Lab Midterm Flashcards
What is the difference between a coordination compound and a complex?
A coordination compound is the complex with its neutralizing ion; the complex has a charge
What is a monodentate ligand and give examples
A ligand that forms one bond; Water, NH3, SCN-, S2O32-, F-, Cl-, Br-, I-, OH-
What is a bidentate ligand and give examples
A ligand that forms two bonds; ethylenediamine (en), oxalate, mercaptol, tartrate ion
What is polydentate ligand and give examples
Ligands that form more than one bond; ethylenediaminetetraacetate ion (Y4-, 6 bonds), diethylenetriamine (3), Tripolyphosphate ion (5)
Define chelating agent (aka sequestering agent)
Ligands that form two or more bonds to a transition metal ion
Define coordination number
The number of bonds between a metal ion and its ligands
What is LeChatelier’s Principle?
If an external stress (change in concentration, temperature, etc.) is applied to a system in a state of dynamic equilibrium, the equilibrium shifts in the direction that minimizes the effect of that stress.
What is a buffer? Give an example
A buffer resists pH change; consists of a weak acid and its conjugate base or a weak base and its conjugate acid; e.g. acetic acid CH3COOH
What is the common-ion effect?
The effect of adding an ion or ions common to those already present in a system at a state of dynamic equilibrium
What is array analysis? What are the pros and cons?
To each individual anion, we added reagent and observed whether a chemical reaction takes place (ppt, color change, gas, heat). The approach is fast, but not useful for mixture of ions
What type of reaction occurs between Fe3+ and the halides (Br-, I-, Cl-)?
Redox
What is a way to test for nitrate in solution? (NO3-)
Brown Ring Test
What method was used for Qual I Cations? (Na+, K+, NH4+, Mg2+, Ca2+, Cu2+). What is a negative about this method?
Divide and conquer; it is time consuming
What was the procedure for Qual I Cations? (Na+, K+, NH4+, Mg2+, Ca2+, Cu2+)
Mixture of cations -> add group reagent -> separate them into groups -> divide and conquer (separate ions) -> need flow chart
Why use a flame test for Na+ and K+?
Na+ and K+ are soluble and cannot be detected by other techniques (acid-base, redox)
How do you test for NH4+?
Increase the pH of the solution using NaOH to generate NH3 gas. NH3 is a weak base and can be tested with litmus paper
Why did we add oxalate (C2O4) and CO3 to the Qual I cations?
The addition of oxalate and CO3 precipitates out other ions so that you can test for Na+ and K+
Qual I: Why not use NaOH instead of NH3?
Because NaOH is a very strong base and NH3 is a weak base, so if NaOH was used it would be outside of the desired pH range
Qual I: Why add HNO3 to Cu (s)?
To put Cu back in solution as Cu2+ and carry on the test
Define amphoteric and give an example
A substance that can act as an acid and a base; Al(OH)3
List the cations that form soluble salts and insoluble salts with OH-
Soluble: NH4+, Sr2+, Ba2+, Group 1A
Insoluble: Most cations
List the cations that form soluble salts and insoluble salts with CO3 2-
Soluble: NH4+, Group 1A (except Li+)
Insoluble: Most cations
List the cations that form soluble salts and insoluble salts with Cl-
Soluble: Most cations
Insoluble: Ag+, Hg2 2+, Pb2+, Cu+, Tl+
List the cations that form soluble salts and insoluble salts with I-
Soluble: Most cations
Insoluble: None
