Atomic absorption spectroscopy was used to determine the amount of aluminum in a sample of sunscreen. A standard solution of 1.00 ng Al /L was prepared and measured seven times to determine the detection and quantitation limits of the spectrometer. The standard measurements were: 0.72, 0.97, 1.40 , 1.21 , 0.79 , 1.17 , and 1.08 ng Al /L. Calculate the detection and quantitation limits for this instrument. detection limit: ng/L quantitation limit: ng/L

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

thats how its supposed to be