1. In this experiment you will do qualitative analyses to determine the identity

Question

1. In this experiment you will do qualitative analyses to determine the identity of unknown compounds.
What does qualitative analysis mean?

What does quantitative analysis mean?

2. Use the flow chart to answer the following questions (A-E).
A. Which non-water-soluble compound produces bubbles of gas when vinegar is added?

B. Which two water-soluble compounds produce bubbles of gas when vinegar is added?
C. Carefully examine the chemical formulas of the three compounds you just named above.

What ion do all three have in common? Be sure to include the correct charge on the ion.

D. Suppose that you are working with a water-soluble unknown which does not produce a bright pink colored solution when phenolphthalein is added. Based on this result, which of the unknowns might you have? (list all possible identities)

E. After getting the results of this phenolphthalein test (no pink color; part D), which test should you perform next to narrow down the list of possible identities for your unknown?

3. It is very important not to use too much of the unknown compound when carrying out the water-solubility test. Suppose you are working with an unknown that is actually soluble in water: you take a sample of the unknown that is too large (larger than the amount specified in the experimental procedure) and add some water. What do you think will happen?

Explanation / Answer

1).Qualitative analysis, is a branch of chemistry that deals with the identifiction of elements or grouping of elements present in a sample. The techniques employed in qualitative analysis vary in complexity, depending on the nature of the sample. In some cases it is necessary only to verify the presence of certain elements or groups for which specific tests applicable directly to the sample (e.g., flame tests, spot tests) may be available. More often the sample is a complex mixture, and a systematic analysis must be made in order that all constitutents may be identified.There are two type of qualitative analysis: qualitative inorganic analysis and quantitative organic analysis... Quantitative analysis is the determination of absolute or relative abundance of one, several or all particular substances present in a sample..... 2).A). CaCO3 compound produces gas bubbles when vinegar is added..CaCO3 is not soluble in water..... B).Na2CO3 and NaHCO3 are water soluble compounds which produces gas bubbles when vinegar is added... C). All the three compounds which produces bubbles of gas when vinegar is added are carbonates... whether they are soluble or insoluble in water... The common ion is the carbonate ion... CO3^2-....... The charge on the carbonate ion is -2.... D). In water soluble unknown compounds, the compounds that does not produce a bright pink colored solution when phenolphtalein is added are NaCl, NaHCO3, sucrose, fructose, H3BO3, MgSO4..... E).After getting the results of the phenolphtalein test ( no pink color), the test that is done to narrow down the list of possibe identities for the unknown compoud is adding the 1.0M NaOH..... 3).If we take the compound larger than the amount specified in the experimental procedure, it will take a lot of time to dissolve...Many soluble compounds won't dissolve immediately upon adding water - they may require stirring for several minutes before they dissolve fully.

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