(a) the only information about the precision of the method is the precision for the three data.  (b) on the basis of long experience with the method, it is believed that s---->σ lindane.  (c) If s=0.28 is good estimate of σ, how many replicate measurement should be made in order for the mean for the analysis of sample to be within 0.2% of the true mean 90% of the time.

select the Ksp expressions that correctly match the corresponding compounds. a) silver sulfide: Ksp=[Ag^+]^2[S^2-] b) iron(III)sulfide:Ksp= [Fe^+3][S^2-] c) chromium (II) phosphate: Ksp= [Cr^+2]^2[PO4^2-] d) Silver sulfate: Ksp=[Ag^+]^2[SO3^2-]

A certain drug has a half-Iife in the body of 2.5 h. What should the interval between doses be, if the concentration of drug in the body should not fall belc 40.% of its initial concentration? Round your answer to 2 significant digits.

0.0123 g of the powder from the tablet ( 1.4770g) was  transferred to a 100 mL volumetric flask. 20 mL of 1M hydrochloric acid was added to the flask. The volume in the flask was then made up to the mark with deionized water which was filtered. 40 mL of the filtrate and 4 mL of a lanthanum chloride solution were placed into a large test tube. Half of the prepared sample was  spiked with a 20 mg/L calcium standard. The calibration standards and the unknown sample solutions were then measured for calcium concentration at 422.7 nm with flame atomic absorption spectroscopy.  Each tablet is stated by the manufacturer to contain 500 mg of calcium.   Sample ID         Absorbance Blank                 0.039Reagent Blank   0.194Sample              0.855Spiked sample   1.184Calibration curve: y = 0.0184x + 0.007; r2 = 0.991   Calculate the spike recovery for the calcium analysis.