Experimental Chemistry Notes PDF

**1.1 Physical Quantities** **Physical Quantity** **Apparatus used** **Diagram** **SI Unit** **Degree of accuracy** ----------------------- ------------------------ ----------------------- ------------- ------------------------------------------- **Mass**...

**1.1 Physical Quantities** **Physical Quantity** **Apparatus used** **Diagram** **SI Unit** **Degree of accuracy** ----------------------- ------------------------ ----------------------- ------------- ------------------------------------------- **Mass** **electronic balance** **kg** **Nearest 0.01 g** **Temperature** **thermometer** **K** **Nearest 0.5 ^o^C** **Time** **stopwatch** **s** **Nearest 0.01 s** **Volume of gas** **gas syringe**  **m^3^** **Measures up to 100 cm^3^** **Volume of liquid** **measuring cylinder** **m^3^** **Nearest 0.5 cm^3^** **pipette**  **m^3^** **Measures fixed volumes e.g 25.0 cm^3^** **burette** **m^3^** **Nearest 0.05 cm^3^** **Collecting Gases** +-------------+-------------+-------------+-------------+-------------+ | Method | **water | **upward | **downward | **gas | | ------ | displacemen | delivery** | delivery** | syringe** | | | t** | | | | +=============+=============+=============+=============+=============+ | |  | | mage9.png) | | +-------------+-------------+-------------+-------------+-------------+ | **To | Insoluble | Soluble in | Soluble in | Any gas, | | collect | in water | water, | water, | | | gases that | | | | Measure | | are** | | Less dense | More dense | volume of | | | | than air | than air | gas in | | | | | | **cm^3^** | +-------------+-------------+-------------+-------------+-------------+ | **Examples | **carbon | **ammonia** | **chlorine, | | | of gases** | dioxide, | | \ | | | | hydrogen, | | hydrogen | | | | oxygen** | | chloride** | | +-------------+-------------+-------------+-------------+-------------+ **1.2 Separation Techniques and Methods of Purification** +-----------------------------------------------------------------------+ | **Filtration** | +=======================================================================+ | - | | | | | | | | - Eg. Separating [sand and water], [chalk and | | water] | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ | **Using suitable solvents (dissolution)** | +-----------------------------------------------------------------------+ | - **To separate a soluble solid -- insoluble solid mixture** | | | | - Used when **only one solid is soluble** in a particular solvent | | (eg. water, ethanol) | | | | - Eg. Separating a mixture of [salt and sand] | | | | +---------------------+---------------------+---------------------+ | | | **Mixture** | **Solvent Used** | **Steps** | | | +---------------------+---------------------+---------------------+ | | | Salt (soluble) and | Water | 1\. Add | | | | Sand (insoluble) | | **distilled | | | | | | water** to the | | | | | | mixture of salt | | | | | | and sand **to | | | | | | dissolve** **the | | | | | | salt**. | | | | | | | | | | | | 2\. **Filter** | | | | | | mixture using a | | | | | | filter funnel and | | | | | | filter paper. | | | | | | | | | | | | 3\. **Wash | | | | | | residue** with | | | | | | distilled water. | | | | | | | | | | | | 4\. **Sand** is | | | | | | collected as | | | | | | **residue** and | | | | | | **salt solution** | | | | | | collected as | | | | | | **filtrate**. | | | +---------------------+---------------------+---------------------+ | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ | A solid dissolves in a liquid to produce a **solution.** | | | | The solid that dissolves is called a **solute** and the liquid is | | called a **solvent.** | | | | **solute + solvent solution**[\ | | ] | | | | **Evaporation** and **Crystallisation** can be used to obtain a | | **soluble** solid from its solution. | +-----------------------------------------------------------------------+ +-----------------------------------------------------------------------+ | **Evaporation to Dryness** | +=======================================================================+ | - **To separate a solute -- solvent mixture (Soluble Solid -- | | Liquid mixture)** | | | | **Steps:\ | | (a)** Place the solution in an evaporating dish.\ | | (b) Evaporate the solvent until **all** the solvent is removed. | | | | - Eg. **obtain salt from seawater** | | | | **Can all substances undergo evaporation to dryness?** | | | | - When a substance **decomposes** on heating, we **do not | | evaporate** it to dryness\ | | (eg. sugar decomposes to form water and carbon on strong | | heating). | | | | - **Crystallisation** is used instead. | +-----------------------------------------------------------------------+ | **Crystallisation** | +-----------------------------------------------------------------------+ | - **To separate a solute -- solvent mixture (Soluble Solid -- | | Liquid mixture)** | | | | 1. Heat the solution until it becomes **saturated**. | | | | 2. Leave the saturated solution **to cool and crystallise**. | | | | 3. **Filter** to obtain crystals. | | | | 4. **Wash** crystals with **small amount** of cold distilled water | | to remove impurities. | | | | 5. **Dry** the crystals between sheets of **filter paper**. | | | |  | | | | **Step 1 Step 2 Step 3 Step 4** | | | | - E.g: obtain [copper(II) sulfate crystals], [sugar | | crystals] | +-----------------------------------------------------------------------+ +-----------------------------------------------------------------------+ | **Simple Distillation** | +=======================================================================+ | - **To separate a solute -- solvent mixture (Soluble solid -- | | Liquid mixture)** | | | | - Simple distillation is the process of **boiling** a solution and | | then **condensing** the vapour to obtain the pure liquid. | | | | - Used