The test tubes contain: ammonium chloride, barium nitrate, barium carbonate, copper sulfate.

The test tubes contain: ammonium chloride, barium nitrate, barium carbonate, copper sulfate. Using these solutions, as well as hydrochloric acid and sodium hydroxide, determine in which test tube each of the substances is located. Write the reaction equation.

By the condition of the problem, we have 4 test tubes with substances. Prepare a solution from some of the salts. First of all, you should pay attention to the test tube with undissolved salt. Of the four substances presented, only one is insoluble in water – barium carbonate. To confirm the guess, let’s add hydrochloric acid to this test tube. As a result of the reaction, an unstable carbonic acid is formed, which decomposes into carbon dioxide and water. In the test tube, we will observe the corresponding “boiling”.

BaCO3 + 2 HCl = BaCl2 + H2CO3 (H2O + CO2)

There will be no visible change when acid is added to other tubes.

Another test tube will be of a strong color – presumably, it is copper sulfate. Let’s check it with alkali.

After adding sodium hydroxide to copper sulfate, a blue precipitate of copper hydroxide will precipitate.

CuSO4 + 2 NaOH = Cu (OH) 2 + Na2SO4

We also add sodium hydroxide solution to the solutions from the other two tubes.

In a test tube with ammonium chloride, when it reacts with alkali, ammonium hydroxide is formed, which decomposes into ammonia gas and water. Ammonia can be felt by the smell or by the blue discoloration of the wet litmus paper over the test tube.

NH4Cl + NaOH = NaCl + NH4OH (H2O + NH3)

We will not notice significant changes in a test tube with barium nitrate.

To confirm that the remaining substance is barium nitrate, add to its solution a little copper sulfate solution, which we have already identified earlier. The reaction will result in a white precipitate of barium sulfate.

CuSO4 + Ba (NO3) 2 = Cu (NO3) 2 + BaSO4