A solution is prepared by dissolving $0\mathrm{.}1093$ grams of FD&C Red #$40$ in water to produce $2\mathrm{.}000$ Liters of solution. Given that the molecular formula of Red $40$ is $C_{18}{H}_{14}{N}_2{S}_2{O}_8,$ determine the molarity of this stock solution. $($Note: some sources will give a different formula for Red $40$; be sure to use this formula for your calculations$).$

$\frac{0\mathrm{.}1896}{450\mathrm{.}888}=\frac{0\mathrm{.}00042091428}{2\mathrm{.}000C}=0\mathrm{.}0002$ lors $714$

M

$2.25\mathrm{.}00mL$ of the dark red stock solution described question #$1$ is transferred to a volumetric flask and diluted with water to a total final volume of $200\mathrm{.}00mL.$

a$.$ how many moles of Red $40$ are in the $25\mathrm{.}00mL$ sample that was transferred?

moles

b$.$ After the dilution, what is the molarity of the Red $40$ in the $200\mathrm{.}00$ mL of solution?

M

note: the preceding problem $($ #$2$a and $b)$ is a dilution calculation. See the last part of the discussion section, just before the procedure, for a discussion of this calculation. We will be doing dilution calculations in almost every experiment in this course.

$3.$ The solution described in problem #$2$ is placed in the spectrophotometer. Based on the calibration curve shown on the next page, what would you predict the absorbance to be$?$ Note: like the example given in the discussion, the absorbance should be calculated, not just estimated from the graph. Notice that the slope and intercept of the calibration curve are provided in the figure on the next page.

Absorbance $=$