In this demonstrate or class experiment, students watch an endothermic reaction between solid sign language barium hydroxide and also solid ammonium chloride. The reaction produce a liquid that evolves into ammonia gas, with a dramatic fall in temperature to about –20°C


Although the experiment can be safely brought out together a class experiment (with GCSE or A-level candidates in mind), that lasts only about 5 minutes and also may not be worth the extra time invested by students setting up and clearing away. Because of this it is recommended together being much more suitable as a teacher demonstration. Students can be allowed to feeling the outside of the very cold container.

You are watching: Barium hydroxide and ammonium chloride equation

Equipment

Apparatus

Eye defense (goggles)Beaker, 100 cm3Watch glassThermometer, analysis to –30°C (note 3)Top-pan balanceFume cabinet (optional)

Chemicals

Barium hydroxide-8-water (CORROSIVE), 32 gAmmonium chloride (HARMFUL), 10 gConcentrated hydrochloric mountain (CORROSIVE)Universal indicator (or litmus) paper, 1 strip

Health, safety and also technical notes

Wear eye protection (goggles) throughout.Work in a fume cupboard unless the room is fine ventilated.Consider using a thermocouple form thermometer which can be linked to a big display or computer system monitor.Barium hydroxide-8-water, Ba(OH)2.8H2O(s),(CORROSIVE) – check out CLEAPSS Hazcard HC010B. Prevent lumps as much as feasible when weighing the end the required amount.Ammonium chloride, NH4Cl(s),(HARMFUL) – watch CLEAPSS Hazcard HC009a.Avoid lumps as much as possible when weighing out the forced amount.Concentrated hydrochloric acid, HCl(aq),(CORROSIVE) – view CLEAPSS Hazcard HC047a. Use a tiny stock bottle to administer fumes because that the ammonia test.

Procdearteassociazione.orgre

Stand the manufacturer on a clock glass comprise a few drops that water, so the the base of the maker is poignant the water.Note the room temperature.Mix the 2 solids in the beaker and stir through the thermometer. The mixture i do not care slushy as a liquid is formed, together with a white suspension.The existence of ammonia deserve to be detected by smell, and also confirmed by blowing fumes indigenous the hydrochloric acid bottle across the beaker’s mouth and by using moist indicator paper.Observe the drop in temperature, i beg your pardon is evidenced by the reality that the maker freezes come the watch glass.

Teaching notes

It helps to use a large thermometer display. The cold beaker deserve to be passed about the course once the development of ammonia has actually stopped.

It is not possible to determine conveniently the specific barium compound or compounds produced in this reaction yet the equation is usually represented as:

Ba(OH)2.8H2O(s) + 2NH4Cl(s) → 2NH3(g) + 10H2O(l) + BaCl2(s)

or

Ba(OH)2.8H2O(s) + 2NH4Cl(s) → 2NH3(g) + 8H2O(l) + BaCl2.2H2O(s)

A-level students can be asked to calculate the value of the enthalpy and also entropy changes for the reaction, using conventional enthalpy alters of formation and standard entropy values obtained from a data publication or native the table below.

Compound

DHf⦵/ kJ mol-1

S⦵/ J mol-1 K-1

Ba(OH)2.8H2O(s)

-3345

427

NH4Cl(s)

-314

95

NH3(g)

-46

192

H2O(l)

-286

70

BaCl2(s)

-859

124

BaCl2.2H2O(s)

-1460

203

An enthalpy change of +164 kJ mol–1is acquired if the product is assumed to be BaCl2(s), and +135 kJ mol–1if that is suspect to be BaCl2.2H2O(s). Student should have the ability to predict qualitatively that the entropy adjust for the system has a positive value due to the fact that a gas and also a liquid are formed from 2 solids. From the values over they could additionally be asked to calculation the really entropy readjust for the system and also the surroundings, and also hence ∆Stotalor ∆G because that the reaction and confirm that the procdearteassociazione.orgre is spontaneous. A value of ∆Ssystemof +591 J mol–1K–1is derived if the product is suspect to be BaCl2(s) and +530 J mol–1K–1 if that is assumed to be BaCl2.2H2O(s).


Additional information

This is a resource from thePractical Chemistry project, occurred by the Nuffield foundation and the Royal society of Chemistry. This repertoire of over 200 practical tasks demonstrates a wide selection of chemistry concepts and processes. Each task contains considerable information for teachers and technicians, including full technical notes and also step-by-step procdearteassociazione.orgres. Valuable Chemistry tasks accompanyPractical PhysicsandPractical Biology.

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The experiment is also part of the Royal society of Chemistry’s continuing Professional advancement course:Chemistry for non-specialists.

Health and also safety checked, 2016


Specification

Republic the IrelandJunior CycleScienceChemical worldBuilding blocksEnergyLeaving CertificateChemistry5. Fuels and heats of reactions5.4 Exothermic and also Endothermic ReactionsActivitiesDepth the treatmentEnglandA/AS levelAQA ChemistryPhysical ChemistryThermodynamicsGibbs free-energy change, ΔG, and also entropy change, ΔSEdexcel ChemistryTopic13: Enegetics IITopic 13B: EntropyOCR Chemistry AModule 5: physical chemistry and transition elements5.2 Energy5.2.2 Enthalpy and entropyGCSEAQA Chemistry4.5 power changes4.5.1 Exothermic and endothermic reactions4.5.1.1 energy transfer throughout exothermic and endothermic reactionsAQA linked science: Synergy4.7 Movement and also interactions4.7.3 Acids and alkalis4.7.3.3 power changes and also reactionsAQA merged science: Trilogy5.5 power changes5.5.1 Exothermic and also endothermic reactions5.5.1.1 power transfer throughout exothermic and also endothermic reactionsEdexcel ChemistryTopic 7 - rates of reaction and energy changesHeat energy changes in chemistry reactionsEdexcel combined scienceTopic 7 - prices of reaction and also energy changesHeat energy changes in chemistry reactionsOCR Chemistry B: 21st centuryC1 Air and waterC1.2 Why are there temperature changes in chemical reactionsOCR combined science B: 21st CenturyC1 Air and also waterC1.2 Why room there temperature transforms in chemistry reactionsOCR merged science A: GatewayC3 chemical reactionsC3.2 EnergeticsOCR Chemistry A: GatewayC3 chemical reactionsC3.2 EnergeticsScotlandNational 5SQA ChemistryNature"s chemistryEnergy native fuelsEnergy indigenous fuelsNorthern IrelandGCSECCEA ChemistryUnit 2: more Chemical Reactions, Rates and Equilibrium, Calculations and also Organic Chemistry2.8 Energy changes in chemistryCCEA twin award scienceUnit C2: more Chemical Reactions, Rates and Equilibrium, Calculations and also Organic Chemistry2.8 Energy changes in chemistryA/AS levelCCEA ChemistryUnit A2 1: additional Physical and also Organic Chemistry4.2 Enthalpy, entropy, and free energy