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Why Does Sodium Chloride Dissolve in Water?

Sodium chloride is also called the common salt. The ionic compound has a chemical formula as NaCl which consists of 1:1 ratio of sodium and chloride ions having molar mass of 22.99 and 35.45g/mol respectively. Every 100 g of NaCl constitute to 39.34 g of Na and 60.66g Cl. Here are some examples:

Sodium chloride is salt which is responsible for the salinity of sea water and extracellular fluid of many organisms. Because of this, NaCl is variedly used as a food preservative and in food in day to day life in order to add taste.  Apart from this, sodium chloride is also used for de-icing of ice in order to have smooth movement of traffic during extreme harsh snowy days.

 

Figure 1: Crystal structure of sodium chloride (Na Cl)

Water:

Water has a chemical formula – H2O.

Why does sodium chloride dissolve more in water?

The water is polar, as the matter of fact; water is extremely polar which implies that water molecule has an asymmetrical arrangement of positive and negative charge that forms polar bonds. The water is made from two atoms of hydrogen and one atom of oxygen. The atomic bond between H2o are covalent that simply means that electrons are shared. Among which Hydrogen has positive charge and oxygen have negative charge.

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NaCl is made up of 1 atom of sodium and 1 atom of chloride in which Na is positively charged whereas Cl is negatively charged.

The positive hydrogen atom of water attracts the Negative Cl atom of NaCl and the negative oxygen atom attracts the positive Na. The attractive force between molecules dissociates the sodium chloride ions and hence the NaCl gets dissolved in water.

To understand the solubility of sodium chloride in water, let’s do an activity.

Things you need-

  1. Glass of water
  2. Sodium chloride( NaCl) or table salt
  3. Stirring pipe
  4. Alcohol (along with supervision)

Step 1: Take a glass of water, mix salt and stir well.

Step 2: Take a glass of water, mix alcohol and add salt. Stir it well.

See both the glass and what did you see?

The glass in which the salt is mixed, the mixture will be homogenous. If you would have stirred it well, the salt will be completely dissolved in the water. The reason for complete dissolving of NaCl is the polarity of water. The Na+ molecule of sodium chloride gets attracted towards OH. Same thing happened with Cl- ions as they got attracted towards H+ ions.

Let us now see what will happen with the other glass.

The glass in which the salt, alcohol and water is mixed, the salt would not be dissolved as it should be. The reason for salt to not dissolve in alcohol is because there was no polarity of alcohol that should be attracting sodium chloride molecules. Therefore, from the above activity, we learn about the reason and also see it happen, as to why sodium chloride gets dissolved in water.