Chemical Tests

Question 1

Test for ammonia gas

Answer 1

Turns litmus paper blue

Question 2

Test for water

Answer 2

Copper sulfate: white to blue

Cobalt chloride: light blue to pink

Question 3

How does the impurity in water affect the melting and boiling points?

Answer 3

Increases the boiling point and decreases the melting point

Question 4

Testing for cations with NaOH (general)

Answer 4

Dissolve the salt in distilled water. Add the salt solution and the NaOH solution in a test tube. Note the color of the precipitate formed

Question 5

Color for the precipitate of Fe+3 compounds in solution

Answer 5

Orange-brown

Question 6

Color for the precipitate of Fe+2 compounds in solution

Answer 6

Green

Question 7

What happens to the precipitate color of a Fe+2 solution upon standing

Answer 7

The green precipitate darkens on standing and turns orange-brown on the top of the tube due to oxidization

Question 8

Test for ammonium ions

Answer 8

React ammonium salt solution with NaOH solution to give off ammonia gas which turns litmus paper blue

Question 9

Test for carbonates

Answer 9

Add a little hydrochloric/nitric acid to a sample of carbonate salt (mostly solid). It fizzes: CO2 gas is given off which can then be tested

Question 10

Test for sulfates

Answer 10

Make a solution of the suspected sulfate salt in distilled water

Add dilute HCl acid to the salt to remove any other anions that may also produce a white precipitate when BaCl₂ is added

Add BaCl₂ solution which will produce a white precipitate of barium sulfate if the sample is a sulfate salt

Question 11

Test for halide ions

Answer 11

Make a solution of the suspected salt in distilled water

Add nitric acid to the solution

Add silver nitrate solution to produce a silver chloride/bromide/iodide solution

Question 12

What happens to silver chloride/bromide/iodide precipitates upon exposure to light

Answer 12

They turn grey or pale purple