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Experiments in General Chemistry,e placeholder.24190.edu. Printing is for personal, private use only. No part of this permission. Violators will be prosecuted. book may be re 3. How can the sodium tetraborate- water system be distinguished from a compound? Sadium tetra burate i a sdution 4. Describe your observations when an additional 2 grams of Na,B,O-10H,O is added to the solution. il ingduble with the sotvev 5iti nthe water what happens to the mixture in #4 when it is heated? 5, The neat increased 's 5otubitity cn 6. Describe what happens when the solution from #5 is allowed to cool. Are your observations consistent with your expectations? Explain your answer. ors.

Explanation / Answer

3. Sodium tetraborate is an ionic compound which when added into water separates into sodium cations and tetraborate anions and this chemical breaking of ionic bonds of the former in the latter is witnessed as dissolution. Thus, unlike a compound where the moieties are held together by strong forces by electron exchange, sodium tetraborate in water is a solution and not a compound.

4. In this scenario, the solution is made up of the solvent - water which dissolves the solute - borax. Therefore, when a large excess of solute is added it is the solute which stays undissolved or unionized in the saturated solution of borax in water and not the solvent (water) which is sitting insoluble in the solute as the substance that is dissolved is the solute while that being used to dissolve it is defined as the solvent. (Please correct solvent into solute in your answer)

5. Heat supplied externally helps the bonding forces that keep the solute molecule together as solid borax break by taking the thermal energy supplied helping it dissolve better.

6. Since the solution already saturated with borax was heated to further dissolve more quantities of borax, when the solution (called super-saturated) is cooled, it begins to precipitate out the excess solute put inside it. If the cooling is gradual, instead of a flaky or fluffy precipitation, a quite complex process of crystallization of the solute - borax occurs. It can be noted that the amount of borax precipitated is precisely the amount of borax that was left insoluble at room temperature as that much borax for that solvent quantity is soluble only at higher temperatures.

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