Chemical analysis questions

By Interwoven Maths

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 does a melting range usually suggest about a sample?
  1. It contains more than one substance
  2. It is a pure compound
  3. It is a pure element
  4. It has a low boiling point

Question 2

Why do impurities often lower a substance's melting point?
  1. Different particles disrupt its regular structure
  2. Different particles strengthen its regular structure
  3. Extra particles make the structure more regular
  4. Impurities act as a catalyst for melting

Question 3

What is a formulation?
  1. A measured mixture designed for a purpose
  2. A mixture with uncontrolled proportions
  3. A pure compound with a fixed formula
  4. A product formed accidentally in a reaction

Question 4

Which ratio gives the chromatography Rf value?
  1. Substance distance ÷ solvent-front distance
  2. Solvent-front distance ÷ substance distance
  3. Baseline distance ÷ paper length
  4. Substance distance × solvent-front distance

Question 5

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 6

Why is a chromatography baseline drawn in pencil?
  1. Graphite does not dissolve in the solvent
  2. Graphite travels with the solvent front
  3. Graphite reacts with the dye spots
  4. Graphite raises the solvent's boiling point

Question 7

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
  4. A formulation containing surfactants

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. Damp blue litmus turns red then bleaches

Question 9

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 decolourises

Question 10

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 11

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

Question 12

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

Question 13

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

Question 14

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 15

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

Question 16

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 colourless solution

Question 17

Which test identifies carbonate ions?
  1. Add dilute acid; test the gas with limewater
  2. Add acidified barium chloride; look for a white precipitate
  3. Add acidified silver nitrate; look for a white precipitate
  4. Add sodium hydroxide; look for a blue precipitate

Question 18

Compared with simple chemical tests, instrumental methods are often:
  1. More sensitive and faster
  2. Less sensitive but faster
  3. More sensitive but slower
  4. Limited to pure substances

Question 19

Which white hydroxide precipitate dissolves in excess sodium hydroxide?
  1. Aluminium hydroxide
  2. Calcium hydroxide
  3. Magnesium hydroxide
  4. Copper(II) hydroxide

Question 20

Why is calibration needed in instrumental analysis?
  1. To match instrument response with known standards
  2. To make unknown samples produce matching peaks
  3. To remove impurities before measurement
  4. To choose units after collecting results

Question 21

When can an unknown spot be identified by matching its Rf value?
  1. When both chromatograms use the same conditions
  2. When different solvents give the same colour
  3. When the unknown travels beyond the solvent front
  4. When both samples begin at different baselines

Question 22

Why must chromatography samples start above the solvent level?
  1. To stop them dissolving into the reservoir
  2. To stop the solvent rising through the paper
  3. To make every substance move at the same rate
  4. To keep the solvent front at the baseline

Question 23

What flame colour indicates lithium ions?
  1. Crimson
  2. Yellow
  3. Lilac
  4. Green

Question 24

What flame colour indicates calcium ions?
  1. Orange-red
  2. Crimson
  3. Yellow
  4. Lilac

Question 25

Which test identifies sulfate ions?
  1. Acidified barium chloride gives a white precipitate
  2. Acidified silver nitrate gives a white precipitate
  3. Dilute acid releases gas that clouds limewater
  4. Sodium hydroxide gives a blue precipitate

Question 26

Which test identifies chloride ions?
  1. Acidified silver nitrate gives a white precipitate
  2. Acidified barium chloride gives a white precipitate
  3. Dilute acid releases gas that clouds limewater
  4. Sodium hydroxide gives a green precipitate

Question 27

Which method can identify metal ions at very low concentrations?
  1. Flame emission spectroscopy
  2. Paper chromatography
  3. Acid-base titration
  4. Simple distillation

Question 28

What does flame emission spectroscopy produce for a metal ion?
  1. A characteristic line spectrum
  2. A universal continuous spectrum
  3. A mass spectrum of molecular fragments
  4. An infrared absorption spectrum

Question 29

What is a precipitate?
  1. An insoluble solid formed in a reaction
  2. A gas released during a reaction
  3. A soluble product remaining in solution
  4. A substance that speeds up a reaction

Question 30

What can a calibration curve determine?
  1. An unknown concentration from instrument response
  2. A sample's purity by filtration
  3. A gas identity from its smell
  4. A chromatography solvent from colour

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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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