Chemical analysis questions

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Chemical analysis question collection

Review Chemical analysis questions for Chemistry, with correct answers shown and coverage across pure substances and formulations; chromatography; gas tests.

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Question 1

What is chromatography used for?
  1. Separating mixtures of dissolved substances
  2. Measuring pH only
  3. Balancing symbol equations
  4. Counting protons in atoms

Question 2

In paper chromatography, the solvent is called the?
  1. Mobile phase
  2. Stationary phase
  3. Catalyst phase
  4. Indicator phase

Question 3

In paper chromatography, the paper is the?
  1. Stationary phase
  2. Mobile phase
  3. Reactant phase
  4. Gas phase

Question 4

Why must the baseline be drawn in pencil for chromatography?
  1. Pencil graphite does not dissolve in the solvent
  2. Pencil lines are brighter than ink
  3. Ink stops substances moving
  4. Pencil adds a useful indicator color

Question 5

If a sample gives one spot on a chromatogram (in one solvent), it is likely to be?
  1. A pure substance
  2. A mixture of at least three substances
  3. Definitely an element only
  4. Always a gas

Question 6

If a sample gives several spots on a chromatogram, it is likely to be?
  1. A mixture
  2. A pure compound
  3. A catalyst
  4. A neutral solution only

Question 7

What is the test for oxygen gas?
  1. A glowing splint relights
  2. A lit splint gives a squeaky pop
  3. Limewater turns milky
  4. Damp red litmus turns blue

Question 8

What is the test for hydrogen gas?
  1. A lit splint gives a squeaky pop
  2. A glowing splint relights
  3. Limewater turns milky
  4. Orange bromine water decolorizes

Question 9

What is the test for carbon dioxide gas?
  1. Limewater turns milky
  2. A glowing splint relights
  3. A lit splint gives a pop
  4. Damp blue litmus turns red

Question 10

Which gas bleaches damp litmus paper?
  1. Chlorine
  2. Hydrogen
  3. Oxygen
  4. Nitrogen

Question 11

What color is universal indicator in a strong acid?
  1. Red
  2. Green
  3. Blue
  4. Purple

Question 12

What color is universal indicator in a neutral solution?
  1. Green
  2. Red
  3. Blue
  4. Orange

Question 13

How would you classify a solution with pH 2?
  1. Strongly acidic
  2. Neutral
  3. Weakly alkaline
  4. Strongly alkaline

Question 14

How would you classify a solution with pH 11?
  1. Alkaline
  2. Acidic
  3. Neutral
  4. Always pure water

Question 15

What does the symbol equation \(\mathrm{HCl} + \mathrm{NaOH} \to \mathrm{NaCl} + \mathrm{H}_2\mathrm{O}\) represent?
  1. Neutralisation
  2. Combustion
  3. Thermal decomposition
  4. Displacement

Question 16

Why do chemists often compare an unknown chromatogram with known standards?
  1. To help identify substances by matching spot positions
  2. To change the pH of the unknown
  3. To increase reaction rate only
  4. To add more solute to the unknown

Question 17

If two spots travel the same distance in the same solvent, this suggests the substances?
  1. May be the same substance
  2. Must be different elements
  3. Are definitely both acids
  4. Are always pure metals

Question 18

In a gas test, why should the test gas be fresh and the splint damp/dry as required?
  1. To make the test result reliable
  2. To make the reaction exothermic
  3. To prevent ions from forming
  4. To increase atom mass number

Question 19

A student records pH as 7 for a solution. Which statement is best?
  1. The solution is neutral
  2. The solution is strongly acidic
  3. The solution is strongly alkaline
  4. pH 7 means there is no water present

Question 20

Which test would confirm that an unknown gas is carbon dioxide?
  1. Bubble it through limewater and observe it turning milky
  2. Use a lit splint and listen for a squeaky pop
  3. Use a glowing splint and observe relighting
  4. Add bromine water and look for decolorization

Question 21

A pure substance has a sharp melting point. What does a melting range usually suggest?
  1. The sample is impure
  2. The sample is definitely an element
  3. The sample must be a gas
  4. The sample has no particles

