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Posted: **Sun May 22, 2022 11:51 pm**

: 4 A Student Mistakenly Added Concentrated 12m Hci To A Sample Of Unknown Instead Of Adding 6m Hci As Directed 1 1 (26.38 KiB) Viewed 13 times

: 4 A Student Mistakenly Added Concentrated 12m Hci To A Sample Of Unknown Instead Of Adding 6m Hci As Directed 1 2 (32.31 KiB) Viewed 13 times

4. A student mistakenly added concentrated (12M) HCI to a sample of unknown, instead of adding 6M HCI, as directed. (1) At first, a large amount of light-colored pre- cipitate formed, but some dissolved on further addi- tion of concentrated HCI. Write an equation(s) for the reaction(s) that might have occurred.

(2) The precipitate was separated from the supernatant liquid in (1) and was found to be insoluble in hot water. The precipitate turned grey-black upon addition of 6M NH3. The student concluded that the unknown contained Hg₂2+ ion. The student received a low mark on the experiment, because the unknown actually contained all three Group I cations. Explain what happened.