Transition elements

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Question 22

Tutton's salts are 'double salts' with the formula $X2Y(ZO4)2⋅6H2O\text{X}_2\text{Y}(\text{ZO}_4)_2 \cdot 6\text{H}_2\text{O}$ .

A Tutton's salt contains two cations: $X+\text{X}^+$ and $Y2+\text{Y}^{2+}$ .

$X+\text{X}^+$ can be an ion of the Group 1 elements $K\text{K}$ , $Rb\text{Rb}$ , $Cs\text{Cs}$ or $Fr\text{Fr}$ , or an ammonium ion ( $NH4+\text{NH}_4^+$ ).
$Y2+\text{Y}^{2+}$ can be a $2 +$ ion of magnesium or an ion of most of the transition elements in Period 4.
$Z\text{Z}$ can be $S\text{S}$ or $Cr\text{Cr}$ .

$(NH4)2Ni(SO4)2⋅6H2O(\text{NH}_4)_2\text{Ni}(\text{SO}_4)_2 \cdot 6\text{H}_2\text{O}$ is an example of a Tutton's salt.

Predict the formula of a Tutton's salt containing different ions from $(NH4)2Ni(SO4)2⋅6H2O(\text{NH}_4)_2\text{Ni}(\text{SO}_4)_2 \cdot 6\text{H}_2\text{O}$ .

[1]

A student prepares a sample of the Tutton's salt, $(NH4)2Ni(SO4)2⋅6H2O(\text{NH}_4)_2\text{Ni}(\text{SO}_4)_2 \cdot 6\text{H}_2\text{O}$ using the method shown below.

Step 1: Dissolve $mol0.015\text{ mol}$ of ammonium sulfate and $mol0.015\text{ mol}$ of hydrated nickel(II) sulfate, $NiSO4⋅6H2O\text{NiSO}_4 \cdot 6\text{H}_2\text{O}$ , in water and make up to $cm350\text{ cm}^3$ .
Step 2: Heat the resulting mixture for 2 minutes and allow to cool.
Step 3: Allow the solvent to evaporate slowly. Green crystals of the Tutton's salt form.

What masses are needed of ammonium sulfate and $NiSO4⋅6H2O\text{NiSO}_4 \cdot 6\text{H}_2\text{O}$ ?

mass of ammonium sulfate
mass of $NiSO4⋅6H2O\text{NiSO}_4 \cdot 6\text{H}_2\text{O}$

[2]

In Step 3, why does the student allow the solvent to evaporate and not boil off all the solvent in Step 2?

[1]

The student dissolves their Tutton's salt in water. A green solution forms.

The student carries out two tests on this aqueous solution.

The student adds an excess of aqueous ammonia to their aqueous solution of Tutton's salt. A blue-violet solution forms.

The complex ion responsible for the blue-violet solution has a molar mass of $mol−1160.9\text{ g mol}^{-1}$ .

Suggest the formula of this complex ion.

[1]

The student adds $NaOH(aq)\text{NaOH(aq)}$ to the aqueous solution of Tutton's salt and warms the mixture.

A precipitate and a gas are formed.

Write the formulae of the precipitate and gas and suggest a test that could confirm the identity of the gas.

Formula of precipitate
Formula of gas
Test to confirm the identity of the gas

[3]

How could the student carry out a test-tube test to confirm the anion in the Tutton's salt?

[2]

Transition elements

Question 22

Transition elements Questions

Transition elements

Question 22

Transition elements Questions