%3Cp%20class%3D%22c1%22%3EA%20solution%20of%20ammonia%20has%20a%20measurable%20v
ID: 822226 • Letter: #
Question
%3Cp%20class%3D%22c1%22%3EA%20solution%20of%20ammonia%20has%20a%20measurable%20vapour%0Apressure%2C%20detectable%20as%20the%20characteristic%20%22ammonia%20smell%22%20of%20the%0Asolution.%20The%20dissolution%20of%20ammonia%20in%20water%20follows%20the%0Aequlibrium%3A%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3ENH3(g)%20%26lt%3B--%26gt%3B%20NH3(aq)%20%26nbsp%3B%26nbsp%3B%26nbsp%3B%0AK%3D57.5%20M%20atm-1%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3EUsing%20this%20and%20other%20K%20values%20you%20can%20find%20in%20your%0Atext%20(or%20online)%2C%20determine%20the%20vapour%20pressure%20(in%20atm)%20of%20ammonia%0Agas%20above%20an%20aqueous%20solution%20that%20is%20at%20pH%208.59%20and%20contains%0A0.0002219%20M%20of%20ammonium%20ion.%3C%2Fp%3E%0A%3Cp%20class%3D%22c1%22%3EHighlight%20below%20for%20hints%3A%3C%2Fp%3E%0A%3Cul%20class%3D%22c4%22%3E%0A%3Cli%3E%3Cspan%20class%3D%22c2%22%3EHow%20is%20ammonia%20related%20to%20the%20ammonium%20ion%3F%0AWhat%20is%20the%20K%20of%20this%20equilibrium%3F%3C%2Fspan%3E%3C%2Fli%3E%0A%3Cli%3E%3Cspan%20class%3D%22c2%22%3EThe%20K%20for%20the%20equation%20shown%20in%20the%20question%0Ais%20in%20mixed%20units%20-%20it%20is%20neither%20a%20K%3Csub%3Ec%3C%2Fsub%3E%3Cspan%20class%3D%0A%22Apple-converted-space%22%3E%26nbsp%3B%3C%2Fspan%3Enor%20a%20K%3Csub%3EP%3C%2Fsub%3E.%20The%20units%0Agiven%20show%20you%20the%20units%20of%20the%20quantites%20in%20the%20equilibrium%0Aexpression.%26nbsp%3B%3C%2Fspan%3E%3C%2Fli%3E%0A%3Cli%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%22c2%22%3EYou%20know%20pH%20-%20what%20quantity%0Acan%20you%20calculate%20directly%20from%20this%20value%3F%20how%20can%20you%20relate%20it%0Ato%20the%20equilibria%20discussed%20in%20the%20points%20above%3F%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fli%3E%0A%3C%2Ful%3E%0A%3Cp%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%0A%22c2%22%3E--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fp%3E%0A%3Cp%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%22c2%22%3EI'm%20incredibly%20stuck%20on%20this%0Aquestion%2C%20the%20main%20part%20being%20which%20equations%20do%20I%20use%20and%20where%20do%0AI%20find%20the%20constants%20for%20them.%20I%20could%20not%20find%20any%20two%20equations%0Athat%20cancelled%20out%20in%20a%20way%20to%20yield%20the%20above%20equation.%20Also%20is%0Athe%20pH%20%2F%20ammonium%20ion%20given%20to%20me%20as%20the%20initial%20values%20or%20at%0Aequilibrium%20values%3F%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fp%3E%0A%3Cp%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%22c2%22%3EAny%20help%20on%20this%20question%0Awould%20be%20greatly%20appreciated%2C%20I've%20put%20in%20a%20solid%20hour%20and%20a%20half%0Aand%20not%20been%20able%20to%20move%20forward%20the%20equations%20that%20I%20have%20to%20find%0Ais%20definitely%20what%20is%20making%20this%20problem%20very%0Adifficult.%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fp%3E%0A%3Cp%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%22c2%22%3EThanks!%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fp%3E%0A%3Cp%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%3E%3Cbr%20%2F%3E%3C%2Fp%3E%0A%3Cp%3E%3Cspan%20class%3D%22c3%22%3E%3Cspan%20class%3D%22c2%22%3Eedit%3A%20changed%20image%20to%0Atext%3Cbr%20%2F%3E%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fp%3E%0AExplanation / Answer
AT the given temperature and physical conditions there exists an equilibrium between the ammonia in gaseous and aqueous phase
Here given K =57.5 M atm-1
From the equation NH3(G)-->NH3(AQ).one has to decide what K has given up on seeing the units and the equilibrium conditions
K =[NH3(AQ)]/pressure of NH3(g)
Moreover ammonia in aqueous solution exists as
NH3 +H2O-->NH4+ +OH- .(this is an equilibrium reaction :both forward and backward)DUE TO SLIGHTLY BASIC NATURE OF AMMONIA.
H2O-->H++OH- .(THIS IS AN EQUILIBRIUM REACTION :BOTH FORWARD AND BACKWARD).HERE OH- Concentration is increased by ammonia dissolving in water.since we Keq of water .from the given PH one can find out the concentration of OH-.
WHEN ONE MOLE AMMONIA DISSOLVES IT PRODUCES equal no.of NH4+ ions and OH- ions.from this one can find out the concentration of NH4+ ions.
SO When ammonia is dissolved in water all the three equilibrium reactions exists and all should be satisfied
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