All of the chromium in a 0.750 gram sample of ore is converted to K_2CrO_4. The K_2CrO_4 is...


All of the chromium in a {eq}\rm 0.750 {/eq} gram sample of ore is converted to {eq}\rm K_2CrO_4 {/eq}. The {eq}\rm K_2CrO_4 {/eq} is dissolved in acid and the {eq}\rm CrO_4^{-2} (aq) {/eq} is titrated with a {eq}\rm 0.0200\ M {/eq} solution containing {eq}\rm Sn^{+2} {/eq} ions. The skeleton reaction is below.

{eq}\rm CrO_4^{-2} + Sn^{+2} \rightarrow Cr^{+2} + Sn^{+4} {/eq}

The lab technician finds that the {eq}\rm 0.750 {/eq} gram sample of ore requires {eq}\rm 13.75\ ml {/eq} of the {eq}\rm Sn^{+2}(aq) {/eq} solution to reach end-point. Complete and balance the reaction for the titration and determine the mass {eq}\% {/eq} of chromium in the ore.


The yield information can be known by understanding the molar relationship of the yield with reactants. The entire study can be done by using the balanced chemical equation.

Answer and Explanation: 1

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The given data is:

The mass of {eq}\rm K_2CrO_4 {/eq} ore is 0.750 g.

The concentration of {eq}\rm Sn^{2+} {/eq} is 0.0200 M.

The volume of...

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Chemical Calculation Problems for the AP Test


Chapter 14 / Lesson 3

Chemical calculations are expected in the multiple-choice section and the free-response section of the AP chemistry test. Learn more about the structure of the AP chemistry test and how to prepare for it with tips.

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