Confusing Stoichiometry Question

  1. I got this question as an example question and I have no clue on how to solve part B

    Chlorine can be produced by the reaction:
    2KMnO4 + 16HCl ->2KCl + 2MnCl2 + 5Cl2 + 8H2O
    (a)What mass of KMnO4 is required to produce 2.5 L of Cl2 gas measured at STP?

    For part A I got 7.05 g ( 0.044615 moll)
    (b) Calculate the volume of commercial hydrochloric acid required (Commercial grade hydrochloric acid is 36.0% HCl by weight, and has a density of 1.18 g mL^(–1)).
     
  2. jcsd
  3. DrClaude

    DrClaude 1,974
    Science Advisor

    That is much too low. Please show your calculations.

    Can you start by figuring what mass of HCl you need?
     
  4. Borek

    Staff: Mentor

    I got 7.051 g as well:

     
    Last edited by a moderator: Sep 25, 2014
  5. DrClaude

    DrClaude 1,974
    Science Advisor

    I'm sorry for the mistake. I used the density of Cl2 given by WolframAlpha, which is much higher.
     
  6. Borek

    Staff: Mentor

    Looks like they are listing density of a liquid Cl2 - which doesn't make much sense at STP....
     
  7. DrClaude

    DrClaude 1,974
    Science Advisor

    Indeed. Very strange.

    I feel ashamed because I didn't follow the rule that I always tell my students: when you get a numerical answer, always try to figure out if the order of magnitude makes sense. I should've checked with the ideal gas law...
     
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