MediumChemistryHigh School (11–12)Coordination Compounds › Werner's Theory, Ligands and NomenclatureNumerical
Platinum(IV) forms the complex salt [Pt(NH₃)₄Cl₂]Cl₂…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Platinum(IV) forms the complex salt . A sample of of this salt is dissolved in water, and excess silver nitrate solution is added. Use these molar masses: Pt , N , H , Cl and AgCl . Find the molar mass of the salt, the amount of the salt, and the mass of silver chloride.
Need a reminder? The key ideaShow
Werner's theory: the primary valence is the oxidation state, and the secondary valence is the coordination number. The coordination sphere is the metal with its ligands, in square brackets. Only the counter ions outside the brackets are free in water, so only they give a precipitate with silver nitrate. A double salt gives all its ions. A complex keeps its complex ion.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. . Free chloride in one formula unit: 2.
Step 1. Molar mass. .
Step 2. Amount of the salt. .
Step 3. Amount of silver chloride. Each formula unit has 2 free chloride ions, so of . The two chloride ions inside the brackets give none.
Step 4. Mass. , which is .
Answer: , and of silver chloride.
Check. If all four chloride ions had given silver chloride, the mass would be twice as large. The coordination sphere holds half of them back.
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