Qualitative Analysis Quiz

When heated, zinc salts produce a yellow residue that turns white when cooled.

When heated in a dry test tube, copper sulfate forms a white residue and water condenses on the colder walls.

Carbonate radicals produce carbon dioxide (CO2) when heated.

Cadmium salts produce a brown residue that remains brown even when cool.

A white residue in a dry heating test indicates the absence of Cu2+, Fe2+, Ni2+, Mn2+, Co2+, Cr3+, Cd2+, Zn2+, and Pb2+.

A reducing flame is used for the Charcoal Cavity Test. It's produced by closing the air holes of a Bunsen burner.

Cobalt nitrate is a reagent used in the cobalt nitrate test. Excess cobalt nitrate can form black cobalt oxide, which masks the colors of other metals.

In the flame test, sodium emits a yellow color because its electrons get excited to a higher energy level and then release energy as they return to their ground state.

Glass contains sodium silicate, which gives a yellow color to the flame. This would interfere with the identification of other ions.

Platinum is chemically inert and does not react with acids or impart color to the flame, making it suitable for observing the color of the tested substance.

Barium salts are less volatile (easily vaporized) than other salts, and therefore take longer to show their characteristic color in the flame.

Lead can form an alloy with platinum, causing the wire to corrode and become unusable. This would interfere with subsequent tests.

Excess salt would result in an opaque bead, obscuring the color of the flame and hindering the identification of the metal.

White salts do not contain elements that produce colored meta-borates, making the test ineffective for identifying them.

Dilute sulfuric acid releases the gas characteristics of the salt and does not interfere with the identification of the gas, unlike dilute hydrochloric acid.

The water extract contains soluble ions, allowing for accurate identification of the presence of specific radicals, like nitrate, nitrite, and acetate ions.

KMnO4 acts as a self-indicator in titrations because its excess creates a distinct pink color when the reaction is complete.

The end point in KMnO4 titrations is when the solution transitions from colorless to a permanent light pink color, signifying the completion of the reaction.

Mohr's salt is preferred over ferrous sulphate in volumetric analysis because it's more stable and resists oxidation by air, ensuring accuracy in the results.

A few drops of conc. sulphuric acid are added when preparing a standard solution of Mohr's salt to prevent the hydrolysis of ferrous sulphate, which could affect its accurate concentration.

A burette with a rubber pinch cock should not be used in KMnO4 titrations because KMnO4 attacks rubber, potentially causing leaks and inaccurate results.

Gas that turns limewater milky. It's produced when carbonates react with acids.

A solution of calcium hydroxide (Ca(OH)2) in water. It's used to test for the presence of carbon dioxide.

A chemical test to identify nitrates. A brown ring forms at the junction of concentrated sulfuric acid and a solution containing nitrates and ferrous sulfate.

A reagent used to detect the presence of aldehydes. It's a solution of silver ions in ammonia.

Ammonical silver nitrate solution. It's used to detect aldehydes, which reduce the silver ions to metallic silver, forming a silver mirror on the inside of the test tube.

A reagent used to detect the presence of nitrates. It reacts with nitrates in the presence of concentrated sulfuric acid to form a blue-colored solution.

A colorless gas with a pungent odor. It turns lead acetate paper black. This can be used to test for the presence of sulfides.

A white precipitate that forms when carbon dioxide is bubbled through limewater. It's insoluble in water, but dissolves in excess carbon dioxide.

A solution whose concentration is precisely known.

One gram-equivalent mass of solute dissolved in one liter of solution.

The mass of a substance that reacts with or provides one mole of electrons.

The process of adding a solution of known concentration (titrant) from a burette to a solution of unknown concentration (analyte) until the reaction is complete.

A substance that changes color at the endpoint of a titration, indicating the reaction is complete.

The concentration of a solution expressed as moles of solute per liter of solution.

The concentration of a solution expressed as moles of solute per kilogram of solvent.

A substance that reacts with or provides one mole of hydrogen ions (H+).

Sodium nitroprusside is a chemical compound with the formula Na2[Fe(CN)5NO]. It is used in various applications, including as a reagent in analytical chemistry and as a vasodilator drug.

The chromyl chloride test is a chemical test used to detect the presence of chloride ions (Cl-) in a sample. It involves reacting the sample with potassium dichromate (K2Cr2O7) and concentrated sulfuric acid (H2SO4) to form chromyl chloride (CrO2Cl2), a red-brown gas. The gas is then dissolved in water to form a yellow solution of chromic acid (H2CrO4), which can be further tested to confirm the presence of chloride.

The carbon disulfide test is a chemical test used to detect the presence of bromide (Br-) or iodide (I-) ions in a sample. It involves reacting the sample with chlorine water (Cl2) in the presence of carbon disulfide (CS2). The chlorine displaces the bromide or iodide ions, which then dissolve in carbon disulfide to produce a characteristic color. Bromine gives an orange color, while iodine gives a violet color.

Bromides and iodides do not respond to the chromyl chloride test because they do not form stable chromyl compounds like chromyl chloride (CrO2Cl2). Instead, they release bromine (Br2) and iodine (I2) gas when reacted with concentrated sulfuric acid and potassium dichromate.

The matchstick test is a chemical test used to detect the presence of sulfate ions (SO4^2-) in a sample. It involves heating the sample with a matchstick, which causes a reduction of the sulfate to sulfide (S^2-). The sulfide then reacts with sodium nitroprusside to form a violet colored complex, indicating the presence of sulfate.

The blue color produced when iodine reacts with starch solution is due to the physical adsorption of iodine molecules onto the starch molecules. The iodine molecules get trapped within the helical structure of the starch molecules, resulting in the characteristic blue color.

Concentrated nitric acid (HNO3) is not used to prepare hydrogen sulfide (H2S) because it is a strong oxidizing agent that would oxidize H2S to elemental sulfur (S) and other products. This would result in a yellow precipitate of sulfur.

It's essential to add dilute hydrochloric acid (HCl) before proceeding to the test for basic radicals in group II because this creates an environment where only group II cations will precipitate out as sulfides. The HCl helps to reduce the concentration of sulfide ions, preventing the precipitation of the group III and IV cations which have higher solubility products.