Post Lecture Homework Chapter 04 Percent Chromium in Steel Sample 7 of 11 A stai

Question

Post Lecture Homework Chapter 04 Percent Chromium in Steel Sample 7 of 11 A stainless steel alloy is to be analyzed for its chromium content. A 5.00 g sample of the steel is used to produce 250.0 mL of a solution containing Cr2072A 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. Part A What is the percent Cr, by mass, in the steel sample? Express your answer numerically as a percentage View Available Hint(s) Submit Provide Feedback Next>

Explanation / Answer

BaCrO4 moles = mass / Molar mass of it = 0.145g / ( 253.37g/mol) = 0.000572mol

Cr moles = 0.000572 mol ( since 1BaCrO4 has 1Cr)

Now this isCr moles taken in 10ml of solution

initially we had 250 ml solution

Hence Cr moles present in 250 ml solution = 0.000572 x ( 250/10) = 0.0143

Cr mass = moles x molar mass of Cr = 0.0143 mol x 51.996g/mol = 0.74354 g

Mass % of Cr = ( 100 x Cr mass) / ( sample mass) = 100 x 0.74354g / 5g = 14.9

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