chemistry

Please rewrite the following.
Objective, introduction, materials, procedure (in the past tense).

Introduction:
Chemists are often required to determine the identity of unknown substances. One way to do this is by a method called qualitative analysis. Qualitative analysis determines the identity of a substance by carrying it through a series of chemical reactions. In contrast, quantitative analysis determines how much of a particular substance is present. Qualitative analysis requires a knowledge of the chemical behavior of the substances that the chemist suspects may be present in the sample so that they may be compared against the behavior of the unknown. If the unknown is a mixture of substances, it may be necessary to separate the contents based on differences in their solubility (see Experiment 1 in Part B of this manual).
In this experiment, you will first study the reactions of five different metal cations, each sup-plied as their nitrates (e.g., AgNO3), with four different reagents to learn about their chemical properties. For example, certain combinations may cause a color change in the solution or produce an insoluble precipitate. (Note that a solution that appears cloudy or milky indicates formation of a solid.) There may also be no observable change, which is equally as significant in describing the chemical behavior of a specific ion. You will also be given an unknown solu-tion that contains one of these metal ions. You can determine which cation it contains based on the knowledge you have acquired by investigating the reactions of the known cations.

The five metal cations are:
Mg21 (magnesium ion)
Ni21 (nickel (II) ion)
Cr31 (chromium (III) ion)
Zn21 (zinc ion)
Ag1 (silver ion)

The four reagents that you will combine with these cations are:
0.1 M hydrochloric acid
0.1 M sodium hydroxide
6 M sodium hydroxide
6 M ammonium hydroxide

You will observe several different types of chemical reactions in this experiment.
1. Double displacement reaction: Pb(NO3)2 (aq) + Na2SO4 (aq) PbSO4 (s) + 2 NaNO3 (aq)
Both reactants are clear, colorless solutions. An ion exchange occurs as the reactants are combined and insoluble lead (II) sulfate precipitates from solution.

2. Complex formation: Insoluble hydroxides of cations such as Co21, Cu21, Zn21, and Ni21 form soluble com-plexes in the presence of excess NH3 (provided as aqueous ammonia or NH4OH solution). For example, Cu21 ions form an insoluble hydroxide in dilute NH4OH, but the precipitate dissolves in excess aqueous ammonia.
(a) (b)
Cu21 (aq) + 2 OH2 (aq) Cu(OH)2 (s) limited
Cu(OH)2 (s) + 4 NH3 (aq) Cu(NH3)4 + 2 OH2 (aq)

3. Amphoterism: Some water-insoluble hydroxides are soluble not only in acids but also in sufficiently concentrated solutions of strong bases (such as NaOH). These hydroxides are defined as amphoteric, which means they exhibit both acidic and basic properties. Hydroxides of cations including Al3, Zn2, Pb2, and to a lesser extent Cu2 and Co2 display this behavior. These insoluble hydroxides dissolve in excess strong hydroxide by forming soluble complex ions.
(a) (b) Al31 (aq) + 3 OH2 (aq) Al(OH)3 (s) Al(OH)3 (s) + OH2 (aq) Al(OH)4 (aq).

Procedure:
This experiment will be carried out in a 24-well plate to allow simultaneous comparison of all results. The sample plate fits over the table on the next page to show each combination of cation and reagent. (The data sheet where you record your observations is a separate page.)
1. Select an unknown solution and record its number on the data sheet. 2. Place a clean 24-well plate over the table on the next page. 3. Add 10 drops of your unknown solution to each well across the first row of the plate.
4. Add 10 drops of each cation solution (metal nitrate solution) to each well across its cor-responding row of the plate.
5. Note the color of each cation solution and record it in the corresponding box in the first column of the data sheet.
6. Add 10 drops of each reagent solution to each well down its corresponding column of the plate.
7. Mix the contents of each well with a stirring rod. Be sure to rinse the rod with water after mixing each well.
8. Note the appearance of the contents of each well and record your observations in the cor-responding boxes of the data sheet. Consider the color (including colorless), as well as the formation of any precipitate in the solution (clear versus cloudy).
9. Identify the unknown cation by comparing the results for the unknown solution with the results for the known solutions.
You
5 minutes ago
So basically rewriting the information I put in instructions. Thanks

Last Completed Projects