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Questions and Answers
What color is the residue when a zinc salt is heated and then cooled?
What color is the residue when a zinc salt is heated and then cooled?
Which radical produces carbon dioxide ($CO_2$) when heated?
Which radical produces carbon dioxide ($CO_2$) when heated?
What color is the residue when a cadmium salt is heated?
What color is the residue when a cadmium salt is heated?
In a charcoal cavity test, what type of flame is used?
In a charcoal cavity test, what type of flame is used?
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Why should excess cobalt nitrate be avoided in the cobalt nitrate test?
Why should excess cobalt nitrate be avoided in the cobalt nitrate test?
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Why does magnesium not impart any color in a flame test?
Why does magnesium not impart any color in a flame test?
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What is the purpose of using concentrated hydrochloric acid (HCl) when preparing a salt for a flame test?
What is the purpose of using concentrated hydrochloric acid (HCl) when preparing a salt for a flame test?
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What does the blue glass do in the flame test?
What does the blue glass do in the flame test?
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Why is platinum wire preferred over other metals for flame tests?
Why is platinum wire preferred over other metals for flame tests?
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Why should using a glass rod be avoided for flame tests instead of platinum?
Why should using a glass rod be avoided for flame tests instead of platinum?
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Why do barium salts not impart color to a flame immediately?
Why do barium salts not impart color to a flame immediately?
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Why is it recommended to avoid using platinum wire when testing lead salts?
Why is it recommended to avoid using platinum wire when testing lead salts?
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In the borax bead test, why should only a small amount of salt be used?
In the borax bead test, why should only a small amount of salt be used?
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Why is the borax bead test ineffective for white salts?
Why is the borax bead test ineffective for white salts?
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Why is dilute sulfuric acid (H2SO4) preferred over dilute hydrochloric acid (HCl) for testing acid radicals?
Why is dilute sulfuric acid (H2SO4) preferred over dilute hydrochloric acid (HCl) for testing acid radicals?
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What is the purpose of using an acidified potassium dichromate (K2Cr2O7) solution to differentiate between CO2 and SO2 gases?
What is the purpose of using an acidified potassium dichromate (K2Cr2O7) solution to differentiate between CO2 and SO2 gases?
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How can you distinguish between NO2 and Br2, both of which are brown gases?
How can you distinguish between NO2 and Br2, both of which are brown gases?
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What is the observation when CO2 gas is passed through lime water?
What is the observation when CO2 gas is passed through lime water?
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What happens when excess CO2 is passed through lime water?
What happens when excess CO2 is passed through lime water?
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What is the chemical formula for Sodium nitroprusside?
What is the chemical formula for Sodium nitroprusside?
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How can you test for the presence of sulphide ions in a sample?
How can you test for the presence of sulphide ions in a sample?
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Besides CO2, which other gas can turn lime water milky?
Besides CO2, which other gas can turn lime water milky?
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In the chromyl chloride test, what is the color of the vapor formed when a mixture is heated with concentrated H2SO4 and solid K2Cr2O7?
In the chromyl chloride test, what is the color of the vapor formed when a mixture is heated with concentrated H2SO4 and solid K2Cr2O7?
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What is the role of the paper pellet in the reaction of a nitrate with concentrated H2SO4?
What is the role of the paper pellet in the reaction of a nitrate with concentrated H2SO4?
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In the carbon disulfide test for bromide or iodide, what color appears when chlorine displaces bromine or iodine and dissolves in CS2?
In the carbon disulfide test for bromide or iodide, what color appears when chlorine displaces bromine or iodine and dissolves in CS2?
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Why do bromides and iodides NOT respond to the chromyl chloride test?
Why do bromides and iodides NOT respond to the chromyl chloride test?
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What is the principle behind the brown ring test for nitrates?
What is the principle behind the brown ring test for nitrates?
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Why is acetic acid added when testing for sulphides with lead acetate?
Why is acetic acid added when testing for sulphides with lead acetate?
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What role does the match stick play in the match stick test for sulfates?
What role does the match stick play in the match stick test for sulfates?
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Why does iodine give a blue color with starch solution?
Why does iodine give a blue color with starch solution?
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Why is the original solution (O.S.) not prepared using concentrated HNO3?
Why is the original solution (O.S.) not prepared using concentrated HNO3?
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Why is it necessary to add dilute HCl before testing for group II basic radicals?
Why is it necessary to add dilute HCl before testing for group II basic radicals?
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What role does $KMnO_4$ play in a titration where it is used?
What role does $KMnO_4$ play in a titration where it is used?
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Why is Mohr's salt preferred over ferrous sulfate as a primary standard in volumetric analysis?
Why is Mohr's salt preferred over ferrous sulfate as a primary standard in volumetric analysis?
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What is the role of concentrated sulfuric acid when preparing a standard solution of Mohr's salt?
What is the role of concentrated sulfuric acid when preparing a standard solution of Mohr's salt?
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What causes the formation of a brown precipitate during a $KMnO_4$ titration?
What causes the formation of a brown precipitate during a $KMnO_4$ titration?
