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Questions and Answers
What is the main purpose of a reagent in qualitative analysis?
What is the difference between a positive test and a negative test?
What is the purpose of acidifying the solution in the anion tests?
What is the result of the chloride ion test?
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How many anion tests are performed in the experiment?
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What is the term for the change that occurs when a chemical reaction takes place?
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What is the result of the reaction between AgNO3 and NaCl?
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What is the purpose of adding 6M HCl to the solution in the sulfate ion test?
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Which reagent is used to test for the presence of nitrate ions?
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What is the observation when carbonate ions are present in the solution?
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What is the purpose of heating the solution in the phosphate ion test?
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What is the formula of the compound formed when BaCl2 reacts with Na2SO4?
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Study Notes
Objectives
- Learn to identify anions from their typical chemical reactions
- Learn to represent a chemical reaction as a net ionic equation
Changes in Chemical Reactions
- Formation or disappearance of:
- Colour
- Solid (precipitate)
- Gas
- Light
- Heat
- Change in instrument readings
Qualitative Analysis
- Reagent: a chemical substance that reacts selectively with one ion in the unknown to produce a change
- Two types of tests:
- Positive test: substance (anion or cation) is present in the unknown
- Negative test: substance (anion or cation) is absent or present in low concentration
Anion Tests
- Five anion tests:
- Chloride ion test (Cl-)
- Sulfate ion test (SO42-)
- Nitrate ion test (NO3-)
- Carbonate ion test (CO32-)
- Phosphate ion test (PO43-)
Anion Tests Reactions
- Chloride ion test: AgNO3 + NaCl → AgCl (white ppt) + NaNO3 (acidified with 6M HNO3)
- Sulfate ion test: BaCl2 + Na2SO4 → BaSO4 (white ppt) + 2NaCl (acidified with 6M HCl)
- Nitrate ion test: 8FeSO4 + 2NaNO3 + 4H2SO4 → [FeNO]SO4 (brown ring) + 3Fe2(SO4)3 + Na2SO4 + 4H2O (acidified with 6M H2SO4)
- Carbonate ion test: Na2CO3 + 2HCl → 2NaCl + H2O + CO2 (gas) (using 6M HCl)
- Phosphate ion test: Na3PO4 + 12(NH4)2MoO4 + 24HNO3 → (NH4)3[PO4(MoO3)12] (yellow ppt) + 3NaNO3 + 21NH4NO3 + 12H2O (heated using water bath)
Net Ionic Equation
- Chloride ion test: Ag+ + Cl- → AgCl (ppt)
- Formula: Molecular equation → Total ionic equation → Net ionic equation
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Description
This quiz covers the identification of anions from their chemical reactions and representation of chemical reactions as net ionic equations. It also includes changes observed in chemical reactions, such as formation or disappearance of color, solid, gas, light, heat, and changes in instrument readings. Learn how to analyze anions using reagents and chemical reactions.
