SITEMAP *  HOME PAGE * SEARCH * UK KS3 level Science Quizzes for students aged ~13-14

UK GCSE level BiologyChemistryPhysics ~14-16 * Advanced pre-university Chemistry ~16-18

GCSE level Chemistry: Revision notes on how to prepare and collect common gases

Doc Brown's Chemistry Revision Notes (re-edit)

Gas preparation and collection methods revision notes

This page describes a variety of methods and techniques for preparing and collecting gases - summarised details including diagrams of the apparatus, the chemicals-reagents needed, and the gas preparation reaction equations


email doc brown - comments - query?

Detailed notes on chemical identification tests

Shortened version of chemical tests for GCSE level students

methods of gas preparation - apparatus, chemicals and equation (c) doc bNotes on gas collection method

The method of collecting the gas depends on its density relative to air, unless you collect the gas over water in an inverted test tube - then it doesn't matter.

If the gas is less dense than air e.g. hydrogen or ammonia, the test tube must be inverted and the gas will rise into it to displace the more dense air.

If the gas is heavier than air e.g. carbon dioxide or chlorine (in fume cupboard), the test tube is in its normal upright position and the gas will sink in displacing the less dense air.

methods of gas preparation - apparatus, chemicals and equation (c) doc bAlphabetical index of gas preparations

ammonia NH3

carbon dioxide CO2

cracking hydrocarbons to make alkenes CH2=CH2

chlorine Cl2

drying gases dehydrating agents

hydrogen H2

hydrogen chloride HCl

nitrogen dioxide NO2

oxygen O2

sulfur dioxide SO2

HAZARD WARNING SYMBOLS

TOP OF PAGE - INDEX

methods of gas preparation - apparatus, chemicals and equation (c) doc b

Ex 1. How can you prepare ammonia gas?

Apparatus and method for preparing a sample of ammonia gas

Procedure for preparing and collecting a gas less dense (lighter) than air by heating solid reactants. The less dense gas rises into, and displaces, the more dense air downwards. This method of gas preparation is called upward delivery.

e.g. methods of gas preparation - apparatus, chemicals and equation (c) doc bHeating a mixture of ammonium chloride and calcium hydroxide solids gives ammonia which has a very pungent odour! and turns red litmus blue. See also method Ex 7. method as an alternative.

2NH4Cl(s) + Ca(OH)2(s) ==> CaCl2(s) + 2H2O(l) + 2NH3(g) 

To make dry ammonia you need a U tube packed with granules of calcium oxide between the horizontal pyrex tube and the vertical inverted collection test tube.

methods of gas preparation - apparatus, chemicals and equation (c) doc b

Ex 2. How can you prepare hydrogen gas?

Apparatus and method for preparing a sample of hydrogen gas

Procedure for preparing and collecting a gas less dense (lighter) than air by reacting a liquid and a solid. The less dense gas rises into, and displaces, the more dense air downwards. This method of gas preparation is called upward delivery.

methods of gas preparation - apparatus, chemicals and equation (c) doc bmethods of gas preparation - apparatus, chemicals and equation (c) doc be.g. A mixture of zinc and hydrochloric acid makes hydrogen. Hydrogen gives a squeaky pop! with a lit splint. See also methods Ex 5., Ex 6. and Ex 7. which can be used.

Zn(s) + 2HCl(aq) ==> ZnCl2(aq) + H2(g) 

 methods of gas preparation - apparatus, chemicals and equation (c) doc b

Ex 3. How can you prepare nitrogen dioxide gas?

Apparatus and method for preparing a sample of nitrogen dioxide gas

Procedure for preparing and collecting a gas more dense (heavier) than air by heating the reactants. The more dense gas sinks down into, and displaces, the less dense air upwards. This method of gas preparation is called downward delivery.

eg methods of gas preparation - apparatus, chemicals and equation (c) doc bmethods of gas preparation - apparatus, chemicals and equation (c) doc bMaking nasty brown nitrogen dioxide (nitrogen(IV) oxide) by heating lead(II) nitrate crystals (thermal decomposition). The solid 'deflacrates', it crackles as the gas formed splits the crystals apart. See also method Ex 7. as an alternative.

