Nitric acid is produced by reacting ammonia with oxygen. The word equation is:
ammonia + oxygen → water + nitric acid
Platinum is a catalyst in this reaction.

Describe the test for oxygen gas. Give the result if oxygen gas is present.

The test for oxygen gas is a classic chemical test. Oxygen is required for combustion (burning). If you take a wooden splint, light it, and then blow it out so it is still glowing red, this is called a "glowing splint". When this glowing splint is placed into a sample of gas containing a high concentration of oxygen, the increased oxygen level allows the splint to burst back into flame, i.e., it relights. This is a positive test for oxygen.