Complex Ions and Precipitation Reactions

Complex Ions and Precipitation Reactions Among the most common reactions in the qualitative analysis are those involving the formation or decomposition of complex ions and precipitation reactions. These reactions may be performed directly by adding the appropriate anion, or a reagent such as H2S or NH3 may dissociate in water to furnish the anion. Strong acid may be used to dissolve precipitates containing a basic anion. Ammonia or sodium hydroxide may be used to bring a solid into solution if the cation in the precipitate forms a stable complex with NH3 or OH-. A cation is usually present as a single principal species, which may be a complex ion, free ion, or precipitate. If the reaction goes to completion the principal species is a complex ion. The precipitate is the principal species if most of the precipitate remains undissolved. If a cation forms a stable complex, the addition of a complexing agent at 1 M or greater generally will convert the free ion to complex ion. The dissociation constant Kd can be used to determine the extent to which a cation is converted to a complex ion. The solubility product constant Ksp can be used to determine the fraction of cation remaining in a solution after precipitation. Kd and Ksp are both required to calculate the equilibrium constant for dissolving a precipitate in a complexing agent. Complexes of Cations with NH3 and OH- Cation NH3 Complex OH- Complex Ag+ Ag(NH3)2+ Al3+ Al(OH)4- Cd2+ Cd(NH3)42+ Cu2+ Cu(NH3)42+ (blue) Ni2+ Ni(NH3)62+ (blue) Pb2+ Pb(OH)3- Sb3+ Sb(OH)4- Sn4+ Sn(OH)62- Zn2+ Zn(NH3)42+ Zn(OH)42-

All About the Major French Verb Faire

All About the Major French Verb Faire The irregular verb faire  (to do or to make)  is one of the 10 most frequently used verbs in the French language alongside à ªtre,  avoir, dire, aller, voir, savoir, pouvoir, falloir, and vouloir. Faire is also used to form  the causative construction and in numerous idiomatic expressions. 'To Do' or 'To Make' Faire means to do and to make in most senses that these verbs are used in English. Je fais la lessive:  Im doing the laundry.Je fais mes devoirs: Im doing my homework.Je fais du bricolage: I do odd jobs/DIY projects.Je fais un gà ¢teau: Im making a cake.Je fais des projets: Im making plans.Je fais des progrà ¨s: Im making progress. Exceptions When the intent is to communicate to make, the French tend to be more specific, and, instead of faire, they would use, for example, fabriquer, construire, obliger, forcer, donner,  or a whole list of alternate verbs. In the following instances, idiomatic usage calls for  the verbs rendre and prendre, not faire: When to make is followed by an adjective, it is translated by rendre: Ça me rend heureux: That makes me happy. To make a decision is expressed with  prendre une dà ©cision: Jai pris une dà ©cision: I made a decision. Causative Construction The  causative  construction  faire  plus an infinitive describes when someone or something has something done, makes someone do something, or causes something to happen. Je fais laver la voiture: Im having the car washed.Il ma fait laver la voiture: He made me wash the car.Le froid fait geler leau: Cold makes water freeze. Expressions With 'Faire' Faire is used in a number of idiomatic expressions, including many related to weather, sports, math, and everyday life. Il fait du soleil: Its sunnyIl fait froid:  Its cold out.il fait beau/il  fait beau temps:  Its nice weather./Its nice out./The weather is fine/nice.Je fais du ski: I ski.Je fais du golf: I golf.Deux et deux font quatre: Two plus two equals (makes) four.Je fais de lautostop:  Im hitchhiking.Il fait sa tà ªte:  He acts impulsively.Ça fait parti de notre projet:  Thats part of our plan.faire 5 kilomà ¨tres:  to go 5 kilometersfaire trois heures: to be on the road for three hoursfaire acte de prà ©sence:  to put in an appearancefaire attention :  to pay attention to, watch out forfaire bon accueil:  to welcomefaire de la peine quelquun:  to hurt someone (emotionally or morally)faire de la photographie:  to do photography as a hobbyfaire des chà ¢teaux en Espagne:  to build castles in the airfaire des cours:  to give classes, lecturesfaire des à ©conomies:  to save up/to save money/to economizefaire de son mieux:  to do ones bestfaire du lard  (familiar): to sit around doing nothingfaire du sport:  to play sports faire du thà ©Ãƒ ¢tre:  to be an actor/to do some actingfaire du violon, piano:  to study violin, pianofaire dune pierre deux coups:  to kill two birds with one stonefaire face :  to oppose/to face up tofaire fi:  to scornfaire jour, nuit:  to be daytime, nighttimefaire la bà ªte:  to act like a foolfaire la bise, le bisou:  to kiss hellofaire la connaissance de:  to meet (for the first time)faire le mà ©nage:  to do housework Conjugations You will find  all tenses  of  faire  conjugated elsewhere; for now, here is the present tense to illustrate just how irregular this essential French verb is. Present tense je faistu faisil faitnous faisonsvous faitesils font