2Pb(NO3)2(s) ==> 2PbO(s) + 4NO2(g) + O2(g) 

Ex 4. Method for preparing and collecting a gas more dense (heavier) than air by reacting a solid and a liquid. The more dense gas sinks down into, and displaces, the less dense air upwards.  This is called downward delivery. Examples:

methods of gas preparation - apparatus, chemicals and equation (c) doc b 

Procedure - how can you prepare carbon dioxide gas?

Apparatus and method for preparing a sample of carbon dioxide gas

This method of gas collection is called downward delivery.

(i) Calcium carbonate (limestone/marble chips) with hydrochloric acid makes carbon dioxide. Can also be done via Ex 6. but carbon dioxide is moderately soluble and does make 'carbonated water. See also Ex 8. for carbonate test.

CaCO3(s) + 2HCl(aq) ==> CaCl2(aq) + H2O(l) + CO2(g) 

 

Procedure - how can you prepare sulfur dioxide gas?

Apparatus and method for preparing a sample of sulfur dioxide gas

methods of gas preparation - apparatus, chemicals and equation (c) doc bmethods of gas preparation - apparatus, chemicals and equation (c) doc b(ii) Sulfur dioxide from solid sodium metabisulfite or sodium sulfite and excess dilute hydrochloric acid. The nasty choking gas turns potassium dichromate(VI) paper from orange to green. Should be done in fume cupboard.

Na2S2O5(s) + 2HCl(aq) ==> 2NaCl(aq) + H2O(l) + 2SO2(g) 

or Na2SO3(s) + 2HCl(aq) ==> 2NaCl(aq) + H2O(l) + SO2(g) 

 

Procedure - how can you prepare hydrogen chloride gas?

Apparatus and method for preparing a sample of hydrogen chloride gas

methods of gas preparation - apparatus, chemicals and equation (c) doc bmethods of gas preparation - apparatus, chemicals and equation (c) doc b(iii) Nasty acrid Hydrogen chloride is formed when conc. sulfuric acid is mixed with solid sodium chloride. Should be done in fume cupboard.

NaCl(s) + H2SO4(l) ==> NaHSO4(s) + HCl(g) 

 

Procedure - how can you prepare chlorine gas?

Apparatus and method for preparing a sample of chlorine gas

(iv) methods of gas preparation - apparatus, chemicals and equation (c) doc bmethods of gas preparation - apparatus, chemicals and equation (c) doc bChlorine from conc. sodium chlorate(I) and conc. hydrochloric acid.

Very dangerous and should be done in a fume cupboard.

NaClO(aq) + 2HCl(aq) ==> NaCl(aq) + H2O(l) + Cl2(g) 

or from the chemical reaction

conc. hydrochloric acid + damp potassium manganate(VII) crystals ==> chlorine gas + other products. The potassium manganate(VII), old name potassium permanganate, acts as an oxidising agent - it oxidises the chloride ion (Cl-) to chlorine molecules (Cl2).

All of these can be done via methods Ex. 5, Ex. 6 (its not too soluble and a way of making small amounts of 'chlorine water') or Ex 7.  described below.

methods of gas preparation - apparatus, chemicals and equation (c) doc b

Ex 5. Using a gas syringe collection system

Apparatus and method for preparing and collecting a gas of any density by reacting a solid and a liquid at room temperature. e.g. for making carbon dioxide Ex 4., chlorine Ex 4., hydrogen Ex 2., hydrogen chloride Ex 4., oxygen Ex 6., sulfur dioxide Ex 4.

 methods of gas preparation - apparatus, chemicals and equation (c) doc b

This is called collecting over water, or displacement of water or pneumatic trough collection.

