how can we finf the specific rotation of mixture of compounds like fructose and glucose if we don't knw its percentage composition in the mixture
To find the specific rotation of a mixture of compounds such as fructose and glucose, it is generally necessary to know their percentage composition in the mixture. However, in some cases, it may be possible to estimate the specific rotation using approximate values or by conducting experimental tests.
If you don't know the actual percentage composition of the mixture, one approach is to make an assumption about the approximate percentage composition based on the known properties or characteristics of the compounds. For example, if you know that fructose typically has a higher specific rotation than glucose, you could assume that the mixture contains more fructose than glucose.
Once you have an estimated percentage composition, you can use the specific rotation values of the individual compounds to calculate the average specific rotation of the mixture. This can be done using a simple weighted average formula:
Specific rotation of mixture = (Specific rotation of compound A * Percentage of compound A) + (Specific rotation of compound B * Percentage of compound B) + ...
In this case, compound A would represent fructose, compound B would represent glucose, and so on if more compounds are present in the mixture.
Alternatively, if it is not possible to estimate the composition or if more accuracy is required, experimental techniques can be used to measure the specific rotation of the mixture. This involves using a polarimeter, a device designed to measure the rotation of polarized light passed through a sample. Experimental methods can provide accurate results, but they require access to specialized equipment and expertise.
In summary, determining the specific rotation of a mixture of compounds like fructose and glucose without knowledge of their percentage composition can be challenging. Estimations based on known properties or experimental techniques are potential approaches to consider, but they may have limitations or require additional resources.