Question

Name Date Experiment5 Identification of Unknowns: PRELAB 1. In this experiment you will do qualitative analyses to determine the identity of unknown compounds What oes 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 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 is added? above. What anion(s) do these compounds contain? Be sure to include the correct charge on the anion D. Suppose that you are working with a water-soluble unknown which does not produce a bright pink colored solution when phenolphthalein is added and does not give a precipitate when added to 1.0 M NaOH. Based on this result, which of the unknowns might you have? (list all possible identities) E. After getting the results of this NaOH test (no precipitate; part D), which test should you perform next to narrow down the list of possible identities for your unknown? 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? 3. 41

Answer 1

1.Qualitative analysis determines the elements or functional groups present in a substance .

Quantitative analysis- Measurement of the quantities of the particularconstituents present in a substance

2. A.calcium carbonate ,CO2 is released

B. Sodium carbonate and sodium bicarbonate they are the sources of carbonate ion which results in production of CO 2 gas

C.Na2CO3 and NaHCO3 .They contain carbonate anion ( CO3)^2-

D.It can be Fructose , Sucrose, Boric acid,sodium bicarbonate and sodium chloride

E.Benedict's reagent test either it forms Orange/Red precipitate or no precipitate at all

3.if the compound is used too much then no homogeneous solution is formed which is required for testing and there will be suspended particles