A stainless steel alloy is to be analyzed for its chromium c

A stainless steel alloy is to be analyzed for its chromium content. A 6.70 g sample of the steel is used to produce 250.0 mL of a solution containing Cr2O72. A 10.0-mL portion of this solution is added to BaCl2(aq). When the pH of the solution is properly adjusted, 0.145 g BaCrO4(s) precipitates. What is the percent Cr, by mass, in the steel sample?

Solution

Solution:-

Moles of Cr in 10 ml of solution= moles of BaCr4

=mass/molar mass of BaCr4

=0.145g/253.32= 0.0005724 mol

Moles of Cr in sample= moles of cr in 250 ml of solution

=250/10*moles of cr in 10 ml of solution

=250/10*0.0005724

=0.01431 mol

Mass of Cr= moles * molar mass of Cr

=0.01431*51.966= 0.7436 g

Now

Mass percent of the Cr= mass of Cr/ Mass of samle*100

= (0.7741/6.70)*100

=11.55 %