Question

calculate the % difference of the 0.5133g and 0.5275 g of struvite from the two water samples in question a. ----> two 10.0 Ml water samples were taking The procedure in this experiment is followed to determine the phosphate concentration. What would be the average phosphate concentration in the solution be( in units of molarity) if the student obtained 0.5133g and 0.5275g of struvite using gravimetric analysis? show all work assume this procedure precipitates out all of the phosphate from the sample in form of struvite

Answer 1

Struvvite is a phoshphate mineral having FORMULA NH4MgPO4.6H2O (Repeating units),

NH4MgPO4.6H2O = mol. wt= 245.40,

NH4MgPO4= mol. wt=137.31,

PO4= mol. wt= 94.97

the amount of struvite in gms after gravimetrric analysis are, 1=0.5133 gms and 2=0.5275 gms.,

this is the final wt of struvite without moisture , there fore we can calculate here first the moles of struvite obtained from 10.0 ml sample.

moles=mass in gms/mol.wt,

=0.5133/137.31=0.0037 moles of struvite ,

there fore one mole of struvite contains one mole of phoshphate, then for 0.0037 moles of struvite contains 0.0037 moles of phoshphate,

we can calculate the mass of phoshphate in 0.5133 gms of struvite,

=0.0037*mol. wt of phoshphate,

=0.0037*94.97=0.3550 gms of phoshphate,

if this is obtained from 10.0 ml sample then we cancalculate here the concentration of phoshphate in solution as,

= molarity=mass of solute*mol wt of solute/mass of solution*1000,

molarity=0.3550/94.97/10*1000 , (10 ml/1000 =0.01 L)

molarity=0.0037/10=0.000373*1000=0.373 M/L,

OR WEcan can calculate as,

molarity=moles of solute/volume in L

molarity=0.0037/0.01= 0.37 M/l,

2) we can calculate the gms of phoshphate present in 0.5275 gms as,

0.5275/137.37=0.003841 moles of struvite= 0.003841 moles of phoshphate,

phoshphate= 0.003841*94.97 =0.3648 gms of phoshphate,

molarity=moles of solute/volume in L

MOLARITY=0.003841/0.01 = 0.3841 M/LPHOSHPHATE    (10 ml/1000 =0.01 L),

average molar cncentration of phoshphate in struvite=0.37+0.3841=0.7541/2=0.3770 M/L PHOSHPHATE,

calculation of percentage difference of struvite as,

1) %=wt by volume=0.5133/10= 0.05133 %,

2) %=wt by volume=0.5275/10=0.05275 %,

difference=0.5133/0.5275=0.97.30*100=97.30 %,

0.5270 =100%,

0.5133=?,

by cross multiplying

0.5133*100=51.33/0.5275=97.31,

(100-97.31=2.69 %)