stav 2010 question help

[depressedchild]

Salinity in soil is a serious problem across many areas in victoria. The sodium chloride in a 50.0g sample of soil was dissolved in deionised water, filtered then titivated with a solution of 0.4998 M silver nitrate. Using the titration data, the amount of sodium chloride in the soil sample was determined to be 1.58 percent by mass.

calculate a numerical value in ML, of the volume of silver nitrate used the in the titration and give your answer to the appropriate number of significant figures.

[AllAboutTheLGs]

50.0 x 0.0158 gives you the mass of NaCl in the soil sample.
using this, you can then find the amount (mol) of NaCl
Then by using c=n/v you can find out the volume.
Hope that helped

[Shenz0r]

You have to work backwards in this question as you're given the % by mass first.

1.58% = m(NaCl)/50 x 100
m(NaCl) = 0.79g
n(NaCl) = 0.79/58.5 = 0.0135 mol

AgNO_{3 (aq)} + NaCl _(aq) ----> AgCl _(aq) + NaNO_{3  (aq)}

n(AgNO₃) = 1/1 x n(NaCl) = 0.0135 mol

V(AgNO₃) = 0.0135/0.4498 = 0.0270 L = 27.0 mL (3 sf)