When 1.728 plusminus 0.001 g NaCl (58.443 plusminus 0.002 g mol^-1) is dissolved

Question

When 1.728 plusminus 0.001 g NaCl (58.443 plusminus 0.002 g mol^-1) is dissolved in a 250.0 plusminus 0.3 mL volumetric flask, what is the final concentration? 0.1183 plusminus 0 0002 M 0.118 plusminus 0.002 M 0.118 plusminus 0 001 M 0.1 plusminus 0.3 M An instrument displays the concentration of iron in sweet potatoes as 0.0032345 plusminus 0.0007849 wt%. How many significant figures in the concentration should the analyst report? 1 2 4 5 Which cuvette material should be used when analyzing HgCl_4^2-, which absorbs strongly at 230 nm? glass polycarbonate polystyrene quartz Which is not generally needed for atomic absorption spectroscopy? cuvette detector hollow cathode lamp monochromator What is the correct configuration for the UV-Vis absorbance instrument below? monochromator, source, sample, detector sample, monochromator, source, detector source, monochromator, sample, detector source, sample, monochromator, detector An unknown solution X absorbs at 378 nm. Given the information below, what is the concentration of unknown X? 0.214 mu M 0.224 mu M 2.14 mu M 2.24 mu M Beer's Law experiments arc generally performed at lambda_max because at this wavelength the sensitivity is highest. the concentration is proportional to absorbance. the absorbance value is independent of cuvette pathlength. the signal is free from interference by all absorbers. The transmittance of a 1.20 times 10^-4 M standard solution measured in a 1 00-cm cuvette was 0.350 What concentration of an unknown solution of the same substance with a transmittance of 0 631 in a l 00-cm cuvette? 6 86 times 10^-5 M 5.26 times 10^-5 M 3.79 times 10^-5 M 2.40 times 10^-5 M Which is not true regarding fluorescence measurements? fluorescence is generally more sensitive than absorbance. The duration of fluorescence is shorter than phosphorescence. The fluorescence intensity is proportional to the irradiance intensity. A fluorescence spectrum occurs at shorter wavelengths than its absorption spectrum. Compounds X and Y have the absorptivities given in the table A mixture of X and Y gives absorbance readings of 0.150 and 0.250 at 425 nm and 610 nm, respectively, in a 1.00-cm cuvette. What is the concentration of X in the mixture? [X] = 0.0852 mM [X] = 0.0891 mM [X] = 0.0906 mM [X] = 0.0929 mM

Explanation / Answer

Concentration= (moles of solute)/Volume of solution

Moles of solute= 1.728g/(58.443 g/mol) = 0.02956 mol

Volume= 0.25L
So, concentration= 0.02956/0.25= 0.118M

Calculate error, moles= o.001/0.002= 0.5 mole
Volume= 0.3ml/1000 = 0.0003

So error molarity= 0.5/0.0003 = 0.0016666 ~ 0.002M

Ans (B) = 0.118M+0.002M

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