# Question #a3ca9

##### 1 Answer

#### Explanation:

*Specific rotation* can be found from *observed rotation* by using the formula

#color(blue)([alpha]_(Lamda)^T = (alpha)/(l * c))# , where

Now, path length is usually expressed in *decimeters* and concentration for solutions in *grams per 100 mL*.

Another important thing to mention here is that you didn't specify the wavelength of light used,

So, start by converting the concentration from

#"0.120 g"/"30 mL" = "0.004 g/mL"#

#0.004"g"/(1color(red)(cancel(color(black)("mL")))) * (100color(red)(cancel(color(black)("mL"))))/"100 mL" = "0.4 g/100 mL"#

and

#5.0color(red)(cancel(color(black)("cm"))) * "1 dm"/(10color(red)(cancel(color(black)("cm")))) = "0.5 dm"#

This means that the specific rotation will be

#[alpha]_(Lamda)^T = (-0.132""^@)/("0.5 dm " * " 0.4 g/100 mL") = color(green)(-0.66""^@)#