Sugars dissolving

First we can investigate, qualitatively, the extent to which the solids dissolve in the liquids. By adding a small piece of each solid to a milliliter of liquid, we easily discover that sugar dissolves both in water and ethyl alcohol, sodium chloride dissolves readily in water but not in ethyl alcohol, and iodine does not dissolve much... 

Thus we find great variation among solutions. Iodine dissolves in ethyl alcohol, coloring the liquid brown, but does not dissolve readily in water. Sodium chloride does not dissolve readily in ethyl alcohol but does dissolve in water, forming a solution that conducts electric current. Sugar dissolves readily both in ethyl alcohol and in water, but neither solution conducts electric current. These differences are very important to the chemist, and variations in electrical conductivity are among the most important. We shall investigate electrical conductivity further but, first, we need to explore the electrical nature of matter. 

Sugar dissolves in water, but the resulting solution conducts electric current no better than does pure water. We conclude that when sugar dissolves, no charged particles result no ions are formed. Sugar must be quite different from sodium chloride. 

In view of the discussion of the factors that determine the rate of dissolving (Section 10-1.2), propose two methods for increasing the rate at which sugar dissolves in water. 

Sugar dissolves In water to give a solution that contains individual sugar molecules distributed uniformly among the water molecules. The aqueous sugar solution is stable and remains uniform indefinitely. Recall from Chapter 1 that a solution is a homogeneous mixture. On the microscopic scale, one microscopic portion of a solution looks the same as every other microscopic portion. 

Sugar dissolving in coffee involves dispersal of molecules. Sugar molecules are distributed more widely in solution than they are in the solid crystal. 

Does sugar dissolve faster in hot coffee or in lukewarm coffee Explain. 

Does lump sugar or granular sugar dissolve faster in water, all other factors being equal Explain. 

Ans. Granular sugar dissolves faster it has more surface area in contact with the liquid. 

Sugar should be more soluble in ethanol than in octanol. Like dissolves like. Chemists know from experience that sugar dissolves well in water. Therefore, you expect sugar to dissolve best in solvents that are most similar to water. Because ethanol is more miscible with water than is octanol, you expect that ethanol has solvent properties (especially polarity) more like water than octanol does. 

Preparation of Lead(Il) Acetate (Lead Sugar). Dissolve 3 g of lead(II) oxide in a calculated amount of a hot 50% acetic acid solution. Filter the solution, and add 1 ml of acetic acid with the same concentration to the filtrate. Evaporate the latter up to half of its initial volume and let it stand for crystallization. Separate the crystals from the mother liquor on a Buchner funnel and wash them with small portions of ethanol, and then with ether (for what purpose ), What is the composition of the product ... 

Homogeneous means that the mixture has the same composition everywhere. When sugar dissolves in water, the mixture is homogeneous. A mixture that is not the same everywhere (such as orange juice, which has suspended solids) is heterogeneous. 

To tell whether a sugar solution is saturated or not, add more sugar and see if it will dissolve. If the sugar dissolves, the solution was not saturated. Alternatively, cool the solution and see if any sugar precipitates. If it precipitates, then the solution was saturated. Because sugar forms supersaturated solutions so easily, however, neither of these methods is always successful. 

Figure 3-3 Separation of oligosaccharides by gel filtration. The sugars dissolved in distilled water were passed through a column of Sephadex G-25. The peaks contain (right to left) glucose, cellobiose, cellotriose, etc. From Flodin and Aspberg.64...

Put one cup of hot tap water in the two-cup measuring cup. Add one-half cup of sugar to the hot water. Stir the water with a spoon until the sugar dissolves. You can no longer see the sugar when it dissolves. 

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