Chemistry help...?

the mineral "Z" is colourless & crystalline and mixed with a red brown solid which does not dissolve in water.

The red brown solid was filtered off and washed.

It dissolved in hot dilute hydrochloric acid but did not effervesce.

The resulting pale yellow solution gave a brown gelatinous precipitate with aqueous sodium hydroxide.

If anyone can help

>identify red brown solid impurity in "Z"

>give the formula of the cation in the red brown solid & pale yellow solution

Thanks!!!

(the flame test colour for "Z" is yellow, I thought the ion present was sodium)

2 Answers

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  • 1 decade ago
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    The red brown solid sounds like iron oxide.

    FeO + 2HCl--->FeCl2 + H20

    FeCl2 +2 NaOH--->Fe(OH)2 + 2NaCl

    Z sounds like a sodium halite

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  • 1 decade ago

    Lancenigo di Villorba (TV), Italy

    Dear Angel,

    I read your question and I write that I thought about it.

    Easily, you have a soli mixture of two chemical compounds.

    Your experiment highlighted a strong difference in nature of two bodies.

    Who preceed me he wrote you that FeO and NaCl would constitue the mixture....I think FeO is wrong.

    I return to your experimental works.

    The mixture exibits a brown substance who is not soluble in water but you made up to dissolve it in acidic preparate.

    Thus, you recover a yellowish solution ; it reacts with alkalies addition and it precipitate a brown jelly.

    Furthermore, you highlighted a strong light during the classical "flame test" for cations. In this moment, I remember not other valuable informations. I want more : you give not me someone information about nature of anions..what are the most diffused? Are they chlorides? Or sulphates? Or nitrates?

    So, I can say you have an oxide hydrated of iron and one compound of Na(I). The iron's oxide hydrated may be Fe(III) hydroxide itself and I say that because it is known some iron's oxides (e.g. the most commons iron's ores, like Fe2O3 "ematite", Fe2O3*H2O "goethite" or Fe2O3*3H2O "limonite") are hard to dissolve them.

    Sorry, I cannot say other.

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