In the lab you are given 4 bottles, each containing about 5 grams of finely powd

Question

In the lab you are given 4 bottles, each containing about 5 grams of finely powdered white substance. Located near the bottles are four labels which indicate that each bottle contains a high purity substance. One bottle contains glucose (C_6 H_12 O_6), another bottle sodium chloride (NaCl), another aluminum oxide (Al_2 O_3), and another zinc sulfate (ZnSO_4). Assume that these labels belong to the bottles and that each bottle contains a single substance. Describe the tests that you could conduct to determine which label belongs to which bottle. Give the results you would expect for each test. Make sure you justify each compound by using knowledge of solubility rules and net ionic equations. You may use only use a solution of barium nitrate, a conductivity tester and water to identity of the substance in each of the bottles.

Explanation / Answer

1) From solubility test with solvent water we can identify Al2O3. Because Al2O3 is insoluble in water and remaining three are soluble in water.

So the substance which is insoluble in water is Al2O3

2) ZnSO4 can be identified using barium nitrate. First all the remaining three salts are dissolved in water in different test tubes and barium nitrate solution is added to three test tubes. Only ZnSO4 gives white precipitate. Remaining two do not give precipitate.

ZnSO4(aq) + Ba(NO3)2(aq) -------> BaSO4(s) + Zn(NO3)2(aq)

Net ionic equation

SO4^2- (aq) + Ba^2+ (aq) ----------> BaSO4(s)

Hence ZnSO4 is identified with barium nitrate solution.

3) Once you identify above two compounds, you have sugar (glucose) and salt (NaCl).

You may identify by taste one (NaCl) is salty and another (glucose) is sweet.

Otherwise glucose can also identify using heating. Glucose give burnt sugar smell on heating. So using this test we can identify sugar.

4 ) remaining one is sodium chloride (NaCl)

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