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Altius FLE 1 Q35 Passage 6
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Naval_5457
#1 Posted : Sunday, July 12, 2020 2:24:19 AM
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In this passage the goal of the procedure is to reduce chromium. That would mean that chromium is gaining electrons. To reduce chromium wouldn't you need an oxidizing agent? I don't understand why the answer is B. I get that the passage states that for the reaction to occur you need acidic conditions which HCl would provide but HCl is an acid so it will accept electrons and so it is also a reducing agent not an oxidizing agent.
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INSTR_Molly_59
#2 Posted : Sunday, July 12, 2020 7:57:31 PM
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Hi Naval,

I'm on FLE 1 Q35 and its passage 7, and the correct answer is C, not B... Can you please let me know if FLE1 Q35 passage 6 Q35 is what you are looking at? Just want to make sure I really address your question properly :)
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Naval_5457
#3 Posted : Monday, July 13, 2020 4:09:53 AM
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Hi Molly,
I am looking at full length exam 1 covid version passage 6 question 35.
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INSTR_Katerina_102
#4 Posted : Monday, July 13, 2020 4:50:46 PM
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Hi Naval,

I see your point, this is a bit of a tricky question.

From the passage, we see that one method for removing Cr(VI) which is toxic is to convert it to a non-toxic oxidation state that is more easily precipitated by a metal hydroxide. This non-toxic oxidation state can be inferred to be Cr(III).

Now, this gets a bit tricky because you might think adding NaOH would precipitate the Cr(III), facilitating the removal of Cr, which is reasonable based on figure 1.

However, the question specifically asks you only to consider reactions 1 and 2, which show the conversion of Cr(VI) to Cr(III) under acidic conditions. For this type of question, you notice that you need a lot of acid to convert toxic Cr(VI) to Cr(III), so based on reactions 1 and 2 alone, it makes most sense to use more HCl as it it is acidic but does not oxidize Cr3+ back.

I hope this helps!
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