-
Categories
-
Pharmaceutical Intermediates
-
Active Pharmaceutical Ingredients
-
Food Additives
- Industrial Coatings
- Agrochemicals
- Dyes and Pigments
- Surfactant
- Flavors and Fragrances
- Chemical Reagents
- Catalyst and Auxiliary
- Natural Products
- Inorganic Chemistry
-
Organic Chemistry
-
Biochemical Engineering
- Analytical Chemistry
- Cosmetic Ingredient
-
Pharmaceutical Intermediates
Promotion
ECHEMI Mall
Wholesale
Weekly Price
Exhibition
News
-
Trade Service
11.
4.
1 Elemental substances of selenium and tellurium
There are several allotropes in both selenium and tellurium.
Selenium includes gray selenium, red selenium and amorphous selenium, among which gray selenium is the most stable
.
Selenium is a typical semiconductor, and its conductivity can increase thousands of times under light
Selenium and tellurium are toxic, their chemical properties similar to S, S but not as active
.
11.
4.
2 Compounds of Selenium and Phosphorus
1.
a hydride
Both H 2 Se and H 2 Te are colorless gases with extremely unpleasant odors, and both are more toxic than H2S
.
H 2 Se and H 2 Te are unstable, and the stability of the hydrides of these elements decreases in the order of H 2 O, H 2 S, H 2 Se, and H 2 Te
.
The standard free energy of formation of H 2 Se and H 2 Te are both positive
H 2 Se and H 2 Te was dissolved in water to form sulfuric acid and hydrogen hydrogen selenate, their acidic than H 2 S strong
.
Metal selenide and dilute compounds can generate H 2 Se and H 2 Te by hydrolyzing or reacting with dilute acid
.
2.
Dioxide and oxyacid
Both SeO 2 and TeO 2 are white solids, and both can be obtained by burning simple substances in air, or by burning hydrides in air
.
SeO 2 and TeO 2 are more oxidizing than SO 2 and are medium-strength oxidants.
They can oxidize H 2 S, HI, etc.
to form elemental S, I 2 and so on
.
When they encounter strong oxidants, they can also be oxidized to the highest price
SeO 2 is dissolved in water to generate selenite H 2 SeO 3 , H 2 SeO 3 is a weak dibasic acid (K Θ a 1 =2.
40×10 -3 , K Θ a2=5.
01×10 -9 )
.
TeO 2 is not soluble in water.
3.
Trioxide and oxyacid
SeO 3 is a white solid, which can easily absorb water to generate selenic acid H 2 SeO 4
.
TeO 3 is an orange solid, hardly soluble in water, dilute acid and dilute strong base, but soluble in strong base to form phosphate
.
TeO 3 +2KOH (concentrated)=K 2 TeO 4 +H 2 O
H 2 SeO 4 is similar to H 2 SO 4 , it is a strong dibasic acid, the first step is completely dissociated, and the second step is the dissociation constant K Θ a2=2.
2×10 -2
.
And H 6 TeO 6 is very acidic (K Θ a1=2.
The oxidizing order of oxyacids with the highest oxidation number is H 2 SeO 4 > H 6 TeO 6 > H 2 SO 4 , and H 2 SeO 4 can oxidize Cl -
.
