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Questions and Answers
How does anhydrous copper (II) sulfate change in the presence of water?
How does anhydrous copper (II) sulfate change in the presence of water?
It turns from white to blue.
What are the freezing and boiling points of pure water at atmospheric pressure?
What are the freezing and boiling points of pure water at atmospheric pressure?
Freezing point is 0°C and boiling point is 100°C.
What flame color indicates the presence of sodium ions ($Na^+$) during a flame test?
What flame color indicates the presence of sodium ions ($Na^+$) during a flame test?
Yellow
Why is sodium hydroxide used to test for the presence of metal ions?
Why is sodium hydroxide used to test for the presence of metal ions?
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What is the chemical equation for the reaction of anhydrous copper (II) sulfate with water?
What is the chemical equation for the reaction of anhydrous copper (II) sulfate with water?
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What is the flame color for lithium ions ($Li^+$) in a flame test?
What is the flame color for lithium ions ($Li^+$) in a flame test?
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Describe the change you would see when testing an impure water sample for its freezing point
Describe the change you would see when testing an impure water sample for its freezing point
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What precipitate forms when sodium hydroxide solution is added to a solution containing copper ions ($Cu^2+$)?
What precipitate forms when sodium hydroxide solution is added to a solution containing copper ions ($Cu^2+$)?
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What is the visible result when testing for carbon dioxide gas with limewater?
What is the visible result when testing for carbon dioxide gas with limewater?
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Describe the chemical reaction that occurs when hydrogen gas reacts with a flame.
Describe the chemical reaction that occurs when hydrogen gas reacts with a flame.
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How would you test for the presence of chlorine gas?
How would you test for the presence of chlorine gas?
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What observation indicates the presence of ammonia using universal indicator paper?
What observation indicates the presence of ammonia using universal indicator paper?
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What happens when you place a glowing splint into a tube containing oxygen gas?
What happens when you place a glowing splint into a tube containing oxygen gas?
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What reagent is added to the solution to test for the presence of iodide ions?
What reagent is added to the solution to test for the presence of iodide ions?
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Why is dilute nitric acid added to the solution before silver nitrate?
Why is dilute nitric acid added to the solution before silver nitrate?
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What indicates the presence of iodide ions in the solution?
What indicates the presence of iodide ions in the solution?
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Write the chemical equation for the reaction that occurs when silver nitrate is added to a solution containing iodide ions.
Write the chemical equation for the reaction that occurs when silver nitrate is added to a solution containing iodide ions.
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What are the physical states of the reactants and product in the given chemical equation?
What are the physical states of the reactants and product in the given chemical equation?
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What color precipitate indicates the presence of copper ions (Cu2+)?
What color precipitate indicates the presence of copper ions (Cu2+)?
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Write the chemical equation for the reaction between iron(III) ions (Fe3+) and sodium hydroxide (NaOH).
Write the chemical equation for the reaction between iron(III) ions (Fe3+) and sodium hydroxide (NaOH).
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Which ion results in the formation of a green precipitate when reacting with sodium hydroxide?
Which ion results in the formation of a green precipitate when reacting with sodium hydroxide?
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What gas is produced when ammonium salts react with sodium hydroxide?
What gas is produced when ammonium salts react with sodium hydroxide?
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How can you confirm the presence of carbonate ions (CO3^2-)?
How can you confirm the presence of carbonate ions (CO3^2-)?
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Describe the test for sulfates (SO4^2-).
Describe the test for sulfates (SO4^2-).
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Which reagent is added to a chloride solution to test for chloride ions?
Which reagent is added to a chloride solution to test for chloride ions?
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What is the chemical equation for the reaction between barium ions (Ba2+) and sulfate ions (SO4^2-)?
What is the chemical equation for the reaction between barium ions (Ba2+) and sulfate ions (SO4^2-)?
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What is the expected observation when bromide ions (Br-) are tested with silver nitrate solution?
What is the expected observation when bromide ions (Br-) are tested with silver nitrate solution?
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Write the equation for the reaction of ammonium chloride (NH4Cl) with sodium hydroxide (NaOH).
Write the equation for the reaction of ammonium chloride (NH4Cl) with sodium hydroxide (NaOH).
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Study Notes
Chemical Tests
- Testing for gases:
- Hydrogen gas: reacts with a flame producing a squeaky pop, $2H_2 + O_2 \longrightarrow 2H_2O$
- Oxygen: relights a glowing splint
- Carbon dioxide: turns limewater milky/chalky/cloudy, $CO_2(g) + Ca(OH)_2(aq) \longrightarrow CaCO_3(s) + H_2O(l)$
- Chlorine: bleaches (turns white) damp red litmus paper
- Ammonia: turns universal indicator paper/litmus paper blue
Testing for Water
- Test for presence of water using anhydrous copper (II) sulfate: water turns white anhydrous copper (II) sulfate blue, $CuSO_4(s) + 5H_2O(l) \rightleftharpoons CuSO_4.5H_2O(s)$
- Test for purity of water: pure water freezes at exactly 0°C and boils at exactly 100°C atmospheric pressure
Testing for Ions
- Flame test for metal ions (cations):
- Lithium (Li+): red flame
- Sodium (Na+): yellow flame
- Potassium (K+): lilac flame
- Calcium (Ca+2): orange-red flame
- Copper (Cu+2): blue-green flame
Testing for Specific Ions (Cations)
- Using sodium hydroxide solution:
- Copper (Cu2+): formation of a blue precipitate, Cu2+(aq) + 2NaOH(aq) -> Cu(OH)2(s) + 2Na+(aq)
- Iron (Fe3+): formation of an orange-brown precipitate, Fe3+(aq) + 3NaOH(aq) -> Fe(OH)3(s) + 3Na+(aq)
- Iron (Fe2+): formation of a green precipitate, Fe2+(aq) + 2NaOH(aq) -> Fe(OH)2(s) + 2Na+(aq)
- Ammonium (NH4+): formation of a colorless gas, NH4Cl(aq) + NaOH(aq) -> NaCl(aq) + NH3(g) + H2O(l)
Testing for Anions
- Carbonate (CO32-): formation of carbon dioxide gas, 2HCl(aq) + CaCO3(s) -> CaCl2(aq) + CO2(g) + H2O(l)
- Sulfates (SO42-): formation of a white precipitate of barium sulfate, Ba2+(aq) + SO42-(aq) -> BaSO4(s)
- Chloride (Cl-): formation of a white precipitate of silver chloride, Ag+(aq) + Cl-(aq) -> AgCl(s)
- Bromide (Br-): formation of a cream precipitate of silver bromide, Ag+(aq) + Br-(aq) -> AgBr(s)
- Iodide (I-): formation of a yellow precipitate of silver iodide, Ag+(aq) + I-(aq) → AgI(s)
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Description
Identify the chemical tests for different gases, including hydrogen, oxygen, and carbon dioxide. Learn the reactions and equations involved in these tests.
