acidified silver nitrate precipitates chloride ions. Pale green gas appearance can support the description but does not justify smelling a sample. Not every substance containing chlorine atoms releases chlorine gas or bleaches paper in the same way.
- Chlorine is harmful to breathe. Actual testing uses only teacher-approved small quantities, suitable ventilation/containment and controlled handling under the current school risk assessment. Never sniff the gas, generate it from improvised cleaning products or independently repeat an electrolysis setup to obtain it. Students can interpret source observations if direct exposure is unsuitable; the teacher records what actual practical experience and demonstration evidence were provided.
Which two habits make the investigation or model in this case more defensible?
Chlorine is harmful to breathe. Actual testing uses only teacher-approved small quantities, suitable ventilation/containment and controlled handling under the current school risk assessment. Never sniff the gas, generate it from improvised cleaning products or independently repeat an electrolysis setup to obtain it. Students can interpret source observations if direct exposure is unsuitable; the teacher records what actual practical experience and demonstration evidence were provided.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a supplied qualitative record has five damp papers becoming white and three tests reported inconclusive. There are eight records total, and clear-bleaching proportion=5/8×100=62.5%. That proportion describes the observation dataset, not the chlorine concentration or the method’s universal accuracy. An inconclusive result remains distinct from an observed non-bleaching result.
Six of eight supplied damp-litmus records show clear bleaching. Calculate the percentage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Six of eight supplied damp-litmus records show clear bleaching. Calculate the percentage.
The result is 75 %. Known: a supplied qualitative record has five damp papers becoming white and three tests reported inconclusive. There are eight records total, and clear-bleaching proportion=5/8×100=62.5%. That proportion describes the observation dataset, not the chlorine concentration or the method’s universal accuracy. An inconclusive result remains distinct from an observed non-bleaching result.
Check the conclusion and its limits
- Do not confuse bleaching with the simple red/blue indicator response, write dry litmus as the required reagent or use a smell test. Chloride precipitation is a separate solution-ion test. A written explanation does not authorise chlorine handling or certify a supervised task was performed. The gas-test objective applies on both tiers.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Chloride ions and chlorine gas must have the same identification test. This claim is false: Do not confuse bleaching with the simple red/blue indicator response, write dry litmus as the required reagent or use a smell test. Chloride precipitation is a separate solution-ion test. A written explanation does not authorise chlorine handling or certify a supervised task was performed. The gas-test objective applies on both tiers.
Gas identification: chlorine bleaches damp litmus: Chlorine is Cl₂, a molecular element, while chloride is Cl⁻, a negative ion in compounds and solutions. Their tests are different: gas bleaching identifies chlorine under suitable conditions, whereas acidified silver nitrate precipitates chloride ions. Pale green gas appearance can support the description but does not justify smelling a sample. Not every substance containing chlorine atoms releases chlorine gas or bleaches paper in the same way.
Chloride ions and chlorine gas must have the same identification test.
Do not confuse bleaching with the simple red/blue indicator response, write dry litmus as the required reagent or use a smell test. Chloride precipitation is a separate solution-ion test. A written explanation does not authorise chlorine handling or certify a supervised task was performed. The gas-test objective applies on both tiers.
Removal of the indicator colour so damp litmus becomes white in the stated chlorine test: write the technical term.
bleaching means Removal of the indicator colour so damp litmus becomes white in the stated chlorine test.