Give the name and formula of one compound in each of the following : A. Hydrated substance B. Anhydrous substance C. Liquid drying agent D. Basic drying agent
Answers
Answer:
1A.You then add the word "hydrate" to the prefix to give the complete hydrate name. For the formula given above, it's hydrate name is calcium chloride dihydrate. The prefix "di" is used because it has two water molecules.
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What Is the Hydrate Chemistry Naming System?
Number of H20 molecules Prefix
10 deca-
2A.A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water, therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achieve perfect dryness; anhydrous compounds gradually absorb water from the atmosphere so they must be stored carefully.Table salt is anhydrous sodium chloride (NaCl). Gaseous HCl is anhydrous, which differentiates it from hydrochloric acid, a solution of 37 percent HCl in water (w/w). Heating copper(II) sulfate pentahydrate (CuSO4·5H2O) yields anhydrous copper(II) sulfate (CuSO4).
3A,Drying agents (also called desiccants) come in various forms and have found widespread use in the foods, pharmaceuticals, packing, electronics and many manufacturing industries.
Commonly used drying agents in organic laboratories are calcium chloride (CaCl2), sodium sulfate (Na2SO4) calcium sulfate (CaSO4, also known as Drierite) and magnesium sulfate (MgSO4), all in their anhydrous form
Their efficiency is measured by intensity, capacity and velocity can greatly vary from one solvent to the other.
1. Calcium chloride (n=6, e=1.5 mg/L) is a very good drying agent for a broad variety of solvents but is generally not compatible with hydroxy (alcohol, phenol), amino (amine, amide) and carbonyl (acid, ketone, ester) functions due to basic impurities such as Ca(OH)2 and CaCl(OH). In addition, it tends to form adducts with some of those compounds as well. It is often used in drying tubes because it also is available in granular form.
2. Calcium sulfate (n=0.5, e=0.004 mg/L) is a neutral and good drying agent. However, it does not have a high capacity, which makes it useless for very wet solutions. The commercially available Drierite® contains about 2 % cobalt chloride as indicator, which can be leached out into various solvents i.e. ethanol, DMSO, DMF, ethers, etc. Drierite is often used in desiccators. If the compound is pink, the water can be removed by heating the compound to 210 oC for an hour.
Drierite
Dry (blue) Wet (wet)
3. Magnesium sulfate (n=7, e=2.8 mg/L) is a slightly acidic drying agent. It works well in solvents like diethyl ether, but not as well for ethyl acetate. It is a fast drying agent, in part because it comes as a fine powder with a large surface area.
4. Sodium sulfate (n=10, e=25 mg/L) has a very high capacity and is mainly used for very wet solutions. It is very efficient in ethereal solutions, but it also absorbs other polar compounds like alcohols, etc. In addition, it is slower compared to magnesium sulfate, etc.
5. Potassium hydroxide (KOH, n= high, e=0.1 mg/L) and potassium carbonate (K2CO3, n=2, e=moderate) are both of basic nature and often used to dry basic solutions containing amines. They cannot be used to dry acidic compounds since they react with them.
6. Sulfuric acid (H2SO4, e=0.003 mg/L) and phosphorous pentoxide (P4O10) are both acidic drying agents that are mainly used in desiccators and not in direct contact with the solution since they are very aggressive reagents. Both have a very high capacity. Sulfuric acid forms hydrates while phosphorous pentoxide is ultimately converted into phosphoric acid.
P4O10 + 6 H2O ----- > 4 H3PO4
7. Molecular sieves are alumino silicates with a three-dimensional network with different pore sizes (3-5 Å). They have to be activated prior use and also can be regenerated at higher temperatures (~180 oC - 260 oC, 1-2 hours).
______________table_____________________________
Class of Compounds Recommended Drying Agent
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Alkane, alkyl halides MgSO4, CaCl2, CaSO4, H2SO4, P4O10
Aromatic hydrocarbons, ethers MgSO4, CaCl2, CaSO4, P4O10, Na-metal
Aldehydes, ketones, esters Na2SO4, MgSO4, K2CO3, CaSO4
Alcohols MgSO4, K2CO3, CaSO4, CaO, BaO
Amines KOH, K2CO3
Acidic compounds Na2SO4, MgSO4, CaSO4
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Explanation:
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