Ex 6. How can you prepare oxygen gas?

Apparatus and method for preparing a sample of oxygen gas

This method of gas preparation is by water displacement

Method for preparing and collecting a gas of any density by reacting a solid-liquid, as long as the gas is not too soluble in water! (dissolving or reacting). All gases are less dense than liquid water and will displace the water downwards. No good for soluble gases like ammonia, hydrogen chloride, nitrogen dioxide or sulfur dioxide. You can collect in inverted gas jar if bigger sample required. You have to watch for 'sucking back' effects. Examples:

methods of gas preparation - apparatus, chemicals and equation (c) doc b(i) Making oxygen from hydrogen peroxide solution using manganese dioxide catalyst.

Oxygen has similar density to air so must be collected by method Ex 5 as the only alternative

2H2O2(aq) ==> 2H2O(l) + O2(g) 

(ii) Hydrogen, (iii) carbon dioxide and (iv) chlorine (moderately soluble, makes 'chlorine water')

methods of gas preparation - apparatus, chemicals and equation (c) doc bEx 7. Solid reactants - collecting gas in syringe

Apparatus and method for preparing and collecting a gas of any density by heating solids.

The angled boiling tube minimises the risk of contaminating the gas syringe with solids or liquids eg making ammonia or nitrogen dioxide. Its a smaller scale alternative to Ex 5. and using a Pyrex tube suitable for small scale heated experiments.

 methods of gas preparation - apparatus, chemicals and equation (c) doc b Ex 8. A simple way to test for a carbonate.

Add acid to the suspected carbonate. Collect a sample of the gas in a teat pipette from just above the reaction mixture. Bubble the gas sample into calcium hydroxide solution (limewater) and a milky white confirms the gas is carbon dioxide formed from the original carbonate.

See summary of tests needed by GCSE students

methods of gas preparation - apparatus, chemicals and equation (c) doc bU tube

methods of gas preparation - apparatus, chemicals and equation (c) doc bdreschel bottle

Ex 9. Use of a U tube. This is useful if the dry gas is needed. It is inserted in the apparatus set-up between the reaction container and the gas collection system. It is packed with a solid water absorbing drying agent e.g. anhydrous calcium chloride (not for ammonia), calcium oxide (not acidic gases like sulfur dioxide, carbon dioxide and chlorine), anhydrous sodium sulfate.

A dreschel bottle can also be used e.g. the gas is bubbled through concentrated sulfuric acid which will dry the gas. It cannot be used to dry alkaline gases like ammonia, with which it will react exothermically to form the solid salt ammonium sulfate.

methods of gas preparation - apparatus, chemicals and equation (c) doc b

How can you demonstrate the process of cracking hydrocarbons in the laboratory?

methods of gas preparation - apparatus, chemicals and equation (c) doc bEx 10. A cracking experiment.

This diagram outlines a way of demonstrating high temperature thermal cracking of larger hydrocarbon alkanes like paraffin oil/wax into smaller molecules i.e. smaller/lower alkanes and alkenes.

 

This is a thermal decomposition reaction catalysed by aluminium oxide (or broken porous pot).

The gases produced can be tested with (i) a match! and (ii) bromine water, if it is decolorized from orange to colourless, then unsaturated alkenes were formed.

This is another example of over water, or displacement of water collection.

The dreschel bottle is to collect any sucked back water if the hot gasses cool and contract. Cold water on the hot Pyrex tube has very nasty effect! plus the risk of fire!

