Experiment 38 Pre-Laboratory Assignment
Qual I. Na+, K+, NH +, Mg2+, Ca2+, Cu2+
Date:____________, Lab Sec:__________, Name:______________, Desk No:__________
1. Identify the Qualification (s) that are confirmed present in a reference solution by
the formation of a precipitate. Write the formula of the precipitates.
b. the color of a soluble complex ion. Write the formula of the complex ion
. c. the characteristic color of a flame test.
d. the evolution of a gas
Ammonium ion:
Gas evolved = ammonia.
Smell = extremely pungent odor
2. Identify the Qualification (s) that are confirmed present in a test solution as a result of a Brønsted acid –base reaction.
The qualification that is present is ammonium ion (NH*).
The reaction of evolved ammonia with HCI is a Bronsted acid-base reaction. Here, the gas evolved is ammonia, which is reacted with hi, resulting in the evolution of fumes. These fumes confirm the presence of an ammonium ion.
3. a. When operating a centrifuge, what is meant by the expression “balance the centrifuge”?
The term balance the centrifuge means that all holders in the centrifuge should have an almost equal mass placed in all the holders, i.e., no holder should be empty. If one or more holders are empty, leaving at least one holder filled, then the centrifuge is called “unbalanced “. An unbalanced centrifuge can destroy the rotor or even injure someone.
b. How full should a test tube (or centrifuge tube) be when placed into a centrifuge?
3/4th of the maximum volume should be in a test tube when placed into the centrifuge.
4. Identify the reagent that separates
a. NH + from Na+. Explain the chemistry of the separation.
The reagent used to separate ammonium ions and sodium ions is sodium hydroxide. Adding NaOH to the solution containing a mixture of these ions will result in the formation of ammonia, while the sodium ion will not react and remains unaltered.
b. Cu2+ from Ca2+. Explain the chemistry of the separation.
The reagent used to separate copper ion from calcium ion is (NH4)2cos. (in presence of nhoh + nh¡ci). The calcium ion precipitates out as calcium carbonate, while copper remains unreacted.
c. Cu2+ from Mg2+. Explain the chemistry of the separation.
An excess of ammonia solution is used to separate copper ions and magnesium ions. The excess of ammonia reacts with copper ions to give a soluble complex, which is blue in color, while magnesium ions remain unreacted.
5. Identify the reagent (and its concentration) that is used to confirm the presence of each of the following:
a. NH + 4 … NH4+(aq) + H-(aq) → NH3(g) + H2O(l) …..Ammonia Gas Smell
b. Cu2+ … Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s) …. Gives a blue/turquoise ppt
c. Ca2+ … Ca2+(aq) + 2OH-(aq) → Ca(OH)2(s) …. Gives a white precipitate
6. Refer to Dry Lab 4.D to address the following questions.
a. On a flow diagram indicates,______file/database_______.
b. On a flow diagram, means________input/output_______.
c. On a flow diagram, means __marks a flange coupling in a flow diagram__.