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Why is it recommended to heat an oxalic acid solution to approximately 60-70C before titrating with $KMnO_4$?
Why is it recommended to heat an oxalic acid solution to approximately 60-70C before titrating with $KMnO_4$?
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Why is ammonium sulphate unsuitable for use in group III precipitation?
Why is ammonium sulphate unsuitable for use in group III precipitation?
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Which of the following is a cation that is not derived from a metal?
Which of the following is a cation that is not derived from a metal?
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A solution with a known strength is referred to as what type of solution?
A solution with a known strength is referred to as what type of solution?
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How is the equivalent mass of $KMnO_4$ determined when it functions as an oxidizing agent in an acidic medium?
How is the equivalent mass of $KMnO_4$ determined when it functions as an oxidizing agent in an acidic medium?
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What is the primary difference between molality and molarity?
What is the primary difference between molality and molarity?
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If a $0.10 M$ $KMnO_4$ solution is used in an acidic medium, what is its Normality?
If a $0.10 M$ $KMnO_4$ solution is used in an acidic medium, what is its Normality?
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What volume of 10M HCl is required to create 1L of 1M HCl?
What volume of 10M HCl is required to create 1L of 1M HCl?
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What is a rider used for in a chemical balance?
What is a rider used for in a chemical balance?
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Study Notes
Qualitative Analysis
- Qualitative analysis involves methods for identifying the components of a compound.
- A radical is an atom or group of atoms that carries a charge and acts as a single unit in reactions.
- Basic radicals have a positive charge, while acidic radicals have a negative charge.
- Inorganic salts have electrovalent bonds.
- Inorganic salts ionize in water due to water's high dielectric constant, weakening the forces holding the ions together.
- Ferrous salts are typically light green, while ferric salts are usually brown.
- Nickel salts are often bluish-green or green.
- Manganese salts are typically light pink or flesh-colored.
- Salts containing lead may turn black over time due to the formation of lead sulfide from atmospheric H₂S.
- Certain salts produce crackling sounds when heated (e.g., lead nitrate, barium nitrate, potassium bromide, sodium chloride).
- Sublimation is a process where a substance changes directly into a gas without melting.
- Preliminary tests can provide useful information about specific ions in a salt, such as sodium indicated by a golden yellow flame test.
- Dry heating tests can reveal information about certain components.
- A white residue from heating a zinc salt turns yellow when hot and white when cool.
- A hot cadmium salt residue appears brown, becoming brown when cooled.
- Absence of certain colors in a dry heating test can indicate the absence of specific radicals.
- Charcoal cavity tests involve heating salts mixed with sodium carbonate in a reducing flame, often revealing residue or metal beads indicating specific radicals.
- A reducing flame in a cavity test is obtained by adjusting the air intake on a Bunsen burner
Flame Test
- A flame test involves observing the coloration imparted to a flame by a substance to aid in identification.
- Magnesium does not impart any color to the flame because the flame's energy is insufficient to excite electrons to higher energy levels.
- The blue glass in flame tests is used to absorb unwanted colored light, allowing for clear identification of other colors.
- Solutions for flame tests are prepared by introducing concentrated acids (specifically HCl) to samples.
- Platinum wire is frequently used in flame tests due to its inertness (avoiding interference from the wire's makeup).
- Salts, specifically their metal components, are the part that impart color to the flame.
- Excess cobalt nitrate should be avoided to prevent a masking of other colors.
- The blue glass in flame tests is used to filter out unwanted light for clearer identification.
Other Tests
- Nessler's Reagent (K₂[HgI₄]) is a reagent used in chemical tests.
- Concentrated H₂SO₄ is a reagent used in some tests of acid radicals.
- Sodium carbonate extract is a solution prepared by combining a sample with sodium carbonate and water, followed by boiling and filtration.
- The distinction between CO₂ and SO₂ can be determined using acidified potassium dichromate (K₂Cr₂O₇).
- The presence of carbonate can be tested by reacting the unknown substance with a dilute acid, resulting in the liberation of carbon dioxide.
- Limewater is a calcium hydroxide solution (Ca(OH)₂) used to detect carbon dioxide gas.
- Sulfides can be identified by reacting the sample with a dilute H₂SO₄ solution.
- An indicator is needed to discern the endpoint of acid-base and other titrations.
Titration
- A standard solution is a substance with a known concentration used in titrations.
- A normal solution contains one equivalent weight of solute per liter.
- KMnO₄'s equivalent weight in acidic solutions is one-fifth its molecular weight.
- Sodium hydroxide is not typically a primary standard.
- Molality and molarity are distinct concentration measures.
- The maximum weight on a chemical balance is often 100g.
- A rider is a small mass used to balance weights below 10 mg.
- Titration involves the reaction between a known amount of solute and a known volume of another substance to quantitatively measure the unknown's concentration.
- An indicator changes color at the endpoint of a titration.
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Description
Test your knowledge on qualitative analysis, including the identification of components in compounds, types of radicals, and properties of various inorganic salts. This quiz covers essential concepts such as ionization, sublimation, and the appearance of different metal salts.