TOP OF PAGE and INDEXES

gas preparations for AQA AS chemistry, gas preparations for Edexcel A level AS chemistry, gas preparations for A level OCR AS chemistry A, gas preparations for OCR Salters AS chemistry B, gas preparations for AQA A level chemistry, gas preparations for A level Edexcel A level chemistry, gas preparations for OCR A level chemistry A, gas preparations for A level OCR Salters A level chemistry B gas preparations for US Honours grade 11 grade 12 gas preparations for pre-university chemistry courses pre-university A level revision notes for gas preparations  A level guide notes on gas preparations for schools colleges academies science course tutors images pictures diagrams for gas preparations A level chemistry revision notes on gas preparations for revising module topics notes to help on understanding of gas preparations university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 11 grade 11 AQA A level chemistry notes on gas preparations Edexcel A level chemistry notes on gas preparations for OCR A level chemistry notes WJEC A level chemistry notes on gas preparations CCEA/CEA A level chemistry notes on gas preparations for university entrance examinations how do you prepare ammonia gas, what apparatus and chemicals do you need to make ammonia? how do you collect a sample of ammonia? how do you prepare carbon dioxide gas? what apparatus and chemicals do you need to make carbon dioxide gas? how do you collect a sample of carbon dioxide? describe an experiment on cracking hydrocarbon alkanes to make alkenes how do you prepare chlorine gas? what apparatus and chemicals do you need to make chlorine gas? how do you collect a sample of chlorine? what methods are there for drying gases? how do you prepare hydrogen gas? what apparatus and chemicals do you need to make hydrogen gas? how do you collect a sample of hydrogen? how do you prepare hydrogen chloride gas? what apparatus and chemicals do you need to make hydrogen chloride gas? how do you collect a sample of hydrogen chloride? how do you prepare nitrogen dioxide gas? what apparatus and chemicals do you need to make nitrogen dioxide gas?  how do you prepare oxygen gas? what apparatus and chemicals do you need to make oxygen gas?  how do you collect a sample of oxygen? how do you prepare sulfur dioxide gas? what apparatus and chemicals do you need to make sulfur dioxide gas? how do you collect a sample of sulfur dioxide diagrams of apparatus to make the gases  ammonia, carbon dioxide, chlorine, hydrogen, hydrogen chloride, nitrogen dioxide, oxygen and sulfur dioxide GCSE chemistry IGCSE chemistry revision notes on methods of preparing gases KS4 GCSE Science revision notes on methods of preparing gases GCSE chemistry guide notes on methods of preparing gases for schools colleges academies science course tutors images pictures diagrams for methods of preparing gases science chemistry revision notes on methods of preparing gases for revising chemistry module topics notes to help on understanding of methods of preparing gases university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 8 grade 9 grade10 AQA chemistry science GCSE notes on methods of preparing gases Edexcel chemistry science notes on methods of preparing gases for OCR 21st century chemistry science notes on methods of preparing gases OCR GCSE Gateway science chemistry notes on methods of preparing gases WJEC gcse science chemistry notes on methods of preparing gases CCEA/CEA gcse chemistry notes science O level chemistry notes for methods of preparing gases IGCSE chemistry revision notes on methods of preparing gases O level chemistry notes gcse chemistry revision free detailed notes on apparatus for preparing gases to help revise igcse chemistry igcse chemistry revision notes on apparatus for preparing gases O level chemistry revision free detailed notes on apparatus for preparing gases to help revise gcse chemistry free detailed notes on apparatus for preparing gases to help revise O level chemistry free online website to help revise apparatus for preparing gases for gcse chemistry  free online website to help revise apparatus for preparing gases for igcse chemistry free online website to help revise O level apparatus for preparing gases chemistry how to succeed in questions on apparatus for preparing gases for gcse chemistry how to succeed at igcse chemistry how to succeed at O level chemistry a good website for free questions on apparatus for preparing gases to help to pass gcse chemistry questions on apparatus for preparing gases a good website for free help to pass igcse chemistry with revision notes on apparatus for preparing gases a good website for free help to pass O level chemistry Methods of preparing gases apparatus gas collection methods reagents chemicals for preparing ammonia carbon dioxide chlorine hydrogen hydrogen chloride nitrogen dioxide oxygen sulfur dioxide gases preparations Equations

TOP OF PAGE - INDEX

[SEARCH BOX]

TOP OF PAGE and INDEXES