please only answer questions 18 and 19.

Q18. A beer sample spiked with 0.05ppm internal standard has a diacetyl peak area of 1497 and an I.S. peak area of 63 . What is the concentration of diacetyl in the beer? Q19. When is an internal standard needed in a calibration method? In a gas chromatography experiment, a standard solution containing 25ppm of diacetyl, represented by X, and 0.05ppm of internal standard 2,3-hexanedione, represented by S, give peak areas of Ax=330 and As=59 (areas in arbitrary units), respectively. The response factor or response ratio (F) can be calculated using the following equation and rearranging the equation to solve for F : [X]Ax=F([S)As) F must be determined by measuring known concentrations of both diacetyl and 2,3-hexanedione first, before you can use this equation to determine an unknown concentration of diacetyl. If a calibration curve is created, one must determine the signal from both the analyte and internal standard and plot the relative signal vs. the concentration of the analyte standard, as shown in the data in Table 2. Table 2. Signal collected for 2,3-butanedione samples spiked with a 2,3-hexanedione internal standard. Q14. Calculate the signal ratio for each standard and fill in the results in the empty columns of Table 2. Calculate F for the 25 and 50ppm standards. Are the F values similar/different? Q15. If you want to construct a calibration curve for diacetyl incorporating the internal standard, what should be plotted on each axis? Consider the equation above that we used for the response factor