to separate a pure solvent from a solution | | | | - E.g. obtaining [pure water from sea water] | | | | **[General Parts of a distillation set-up]** | | | | **Part** **Purpose** | | --------------- --------------------------------------------------- | | --------------------------------------------------------------------- | | --------------------------------------------------------------------- | | --- | | Thermometer To **measure temperature of pure vapour (boiling po | | int)** just before it enters the condenser. | | **[Precaution]**: Bulb of thermometer s | | hould be placed beside the side-arm of the flask for accurate measure | | ment. | | Boiling chips To **ensure smooth boiling** | | Condenser To **cool and condense** hot **vapour into a liquid | | **. | | **[Precaution]**: Cold water should pas | | s over the condenser by entering the bottom and leaving from the top | | Beaker To collect the pure distillate. | | **[Precaution]**: If distillate is **vo | | latile**, the beaker should be surrounded with ice (or kept in an ice | | bath) to keep the temperature low so that it remains in liquid state | |. | +-----------------------------------------------------------------------+ | **Fractional Distillation** | +-----------------------------------------------------------------------+ | - **To separate a Liquid -- Liquid mixture (Miscible Liquids)** | | | | - **Miscible liquids** are **[liquids that can be mixed completely | | to form a single layer]** | | | | - Eg. Used to separate a mixture of liquid and liquid that have | | **different boiling points**. Ethanol (b.p. = 78 °C) and water | | (b.p. = 100 °C). | | | | - The liquid with the **lower boiling point** (ethanol) distils | | over first. | | | | - The **fractionating column** provides the surface area for | | repeated | | | | | | | | - As the vapours rise up the column, the **less volatile (higher | | boiling point)** substance condenses and drops back into the | | flask while the **more volatile (lower boiling point)** substance | | rises up the fractionating column. | | | |  | | | | **Graph of Temperature against Time for fractional distillation of | | ethanol -- water mixture** | | | | **\ | | Industrial application of fractional distillation:** | | | | **(a)** Fractional distillation of **[liquid air]** to | | obtain nitrogen, argon and oxygen. | | | | **(b)** Fractional distillation of **[petroleum / crude | | oil]** to obtain petrol, diesel, kerosene, etc | | | | **(c)** Fractional distillation of **[fermented liquor]** | | to obtain ethanol. | | | | **Differences between Simple and Fractional Distillation** | | | | **Simple Distillation** | | **Fractional Distillation** | | ------------------------------------------------------------------- | | ------------------------- ------------------------------------------- | | ----------------------------------------------------------------- | | No fractionating column | | Fractionating column present | | To obtain **[a liquid]** from a **[soluble solid-liquid | | ]** mixture To obtain one or more **[liquids]{.underlin | | e}** from a **[liquid-liquid]** mixture | | Substances must have **different boiling points** | | Liquids in mixture must be **[miscible]{.un | | derline}** and have **[different boiling points]**. | +-----------------------------------------------------------------------+ | **\ | | Using a magnet** | +-----------------------------------------------------------------------+ | | +-----------------------------------------------------------------------+ **\ ** +-----------------------------------------------------------------------+ | **\ | | Chromatography** | +=======================================================================+ | - **To separate a Liquid -- Liquid mixture (Miscible Liquids) or | | dissolved solids** | | | | - Used to separate a mixture of substances that have **different | | solubilities in a given solvent**. Eg food colourings, dyes, | | blood sample etc | | | | - The substance which is **more soluble in the solvent** move more | | quickly and further up. | | | | - The **start line** is always marked with a substance that is | | **insoluble in the solvent** eg graphite pencil | | | | +--------------------------------+--------------------------------+ | | | **Chromatography set-up** | **Chromatogram (result of | | | | | chromatography experiment)** | | | +================================+================================+ | | |  | | | | +--------------------------------+--------------------------------+ | | | | [Circular | | | | | chromatogram] | | | | | [Linear | | | | | chromatogram] | | | | | | | | | |  | | | +--------------------------------+--------------------------------+ | | | | +---------------------+---------------------+---------------------+ | | | **Type** | **Description** | **Diagram** | | | +=====================+=====================+=====================+ | | | Pure dye | Only one spot | | | | +---------------------+---------------------+---------------------+ | | | Insoluble dyes | Remains at the | | | | | | start line | | | | +---------------------+---------------------+---------------------+ | | | Same dyes | Move equal distance | | | | | | from start line | | | | +---------------------+---------------------+---------------------+ | | | | - Dye G pure dye | | | | | | | | | | | | - Dye F insoluble | | | | | | dye | | | | | | | | | | | | - Dye E and H are | | | | | | mixtures and | | | | | | contain one dye | | | | | | that is the | | | | | | same | | | | +---------------------+---------------------+---------------------+ | +-----------------------------------------------------------------------+ **1.3 Methods to Test for the Purity of a Substance** The purity of a substance can be tested by: **i) Melting Point and Boiling Point Determination\ ** a. b. c. **ii) Chromatography** a.