🔬 • Lesson 2.9 : Experiments and Chemical Analysis (Chem)

Question 1

What apparatus is used to measure time?

Answer 1

Stop-watch.

Question 2

What apparatus is used to measure temperature?

Answer 2

Thermometer.

Question 3

What apparatus is used to measure mass?

Answer 3

Balance.

Question 4

What apparatus is used to measure volume in titration?

Answer 4

Burette.

Question 5

What apparatus is used to measure a specific volume of liquid accurately?

Answer 5

Volumetric pipette.

Question 6

What apparatus is used to measure approximate volumes of liquids?

Answer 6

Measuring cylinder.

Question 7

What apparatus is used to measure the volume of gas?

Answer 7

Gas syringe.

Question 8

What is a solvent?

Answer 8

A substance that dissolves a solute.

Question 9

What is a solute?

Answer 9

A substance that is dissolved in a solvent.

Question 10

What is a solution?

Answer 10

A mixture of one or more solutes dissolved in a solvent.

Question 11

What is a saturated solution?

Answer 11

A solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature.

Question 12

What is a residue?

Answer 12

A solid substance that remains after evaporation, distillation, filtration, or similar processes.

Question 13

What is a filtrate?

Answer 13

A liquid or solution that has passed through a filter.

Question 14

Name 3 of the apparatus used to perform an acid-base titration?

Answer 14

Burette, volumetric pipette, indicator

Question 15

How is a burette used in an acid-base titration?

Answer 15

The volumetric pipette is used to measure an accurate volume of the solution to be titrated.

Question 16

How is a volumetric pipette used in titration?

Answer 16

The volumetric pipette is used to measure an accurate volume of the solution to be titrated.

Question 17

What is the role of an indicator in titration?

Answer 17

The indicator changes color at the end-point, showing when the reaction is complete.

Question 18

What is paper chromatography used for?

Answer 18

Paper chromatography separates mixtures of soluble colored substances to identify their components.

Question 19

How does paper chromatography separate substances?

Answer 19

Substances move at different speeds through a solvent based on their solubility and affinity for the paper.

Question 20

How do you identify unknown substances in chromatography?

Answer 20

Compare the Rf values of the unknown substance with known substances to identify it.

Question 21

How do you identify pure and impure substances in chromatography?

Answer 21

Pure substances have one spot on the chromatogram,
Impure substances show multiple spots.

Question 22

What is the Rf equation in chromatography?

Answer 22

Rf = (distance traveled by substance) / (distance traveled by solvent).

The Rf value helps to identify substances.

Question 23

How is separation and purification done using a suitable solvent?

Answer 23

A solvent dissolves the solute, separating it from the residue. After, the solution can be filtered or evaporated to purify.

Question 24

How does filtration work for separation and purification?

Answer 24

Filtration separates solids from liquids using filter paper.
The liquid that passes through is called the filtrate.

Question 25

How does crystallisation work for separation and purification?

Answer 25

Crystallisation separates a dissolved solid by cooling the solution, allowing crystals to form and be collected by filtration.

Question 26

How does simple distillation work for separation and purification?

Answer 26

Simple distillation separates liquids based on boiling points. The substance with a lower boiling point evaporates, condenses, and is collected.

Question 27

How does fractional distillation work for separation and purification?

Answer 27

Fractional distillation separates mixtures of liquids with different boiling points by using a fractionating column to allow multiple distillations.

Question 28

What *separation technique* would you use for a mixture of two liquids with different boiling points?

Answer 28

**Fractional distillation** is best for separating liquids with different boiling points.

Question 29

How can purity be assessed from melting point and boiling point?

Answer 29

A pure substance has a *sharp, specific melting and boiling point.* Impurities lower the melting point and widen the boiling point range.

Question 30

How do you test for **carbonate ions** (CO₃²⁻)?

Answer 30

Add dilute acid. If carbon dioxide (CO₂) is produced, bubble it through limewater, which will turn cloudy.

Question 31

How do you test for chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻) ions?

Answer 31

*Acidify with dilute nitric acid, then add aqueous silver nitrate.* • Chloride: White precipitate (AgCl). • Bromide: Cream precipitate (AgBr). • Iodide: Yellow precipitate (AgI).

Question 32

How do you test for **nitrate ions** (NO₃⁻)?

Answer 32

Add aluminum foil and aqueous sodium hydroxide, then warm. If ammonia gas (NH₃) is produced, nitrate ions are present.

Question 33

How do you test for **sulfate ions** (SO₄²⁻)?

Answer 33

Acidify with dilute nitric acid, then add aqueous barium nitrate. A **white** precipitate (BaSO₄) indicates sulfate ions.

Question 34

How do you test for **ammonium ions** (NH₄⁺)?

Answer 34

Add aqueous sodium hydroxide and warm. If ammonia gas (NH₃) is released, ammonium ions are present.

Question 35

How do you test for **calcium ions** (Ca²⁺)?

Answer 35

Add aqueous sodium hydroxide. A **white** precipitate (Ca(OH)₂) indicates calcium ions.

Question 36

How do you test for **copper(II) ions** (Cu²⁺)?

Answer 36

Add aqueous sodium hydroxide. A **blue** precipitate (Cu(OH)₂) forms.

Question 37

How do you test for **iron(II) ions** (Fe²⁺)?

Answer 37

Add aqueous sodium hydroxide. A **green** precipitate (Fe(OH)₂) forms.

Question 38

How do you test for **iron(III) ions** (Fe³⁺)?

Answer 38

Add aqueous sodium hydroxide. A **brown** precipitate (Fe(OH)₃) forms.

Question 39

How do you test for **zinc ions** (Zn²⁺)?

Answer 39

Add aqueous sodium hydroxide. A **white** precipitate (Zn(OH)₂) forms, which dissolves in excess sodium hydroxide to form a **colorless** solution.

Question 40

How do you test for **ammonia gas** (NH₃)?

Answer 40

Damp red litmus paper turns **blue** when exposed to ammonia gas.

Question 41

How do you test for **carbon dioxide** (CO₂)?

Answer 41

Bubble CO₂ through **limewater**. It turns cloudy if CO₂ is present.

Question 42

How do you test for **chlorine gas** (Cl₂)?

Answer 42

Damp litmus paper turns **white** when exposed to chlorine gas.

Question 43

How do you test for **hydrogen gas** (H₂)?

Answer 43

Hold a lighted splint near hydrogen gas. It will produce a **pop sound.**

Question 44

How do you test for **oxygen gas** (O₂)?

Answer 44

Insert a glowing splint into the gas. If oxygen is present, the splint will **reignite.**

Question 45

How do you use a flame test to identify **lithium ions** (Li⁺)?

Answer 45

Lithium gives a **crimson red flame.**

Question 46

How do you use a flame test to identify **sodium ions** (Na⁺)?

Answer 46

Sodium gives a **yellow flame.**

Question 47

How do you use a flame test to identify **potassium ions** (K⁺)?

Answer 47

Potassium gives a **lilac flame.**

Question 48

How do you use a flame test to identify **copper(II) ions** (Cu²⁺)?

Answer 48

Copper gives a green flame.

Question 49

How do you test for carbon dioxide gas (CO₂) using a splint?

Answer 49

Light a splint and place it into a container of the gas. The splint **goes out.** (This happens because CO₂ is not flammable and does not support combustion.)

Question 50

How do you use a flame test to identify **calcium ions** (Ca²⁺)?

Answer 50

Calcium gives a **orange-red flame.**