Question 22

Why do impure substances often have a lower melting point than pure substances?
  1. Different particles disrupt the regular structure
  2. Impurities always increase bond strength
  3. Impure samples contain no intermolecular forces
  4. Impurities remove all atoms of the main substance

Question 23

What is a formulation?
  1. A mixture designed for a useful purpose with carefully measured components
  2. A pure element in solid form
  3. A compound with one type of atom only
  4. A reaction that always reaches equilibrium

Question 24

In paper chromatography, the Rf value is calculated as?
  1. Distance moved by substance / distance moved by solvent front
  2. Distance moved by solvent front / distance moved by substance
  3. Distance moved by baseline / distance moved by solvent
  4. Distance moved by substance x solvent front distance

Question 25

If a dye spot moves \(3.0\,\mathrm{cm}\) and the solvent front moves \(6.0\,\mathrm{cm}\), what is Rf?
  1. \(0.50\)
  2. \(2.0\)
  3. \(3.0\)
  4. \(0.20\)

Question 26

Why is the baseline drawn in pencil in chromatography?
  1. Pencil graphite does not dissolve in the solvent
  2. Pencil ink moves faster than solvent
  3. Pencil increases Rf values
  4. Pencil reacts with all dyes

Question 27

What does one spot on a chromatogram (in a given solvent) usually indicate?
  1. A pure substance
  2. A mixture of at least two substances
  3. A metal ion solution only
  4. A formulation containing surfactants

Question 28

What is the test for hydrogen gas?
  1. A lit splint gives a squeaky pop
  2. A glowing splint relights
  3. Limewater turns milky
  4. Damp blue litmus turns red then bleaches

Question 29

What is the test for oxygen gas?
  1. A glowing splint relights
  2. A lit splint gives a squeaky pop
  3. Limewater turns cloudy
  4. Bromine water decolorizes

Question 30

What is the test for carbon dioxide gas?
  1. Limewater turns milky
  2. A glowing splint relights
  3. A lit splint gives a squeaky pop
  4. Damp red litmus turns blue

Question 31

Chlorine gas bleaches damp litmus paper. What color change is first seen on blue litmus?
  1. Blue to red, then bleached white
  2. Blue to green only
  3. Blue to purple only
  4. No change on damp litmus

Question 32

Which flame test color indicates sodium ions, \(\mathrm{Na^+}\)?
  1. Yellow
  2. Lilac
  3. Green
  4. Brick red

Question 33

Which flame color is characteristic of potassium ions, \(\mathrm{K^+}\)?
  1. Lilac
  2. Yellow
  3. Blue-green
  4. Orange-red

Question 34

Adding sodium hydroxide to Cu2+ solution produces what observation?
  1. A blue precipitate
  2. A green precipitate
  3. A white precipitate
  4. No precipitate

Question 35

What observation is seen when sodium hydroxide is added to Fe2+ solution?
  1. A green precipitate
  2. A blue precipitate
  3. A white precipitate
  4. A yellow solution only

Question 36

What observation is seen when sodium hydroxide is added to Fe3+ solution?
  1. A brown precipitate
  2. A green precipitate
  3. A blue precipitate
  4. A colorless solution

Question 37

How can carbonate ions (CO32-) be identified?
  1. Add dilute acid and test the gas with limewater
  2. Add sodium hydroxide and look for lilac flame
  3. Add bromine water and look for decolorization
  4. Heat strongly and test for hydrogen pop

Question 38

What is the main advantage of instrumental methods compared with simple chemical tests?
  1. They are often more sensitive and can analyse mixtures quickly
  2. They never require calibration
  3. They cannot detect small amounts
  4. They replace all practical chemistry entirely

Question 39

What can be identified using a unique set of absorption peaks in an infrared spectrum?
  1. A molecule
  2. Only the color of a solution
  3. Only atomic number
  4. Only concentration in mol/dm3 without standards

Question 40

Why is calibration needed in instrumental analysis?
  1. To compare measurements with known standards and improve accuracy
  2. To make all unknowns show identical peaks
  3. To remove impurities from the sample chemically
  4. To avoid using any units in results

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Review Chemical analysis questions for Chemistry, with correct answers shown and coverage across pure substances and formulations; chromatography; gas tests.

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