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The molecular mass of a chemical substance is determined by the weight of one mole. It mainly ranges between 18 and hundreds grams /mole for water and complex chemical compounds respectively. However it is believed that the lightest possible chemical is hydrogen gas, but no any set limit on how heavy a chemical compound can be. One can easily get the molecular (molar) mass of an element by simply looking at the atomic mass of that element on the periodic table. However this is different when we are dealing with chemical compounds such as sodium chloride (NaCl). Sodium chloride or table salt is used to add food flavor, but it is also used in the road de-icing process due to its low freezing point compared to water. The molecular mass of such chemical compounds are calculated by adding the molar masses of all atoms in a single molecule of that compound. For instance the molecular mass of NaCl should be equal to the molar mass of a unit atom of sodium plus the molar mass of a unit of chlorine atom (Shakhashiri, 1989). Mathematically this will be
(1 atom *23 grams/mole Na) + (1 atom *35.5 grams/mole Cl) = 58.5 grams/mole NaCl.
This formula is applicable to all other chemical compounds that you might think of. We can therefore clearly define the molecular mass or weight of a chemical substance as the mass of unit molecule of a substance (Dass, 2007).
Freezing Point Depression
The freezing-point depression phenomenon on the other hand is observed when a liquid or a solvent freezing point is depressed by an additional compound which has a lower freezing point than a pure solvent. It mainly occurs when a non-volatile solute is added to a pure solvent like water. The condition is commonly observed in the sea where the salty water tends to remain in liquid form even at temperature below zero degrees Celsius. Bearing in mind that this is the freezing point for pure water, saline solution will not solidify at that temperature as it has a lower freezing point (Fages, & Araki, 2005). Because of this reason, an ice bath containing salt is used to make ice cream or cool beers in many firms.
In some other cases people tend to use the saline solution freezing advantage for road salting in order to melt ice and snow on the highways. Road salting is effective in the removal of black ice which can at times be lethal and dangerous to drivers. However, according to the National Research Council (U.S.) Transportation Research Board, Nevada Dept. of Transportation., American Association of State Highway and Transportation Officials., & United States Federal Highway Administration (1996) road salting is only effective if the ambient temperature is not lower than -18°C.The reason being that below -18°C the saline solution will also be frozen. Salt was a rare commodity in the past but with industrialization there is an increased production.
Salt demand has however continued to rise over the time, and it is believed that approximately 51% of the world salt output is used by the cold countries. The salt in this case is used to de-ice roads during winter season. The majority of these nations however prefer to use calcium chloride to sodium chloride. This is because, calcium chloride is believed to generate some energy whenever it forms a solution with water and this energy heat up the ice or snow it comes into contact with. Calcium chloride also has a lower freezing point of -21°C compared to the -18°C in Sodium chloride. Calcium chloride is also said to be environmental friendly compared to sodium chloride (National Research Council (U.S.) Committee on the Comparative Costs of Rock Salt and Calcium Magnesium Acetate (CMA) for Highway Deicing, 1991). However it has a severe drawbacks when it comes to the de-icing of roads, as it promote corrosion of vehicles. It also requires special handling since it can severely cause damage to the human skin. On the other hand, sodium chloride is readily available all over the world and requires no special care when handling as it cannot harm individual unless in the extreme circumstances.
With the increasing infrastructure, salt is also used to add firmness to the soil under which highways are constructed. In the actual sense, salt minimizes the effect of shifting which is mainly caused by the humidity changes and heavy traffic load (Masterton, et al. 2011). In order to reduce the production cost of the road salt, firms tend to mix it with some byproducts such as the carbohydrate solution from the sugar processing. Such addition equally strengthens the salt rock making it more suitable to serve it purpose.
However there is side effect which comes as a result of using road salt. Among them includes the pollution of fresh water whenever the saline solution comes into contact with it. It can also harm or destroy the lives of the water plants and animals since it disrupts their osmoregulation ability. The increased saline in the sea water also create a huge problem as it causes the adhesion problem. At some point the naval authority and ship builders have to consider the salt concentration before constructing the seaport.
Additionally the road de-icing process is also associated with negative implications such as the corrosion of bridge decks, motor vehicles and other metallic components that may be used in the road construction. Its application also in most cases harms the environs and may harm the roadside vegetation as well as the local surface water (American Chemical Society, et al. 1998).
Various industries such as the oil and gas, textile, metal processing, rubber and leather tanning also requires salt concentrations in order to function effectively. It is therefore appropriate to say that the freezing depression of the saline solution is necessary in the daily running of our operations.
Molecular mass computation
The molar mass of a compound can also be termed as the weighted mean as it sums up sample combination of a substance. The equations which assist in molecular mass calculation are also referred to as the stoichiometric calculations (Ramsden, 2000). However there is always a probability of having an error in your computation. In order to counter this error, most of the molecular (molar) mass computations are done by multiplying the number of moles with the Avogadro’s constant. The molecular mass can therefore be defined as the sum of the individual isotopic masses of the atoms in a certain molecule. Because molecules are created by chemical reactions, there is insignificant possibility of creating some binding energies compared to the atoms at rest (Serdyuk, et al. 2007). You can also be able to measure the molecular mass of a compound using the mass spectrometry. In such a case the mass of a small molecule is usually reported as mono-isotopic. In order to convert the average molecular mass into molar mass, you ought to multiply it with the Avogadro’s constant which is approximated to be 6.022*10^23. The result is given as mass per unit of u (Johnson, et al. 2003).