Why ammonia gas is colorless?
We know ammonia gas is colorless, but what is it that cause it to be colorless? I think it has something to do with electromagnetic wave but not very sure about it, and can't seen to find any information on the net. So, please help me!
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Ammonia is a colorless gas with a characteristic pungent smell similar to human urine, as urine decomposes to release ammonia. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules; the liquid boils at -33.3 °C, and solidifies at -77.7 °C to a mass of white crystals. Liquid ammonia possesses strong ionizing powers (ε = 22), and solutions of salts in liquid ammonia have been much studied. Liquid ammonia has a very high standard enthalpy change of vaporization (23.35 kJ/mol, cf. water 40.65 kJ/mol, methane 8.19 kJ/mol, phosphine 14.6 kJ/mol) and can therefore be used in laboratories in non-insulated vessels at room temperature, even though it is well above its boiling point.
It is miscible with water. Ammonia in an aqueous solution can be expelled by boiling. The aqueous solution of ammonia is basic. The maximum concentration of ammonia in water (a saturated solution) has a density of 0.880 g /cm³ and is often known as '.880 Ammonia'. Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-air mixtures of 15-25% air. When mixed with oxygen, it burns with a pale yellowish-green flame. At high temperature and in the presence of a suitable catalyst, ammonia is decomposed into its constituent elements. Chlorine catches fire when passed into ammonia, forming nitrogen and hydrochloric acid; unless the ammonia is present in excess, then the highly explosive nitrogen trichloride (NCl3) is also formed.
The ammonia molecule readily undergoes nitrogen inversion at room temperature - that is, the nitrogen atom passes through the plane of symmetry of the three hydrogen atoms; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol in ammonia, and the resonance frequency is 23.79 GHz, corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed.
Gases, like other forms of matter, have physical properties such as color, odor, and taste. In general, gases tend to be colorless and odorless, although some important exceptions exist. Also, most gases are transparent: that is, it is possible to see objects through them rather clearly.
Ammonia is formed when nitrogen (N2) reacts with hydrogen (H2). Both nitrogen and hydrogen are colorless gasses when they react, the result, ammonia, keeps this property. Hope that helps!